pltcl.c

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/**********************************************************************
 * pltcl.c      - PostgreSQL support for Tcl as
 *                procedural language (PL)
 *
 *    src/pl/tcl/pltcl.c
 *
 **********************************************************************/

#include "postgres.h"

#include <tcl.h>

#include <unistd.h>
#include <fcntl.h>

#include "access/htup_details.h"
#include "access/xact.h"
#include "catalog/objectaccess.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_type.h"
#include "commands/event_trigger.h"
#include "commands/trigger.h"
#include "executor/spi.h"
#include "fmgr.h"
#include "funcapi.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "parser/parse_func.h"
#include "parser/parse_type.h"
#include "pgstat.h"
#include "tcop/tcopprot.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/regproc.h"
#include "utils/rel.h"
#include "utils/syscache.h"
#include "utils/typcache.h"


PG_MODULE_MAGIC;

#define HAVE_TCL_VERSION(maj,min) \
    ((TCL_MAJOR_VERSION > maj) || \
     (TCL_MAJOR_VERSION == maj && TCL_MINOR_VERSION >= min))

/* Insist on Tcl >= 8.4 */
#if !HAVE_TCL_VERSION(8,4)
#error PostgreSQL only supports Tcl 8.4 or later.
#endif

/* Hack to deal with Tcl 8.6 const-ification without losing compatibility */
#ifndef CONST86
#define CONST86
#endif

/* define our text domain for translations */
#undef TEXTDOMAIN
#define TEXTDOMAIN PG_TEXTDOMAIN("pltcl")


/*
 * Support for converting between UTF8 (which is what all strings going into
 * or out of Tcl should be) and the database encoding.
 *
 * If you just use utf_u2e() or utf_e2u() directly, they will leak some
 * palloc'd space when doing a conversion.  This is not worth worrying about
 * if it only happens, say, once per PL/Tcl function call.  If it does seem
 * worth worrying about, use the wrapper macros.
 */

static inline char *
utf_u2e(const char *src)
{
    return pg_any_to_server(src, strlen(src), PG_UTF8);
}

static inline char *
utf_e2u(const char *src)
{
    return pg_server_to_any(src, strlen(src), PG_UTF8);
}

#define UTF_BEGIN \
    do { \
        const char *_pltcl_utf_src = NULL; \
        char *_pltcl_utf_dst = NULL

#define UTF_END \
    if (_pltcl_utf_src != (const char *) _pltcl_utf_dst) \
            pfree(_pltcl_utf_dst); \
    } while (0)

#define UTF_U2E(x) \
    (_pltcl_utf_dst = utf_u2e(_pltcl_utf_src = (x)))

#define UTF_E2U(x) \
    (_pltcl_utf_dst = utf_e2u(_pltcl_utf_src = (x)))


/**********************************************************************
 * Information associated with a Tcl interpreter.  We have one interpreter
 * that is used for all pltclu (untrusted) functions.  For pltcl (trusted)
 * functions, there is a separate interpreter for each effective SQL userid.
 * (This is needed to ensure that an unprivileged user can't inject Tcl code
 * that'll be executed with the privileges of some other SQL user.)
 *
 * The pltcl_interp_desc structs are kept in a Postgres hash table indexed
 * by userid OID, with OID 0 used for the single untrusted interpreter.
 **********************************************************************/
typedef struct pltcl_interp_desc
{
    Oid         user_id;        /* Hash key (must be first!) */
    Tcl_Interp *interp;         /* The interpreter */
    Tcl_HashTable query_hash;   /* pltcl_query_desc structs */
} pltcl_interp_desc;


/**********************************************************************
 * The information we cache about loaded procedures
 *
 * The pltcl_proc_desc struct itself, as well as all subsidiary data,
 * is stored in the memory context identified by the fn_cxt field.
 * We can reclaim all the data by deleting that context, and should do so
 * when the fn_refcount goes to zero.  (But note that we do not bother
 * trying to clean up Tcl's copy of the procedure definition: it's Tcl's
 * problem to manage its memory when we replace a proc definition.  We do
 * not clean up pltcl_proc_descs when a pg_proc row is deleted, only when
 * it is updated, and the same policy applies to Tcl's copy as well.)
 *
 * Note that the data in this struct is shared across all active calls;
 * nothing except the fn_refcount should be changed by a call instance.
 **********************************************************************/
typedef struct pltcl_proc_desc
{
    char       *user_proname;   /* user's name (from pg_proc.proname) */
    char       *internal_proname;   /* Tcl name (based on function OID) */
    MemoryContext fn_cxt;       /* memory context for this procedure */
    unsigned long fn_refcount;  /* number of active references */
    TransactionId fn_xmin;      /* xmin of pg_proc row */
    ItemPointerData fn_tid;     /* TID of pg_proc row */
    bool        fn_readonly;    /* is function readonly? */
    bool        lanpltrusted;   /* is it pltcl (vs. pltclu)? */
    pltcl_interp_desc *interp_desc; /* interpreter to use */
    FmgrInfo    result_in_func; /* input function for fn's result type */
    Oid         result_typioparam;  /* param to pass to same */
    bool        fn_retisset;    /* true if function returns a set */
    bool        fn_retistuple;  /* true if function returns composite */
    int         nargs;          /* number of arguments */
    /* these arrays have nargs entries: */
    FmgrInfo   *arg_out_func;   /* output fns for arg types */
    bool       *arg_is_rowtype; /* is each arg composite? */
} pltcl_proc_desc;


/**********************************************************************
 * The information we cache about prepared and saved plans
 **********************************************************************/
typedef struct pltcl_query_desc
{
    char        qname[20];
    SPIPlanPtr  plan;
    int         nargs;
    Oid        *argtypes;
    FmgrInfo   *arginfuncs;
    Oid        *argtypioparams;
} pltcl_query_desc;


/**********************************************************************
 * For speedy lookup, we maintain a hash table mapping from
 * function OID + trigger flag + user OID to pltcl_proc_desc pointers.
 * The reason the pltcl_proc_desc struct isn't directly part of the hash
 * entry is to simplify recovery from errors during compile_pltcl_function.
 *
 * Note: if the same function is called by multiple userIDs within a session,
 * there will be a separate pltcl_proc_desc entry for each userID in the case
 * of pltcl functions, but only one entry for pltclu functions, because we
 * set user_id = 0 for that case.
 **********************************************************************/
typedef struct pltcl_proc_key
{
    Oid         proc_id;        /* Function OID */

    /*
     * is_trigger is really a bool, but declare as Oid to ensure this struct
     * contains no padding
     */
    Oid         is_trigger;     /* is it a trigger function? */
    Oid         user_id;        /* User calling the function, or 0 */
} pltcl_proc_key;

typedef struct pltcl_proc_ptr
{
    pltcl_proc_key proc_key;    /* Hash key (must be first!) */
    pltcl_proc_desc *proc_ptr;
} pltcl_proc_ptr;


/**********************************************************************
 * Per-call state
 **********************************************************************/
typedef struct pltcl_call_state
{
    /* Call info struct, or NULL in a trigger */
    FunctionCallInfo fcinfo;

    /* Trigger data, if we're in a normal (not event) trigger; else NULL */
    TriggerData *trigdata;

    /* Function we're executing (NULL if not yet identified) */
    pltcl_proc_desc *prodesc;

    /*
     * Information for SRFs and functions returning composite types.
     * ret_tupdesc and attinmeta are set up if either fn_retistuple or
     * fn_retisset, since even a scalar-returning SRF needs a tuplestore.
     */
    TupleDesc   ret_tupdesc;    /* return rowtype, if retistuple or retisset */
    AttInMetadata *attinmeta;   /* metadata for building tuples of that type */

    ReturnSetInfo *rsi;         /* passed-in ReturnSetInfo, if any */
    Tuplestorestate *tuple_store;   /* SRFs accumulate result here */
    MemoryContext tuple_store_cxt;  /* context and resowner for tuplestore */
    ResourceOwner tuple_store_owner;
} pltcl_call_state;


/**********************************************************************
 * Global data
 **********************************************************************/
static char *pltcl_start_proc = NULL;
static char *pltclu_start_proc = NULL;
static bool pltcl_pm_init_done = false;
static Tcl_Interp *pltcl_hold_interp = NULL;
static HTAB *pltcl_interp_htab = NULL;
static HTAB *pltcl_proc_htab = NULL;

/* this is saved and restored by pltcl_handler */
static pltcl_call_state *pltcl_current_call_state = NULL;

/**********************************************************************
 * Lookup table for SQLSTATE condition names
 **********************************************************************/
typedef struct
{
    const char *label;
    int         sqlerrstate;
} TclExceptionNameMap;

static const TclExceptionNameMap exception_name_map[] = {
#include "pltclerrcodes.h"      /* pgrminclude ignore */
    {NULL, 0}
};

/**********************************************************************
 * Forward declarations
 **********************************************************************/
void        _PG_init(void);

static void pltcl_init_interp(pltcl_interp_desc *interp_desc,
                  Oid prolang, bool pltrusted);
static pltcl_interp_desc *pltcl_fetch_interp(Oid prolang, bool pltrusted);
static void call_pltcl_start_proc(Oid prolang, bool pltrusted);
static void start_proc_error_callback(void *arg);

static Datum pltcl_handler(PG_FUNCTION_ARGS, bool pltrusted);

static Datum pltcl_func_handler(PG_FUNCTION_ARGS, pltcl_call_state *call_state,
                   bool pltrusted);
static HeapTuple pltcl_trigger_handler(PG_FUNCTION_ARGS, pltcl_call_state *call_state,
                      bool pltrusted);
static void pltcl_event_trigger_handler(PG_FUNCTION_ARGS, pltcl_call_state *call_state,
                            bool pltrusted);

static void throw_tcl_error(Tcl_Interp *interp, const char *proname);

static pltcl_proc_desc *compile_pltcl_function(Oid fn_oid, Oid tgreloid,
                       bool is_event_trigger,
                       bool pltrusted);

static int pltcl_elog(ClientData cdata, Tcl_Interp *interp,
           int objc, Tcl_Obj *const objv[]);
static void pltcl_construct_errorCode(Tcl_Interp *interp, ErrorData *edata);
static const char *pltcl_get_condition_name(int sqlstate);
static int pltcl_quote(ClientData cdata, Tcl_Interp *interp,
            int objc, Tcl_Obj *const objv[]);
static int pltcl_argisnull(ClientData cdata, Tcl_Interp *interp,
                int objc, Tcl_Obj *const objv[]);
static int pltcl_returnnull(ClientData cdata, Tcl_Interp *interp,
                 int objc, Tcl_Obj *const objv[]);
static int pltcl_returnnext(ClientData cdata, Tcl_Interp *interp,
                 int objc, Tcl_Obj *const objv[]);
static int pltcl_SPI_execute(ClientData cdata, Tcl_Interp *interp,
                  int objc, Tcl_Obj *const objv[]);
static int pltcl_process_SPI_result(Tcl_Interp *interp,
                         const char *arrayname,
                         Tcl_Obj *loop_body,
                         int spi_rc,
                         SPITupleTable *tuptable,
                         uint64 ntuples);
static int pltcl_SPI_prepare(ClientData cdata, Tcl_Interp *interp,
                  int objc, Tcl_Obj *const objv[]);
static int pltcl_SPI_execute_plan(ClientData cdata, Tcl_Interp *interp,
                       int objc, Tcl_Obj *const objv[]);
static int pltcl_SPI_lastoid(ClientData cdata, Tcl_Interp *interp,
                  int objc, Tcl_Obj *const objv[]);
static int pltcl_subtransaction(ClientData cdata, Tcl_Interp *interp,
                     int objc, Tcl_Obj *const objv[]);

static void pltcl_subtrans_begin(MemoryContext oldcontext,
                     ResourceOwner oldowner);
static void pltcl_subtrans_commit(MemoryContext oldcontext,
                      ResourceOwner oldowner);
static void pltcl_subtrans_abort(Tcl_Interp *interp,
                     MemoryContext oldcontext,
                     ResourceOwner oldowner);

static void pltcl_set_tuple_values(Tcl_Interp *interp, const char *arrayname,
                       uint64 tupno, HeapTuple tuple, TupleDesc tupdesc);
static Tcl_Obj *pltcl_build_tuple_argument(HeapTuple tuple, TupleDesc tupdesc);
static HeapTuple pltcl_build_tuple_result(Tcl_Interp *interp,
                         Tcl_Obj **kvObjv, int kvObjc,
                         pltcl_call_state *call_state);
static void pltcl_init_tuple_store(pltcl_call_state *call_state);


/*
 * Hack to override Tcl's builtin Notifier subsystem.  This prevents the
 * backend from becoming multithreaded, which breaks all sorts of things.
 * That happens in the default version of Tcl_InitNotifier if the TCL library
 * has been compiled with multithreading support (i.e. when TCL_THREADS is
 * defined under Unix, and in all cases under Windows).
 * It's okay to disable the notifier because we never enter the Tcl event loop
 * from Postgres, so the notifier capabilities are initialized, but never
 * used.  Only InitNotifier and DeleteFileHandler ever seem to get called
 * within Postgres, but we implement all the functions for completeness.
 */
static ClientData
pltcl_InitNotifier(void)
{
    static int  fakeThreadKey;  /* To give valid address for ClientData */

    return (ClientData) &(fakeThreadKey);
}

static void
pltcl_FinalizeNotifier(ClientData clientData)
{
}

static void
pltcl_SetTimer(CONST86 Tcl_Time *timePtr)
{
}

static void
pltcl_AlertNotifier(ClientData clientData)
{
}

static void
pltcl_CreateFileHandler(int fd, int mask,
                        Tcl_FileProc *proc, ClientData clientData)
{
}

static void
pltcl_DeleteFileHandler(int fd)
{
}

static void
pltcl_ServiceModeHook(int mode)
{
}

static int
pltcl_WaitForEvent(CONST86 Tcl_Time *timePtr)
{
    return 0;
}


/*
 * _PG_init()           - library load-time initialization
 *
 * DO NOT make this static nor change its name!
 *
 * The work done here must be safe to do in the postmaster process,
 * in case the pltcl library is preloaded in the postmaster.
 */
void
_PG_init(void)
{
    Tcl_NotifierProcs notifier;
    HASHCTL     hash_ctl;

    /* Be sure we do initialization only once (should be redundant now) */
    if (pltcl_pm_init_done)
        return;

    pg_bindtextdomain(TEXTDOMAIN);

#ifdef WIN32
    /* Required on win32 to prevent error loading init.tcl */
    Tcl_FindExecutable("");
#endif

    /*
     * Override the functions in the Notifier subsystem.  See comments above.
     */
    notifier.setTimerProc = pltcl_SetTimer;
    notifier.waitForEventProc = pltcl_WaitForEvent;
    notifier.createFileHandlerProc = pltcl_CreateFileHandler;
    notifier.deleteFileHandlerProc = pltcl_DeleteFileHandler;
    notifier.initNotifierProc = pltcl_InitNotifier;
    notifier.finalizeNotifierProc = pltcl_FinalizeNotifier;
    notifier.alertNotifierProc = pltcl_AlertNotifier;
    notifier.serviceModeHookProc = pltcl_ServiceModeHook;
    Tcl_SetNotifier(&notifier);

    /************************************************************
     * Create the dummy hold interpreter to prevent close of
     * stdout and stderr on DeleteInterp
     ************************************************************/
    if ((pltcl_hold_interp = Tcl_CreateInterp()) == NULL)
        elog(ERROR, "could not create master Tcl interpreter");
    if (Tcl_Init(pltcl_hold_interp) == TCL_ERROR)
        elog(ERROR, "could not initialize master Tcl interpreter");

    /************************************************************
     * Create the hash table for working interpreters
     ************************************************************/
    memset(&hash_ctl, 0, sizeof(hash_ctl));
    hash_ctl.keysize = sizeof(Oid);
    hash_ctl.entrysize = sizeof(pltcl_interp_desc);
    pltcl_interp_htab = hash_create("PL/Tcl interpreters",
                                    8,
                                    &hash_ctl,
                                    HASH_ELEM | HASH_BLOBS);

    /************************************************************
     * Create the hash table for function lookup
     ************************************************************/
    memset(&hash_ctl, 0, sizeof(hash_ctl));
    hash_ctl.keysize = sizeof(pltcl_proc_key);
    hash_ctl.entrysize = sizeof(pltcl_proc_ptr);
    pltcl_proc_htab = hash_create("PL/Tcl functions",
                                  100,
                                  &hash_ctl,
                                  HASH_ELEM | HASH_BLOBS);

    /************************************************************
     * Define PL/Tcl's custom GUCs
     ************************************************************/
    DefineCustomStringVariable("pltcl.start_proc",
                               gettext_noop("PL/Tcl function to call once when pltcl is first used."),
                               NULL,
                               &pltcl_start_proc,
                               NULL,
                               PGC_SUSET, 0,
                               NULL, NULL, NULL);
    DefineCustomStringVariable("pltclu.start_proc",
                               gettext_noop("PL/TclU function to call once when pltclu is first used."),
                               NULL,
                               &pltclu_start_proc,
                               NULL,
                               PGC_SUSET, 0,
                               NULL, NULL, NULL);

    pltcl_pm_init_done = true;
}

/**********************************************************************
 * pltcl_init_interp() - initialize a new Tcl interpreter
 **********************************************************************/
static void
pltcl_init_interp(pltcl_interp_desc *interp_desc, Oid prolang, bool pltrusted)
{
    Tcl_Interp *interp;
    char        interpname[32];

    /************************************************************
     * Create the Tcl interpreter as a slave of pltcl_hold_interp.
     * Note: Tcl automatically does Tcl_Init in the untrusted case,
     * and it's not wanted in the trusted case.
     ************************************************************/
    snprintf(interpname, sizeof(interpname), "slave_%u", interp_desc->user_id);
    if ((interp = Tcl_CreateSlave(pltcl_hold_interp, interpname,
                                  pltrusted ? 1 : 0)) == NULL)
        elog(ERROR, "could not create slave Tcl interpreter");

    /************************************************************
     * Initialize the query hash table associated with interpreter
     ************************************************************/
    Tcl_InitHashTable(&interp_desc->query_hash, TCL_STRING_KEYS);

    /************************************************************
     * Install the commands for SPI support in the interpreter
     ************************************************************/
    Tcl_CreateObjCommand(interp, "elog",
                         pltcl_elog, NULL, NULL);
    Tcl_CreateObjCommand(interp, "quote",
                         pltcl_quote, NULL, NULL);
    Tcl_CreateObjCommand(interp, "argisnull",
                         pltcl_argisnull, NULL, NULL);
    Tcl_CreateObjCommand(interp, "return_null",
                         pltcl_returnnull, NULL, NULL);
    Tcl_CreateObjCommand(interp, "return_next",
                         pltcl_returnnext, NULL, NULL);
    Tcl_CreateObjCommand(interp, "spi_exec",
                         pltcl_SPI_execute, NULL, NULL);
    Tcl_CreateObjCommand(interp, "spi_prepare",
                         pltcl_SPI_prepare, NULL, NULL);
    Tcl_CreateObjCommand(interp, "spi_execp",
                         pltcl_SPI_execute_plan, NULL, NULL);
    Tcl_CreateObjCommand(interp, "spi_lastoid",
                         pltcl_SPI_lastoid, NULL, NULL);
    Tcl_CreateObjCommand(interp, "subtransaction",
                         pltcl_subtransaction, NULL, NULL);

    /************************************************************
     * Call the appropriate start_proc, if there is one.
     *
     * We must set interp_desc->interp before the call, else the start_proc
     * won't find the interpreter it's supposed to use.  But, if the
     * start_proc fails, we want to abandon use of the interpreter.
     ************************************************************/
    PG_TRY();
    {
        interp_desc->interp = interp;
        call_pltcl_start_proc(prolang, pltrusted);
    }
    PG_CATCH();
    {
        interp_desc->interp = NULL;
        Tcl_DeleteInterp(interp);
        PG_RE_THROW();
    }
    PG_END_TRY();
}

/**********************************************************************
 * pltcl_fetch_interp() - fetch the Tcl interpreter to use for a function
 *
 * This also takes care of any on-first-use initialization required.
 **********************************************************************/
static pltcl_interp_desc *
pltcl_fetch_interp(Oid prolang, bool pltrusted)
{
    Oid         user_id;
    pltcl_interp_desc *interp_desc;
    bool        found;

    /* Find or create the interpreter hashtable entry for this userid */
    if (pltrusted)
        user_id = GetUserId();
    else
        user_id = InvalidOid;

    interp_desc = hash_search(pltcl_interp_htab, &user_id,
                              HASH_ENTER,
                              &found);
    if (!found)
        interp_desc->interp = NULL;

    /* If we haven't yet successfully made an interpreter, try to do that */
    if (!interp_desc->interp)
        pltcl_init_interp(interp_desc, prolang, pltrusted);

    return interp_desc;
}


/**********************************************************************
 * call_pltcl_start_proc()   - Call user-defined initialization proc, if any
 **********************************************************************/
static void
call_pltcl_start_proc(Oid prolang, bool pltrusted)
{
    char       *start_proc;
    const char *gucname;
    ErrorContextCallback errcallback;
    List       *namelist;
    Oid         fargtypes[1];   /* dummy */
    Oid         procOid;
    HeapTuple   procTup;
    Form_pg_proc procStruct;
    AclResult   aclresult;
    FmgrInfo    finfo;
    FunctionCallInfoData fcinfo;
    PgStat_FunctionCallUsage fcusage;

    /* select appropriate GUC */
    start_proc = pltrusted ? pltcl_start_proc : pltclu_start_proc;
    gucname = pltrusted ? "pltcl.start_proc" : "pltclu.start_proc";

    /* Nothing to do if it's empty or unset */
    if (start_proc == NULL || start_proc[0] == '\0')
        return;

    /* Set up errcontext callback to make errors more helpful */
    errcallback.callback = start_proc_error_callback;
    errcallback.arg = (void *) gucname;
    errcallback.previous = error_context_stack;
    error_context_stack = &errcallback;

    /* Parse possibly-qualified identifier and look up the function */
    namelist = stringToQualifiedNameList(start_proc);
    procOid = LookupFuncName(namelist, 0, fargtypes, false);

    /* Current user must have permission to call function */
    aclresult = pg_proc_aclcheck(procOid, GetUserId(), ACL_EXECUTE);
    if (aclresult != ACLCHECK_OK)
        aclcheck_error(aclresult, ACL_KIND_PROC, start_proc);

    /* Get the function's pg_proc entry */
    procTup = SearchSysCache1(PROCOID, ObjectIdGetDatum(procOid));
    if (!HeapTupleIsValid(procTup))
        elog(ERROR, "cache lookup failed for function %u", procOid);
    procStruct = (Form_pg_proc) GETSTRUCT(procTup);

    /* It must be same language as the function we're currently calling */
    if (procStruct->prolang != prolang)
        ereport(ERROR,
                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                 errmsg("function \"%s\" is in the wrong language",
                        start_proc)));

    /*
     * It must not be SECURITY DEFINER, either.  This together with the
     * language match check ensures that the function will execute in the same
     * Tcl interpreter we just finished initializing.
     */
    if (procStruct->prosecdef)
        ereport(ERROR,
                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                 errmsg("function \"%s\" must not be SECURITY DEFINER",
                        start_proc)));

    /* A-OK */
    ReleaseSysCache(procTup);

    /*
     * Call the function using the normal SQL function call mechanism.  We
     * could perhaps cheat and jump directly to pltcl_handler(), but it seems
     * better to do it this way so that the call is exposed to, eg, call
     * statistics collection.
     */
    InvokeFunctionExecuteHook(procOid);
    fmgr_info(procOid, &finfo);
    InitFunctionCallInfoData(fcinfo, &finfo,
                             0,
                             InvalidOid, NULL, NULL);
    pgstat_init_function_usage(&fcinfo, &fcusage);
    (void) FunctionCallInvoke(&fcinfo);
    pgstat_end_function_usage(&fcusage, true);

    /* Pop the error context stack */
    error_context_stack = errcallback.previous;
}

/*
 * Error context callback for errors occurring during start_proc processing.
 */
static void
start_proc_error_callback(void *arg)
{
    const char *gucname = (const char *) arg;

    /* translator: %s is "pltcl.start_proc" or "pltclu.start_proc" */
    errcontext("processing %s parameter", gucname);
}


/**********************************************************************
 * pltcl_call_handler       - This is the only visible function
 *                of the PL interpreter. The PostgreSQL
 *                function manager and trigger manager
 *                call this function for execution of
 *                PL/Tcl procedures.
 **********************************************************************/
PG_FUNCTION_INFO_V1(pltcl_call_handler);

/* keep non-static */
Datum
pltcl_call_handler(PG_FUNCTION_ARGS)
{
    return pltcl_handler(fcinfo, true);
}

/*
 * Alternative handler for unsafe functions
 */
PG_FUNCTION_INFO_V1(pltclu_call_handler);

/* keep non-static */
Datum
pltclu_call_handler(PG_FUNCTION_ARGS)
{
    return pltcl_handler(fcinfo, false);
}


/**********************************************************************
 * pltcl_handler()      - Handler for function and trigger calls, for
 *                        both trusted and untrusted interpreters.
 **********************************************************************/
static Datum
pltcl_handler(PG_FUNCTION_ARGS, bool pltrusted)
{
    Datum       retval;
    pltcl_call_state current_call_state;
    pltcl_call_state *save_call_state;

    /*
     * Initialize current_call_state to nulls/zeroes; in particular, set its
     * prodesc pointer to null.  Anything that sets it non-null should
     * increase the prodesc's fn_refcount at the same time.  We'll decrease
     * the refcount, and then delete the prodesc if it's no longer referenced,
     * on the way out of this function.  This ensures that prodescs live as
     * long as needed even if somebody replaces the originating pg_proc row
     * while they're executing.
     */
    memset(&current_call_state, 0, sizeof(current_call_state));

    /*
     * Ensure that static pointer is saved/restored properly
     */
    save_call_state = pltcl_current_call_state;
    pltcl_current_call_state = &current_call_state;

    PG_TRY();
    {
        /*
         * Determine if called as function or trigger and call appropriate
         * subhandler
         */
        if (CALLED_AS_TRIGGER(fcinfo))
        {
            /* invoke the trigger handler */
            retval = PointerGetDatum(pltcl_trigger_handler(fcinfo,
                                                           &current_call_state,
                                                           pltrusted));
        }
        else if (CALLED_AS_EVENT_TRIGGER(fcinfo))
        {
            /* invoke the event trigger handler */
            pltcl_event_trigger_handler(fcinfo, &current_call_state, pltrusted);
            retval = (Datum) 0;
        }
        else
        {
            /* invoke the regular function handler */
            current_call_state.fcinfo = fcinfo;
            retval = pltcl_func_handler(fcinfo, &current_call_state, pltrusted);
        }
    }
    PG_CATCH();
    {
        /* Restore static pointer, then clean up the prodesc refcount if any */
        pltcl_current_call_state = save_call_state;
        if (current_call_state.prodesc != NULL)
        {
            Assert(current_call_state.prodesc->fn_refcount > 0);
            if (--current_call_state.prodesc->fn_refcount == 0)
                MemoryContextDelete(current_call_state.prodesc->fn_cxt);
        }
        PG_RE_THROW();
    }
    PG_END_TRY();

    /* Restore static pointer, then clean up the prodesc refcount if any */
    /* (We're being paranoid in case an error is thrown in context deletion) */
    pltcl_current_call_state = save_call_state;
    if (current_call_state.prodesc != NULL)
    {
        Assert(current_call_state.prodesc->fn_refcount > 0);
        if (--current_call_state.prodesc->fn_refcount == 0)
            MemoryContextDelete(current_call_state.prodesc->fn_cxt);
    }

    return retval;
}


/**********************************************************************
 * pltcl_func_handler()     - Handler for regular function calls
 **********************************************************************/
static Datum
pltcl_func_handler(PG_FUNCTION_ARGS, pltcl_call_state *call_state,
                   bool pltrusted)
{
    pltcl_proc_desc *prodesc;
    Tcl_Interp *volatile interp;
    Tcl_Obj    *tcl_cmd;
    int         i;
    int         tcl_rc;
    Datum       retval;

    /* Connect to SPI manager */
    if (SPI_connect() != SPI_OK_CONNECT)
        elog(ERROR, "could not connect to SPI manager");

    /* Find or compile the function */
    prodesc = compile_pltcl_function(fcinfo->flinfo->fn_oid, InvalidOid,
                                     false, pltrusted);

    call_state->prodesc = prodesc;
    prodesc->fn_refcount++;

    interp = prodesc->interp_desc->interp;

    /*
     * If we're a SRF, check caller can handle materialize mode, and save
     * relevant info into call_state.  We must ensure that the returned
     * tuplestore is owned by the caller's context, even if we first create it
     * inside a subtransaction.
     */
    if (prodesc->fn_retisset)
    {
        ReturnSetInfo *rsi = (ReturnSetInfo *) fcinfo->resultinfo;

        if (!rsi || !IsA(rsi, ReturnSetInfo) ||
            (rsi->allowedModes & SFRM_Materialize) == 0)
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("set-valued function called in context that cannot accept a set")));

        call_state->rsi = rsi;
        call_state->tuple_store_cxt = rsi->econtext->ecxt_per_query_memory;
        call_state->tuple_store_owner = CurrentResourceOwner;
    }

    /************************************************************
     * Create the tcl command to call the internal
     * proc in the Tcl interpreter
     ************************************************************/
    tcl_cmd = Tcl_NewObj();
    Tcl_ListObjAppendElement(NULL, tcl_cmd,
                             Tcl_NewStringObj(prodesc->internal_proname, -1));

    /* We hold a refcount on tcl_cmd just to be sure it stays around */
    Tcl_IncrRefCount(tcl_cmd);

    /************************************************************
     * Add all call arguments to the command
     ************************************************************/
    PG_TRY();
    {
        for (i = 0; i < prodesc->nargs; i++)
        {
            if (prodesc->arg_is_rowtype[i])
            {
                /**************************************************
                 * For tuple values, add a list for 'array set ...'
                 **************************************************/
                if (fcinfo->argnull[i])
                    Tcl_ListObjAppendElement(NULL, tcl_cmd, Tcl_NewObj());
                else
                {
                    HeapTupleHeader td;
                    Oid         tupType;
                    int32       tupTypmod;
                    TupleDesc   tupdesc;
                    HeapTupleData tmptup;
                    Tcl_Obj    *list_tmp;

                    td = DatumGetHeapTupleHeader(fcinfo->arg[i]);
                    /* Extract rowtype info and find a tupdesc */
                    tupType = HeapTupleHeaderGetTypeId(td);
                    tupTypmod = HeapTupleHeaderGetTypMod(td);
                    tupdesc = lookup_rowtype_tupdesc(tupType, tupTypmod);
                    /* Build a temporary HeapTuple control structure */
                    tmptup.t_len = HeapTupleHeaderGetDatumLength(td);
                    tmptup.t_data = td;

                    list_tmp = pltcl_build_tuple_argument(&tmptup, tupdesc);
                    Tcl_ListObjAppendElement(NULL, tcl_cmd, list_tmp);

                    ReleaseTupleDesc(tupdesc);
                }
            }
            else
            {
                /**************************************************
                 * Single values are added as string element
                 * of their external representation
                 **************************************************/
                if (fcinfo->argnull[i])
                    Tcl_ListObjAppendElement(NULL, tcl_cmd, Tcl_NewObj());
                else
                {
                    char       *tmp;

                    tmp = OutputFunctionCall(&prodesc->arg_out_func[i],
                                             fcinfo->arg[i]);
                    UTF_BEGIN;
                    Tcl_ListObjAppendElement(NULL, tcl_cmd,
                                             Tcl_NewStringObj(UTF_E2U(tmp), -1));
                    UTF_END;
                    pfree(tmp);
                }
            }
        }
    }
    PG_CATCH();
    {
        /* Release refcount to free tcl_cmd */
        Tcl_DecrRefCount(tcl_cmd);
        PG_RE_THROW();
    }
    PG_END_TRY();

    /************************************************************
     * Call the Tcl function
     *
     * We assume no PG error can be thrown directly from this call.
     ************************************************************/
    tcl_rc = Tcl_EvalObjEx(interp, tcl_cmd, (TCL_EVAL_DIRECT | TCL_EVAL_GLOBAL));

    /* Release refcount to free tcl_cmd (and all subsidiary objects) */
    Tcl_DecrRefCount(tcl_cmd);

    /************************************************************
     * Check for errors reported by Tcl.
     ************************************************************/
    if (tcl_rc != TCL_OK)
        throw_tcl_error(interp, prodesc->user_proname);

    /************************************************************
     * Disconnect from SPI manager and then create the return
     * value datum (if the input function does a palloc for it
     * this must not be allocated in the SPI memory context
     * because SPI_finish would free it).  But don't try to call
     * the result_in_func if we've been told to return a NULL;
     * the Tcl result may not be a valid value of the result type
     * in that case.
     ************************************************************/
    if (SPI_finish() != SPI_OK_FINISH)
        elog(ERROR, "SPI_finish() failed");

    if (prodesc->fn_retisset)
    {
        ReturnSetInfo *rsi = call_state->rsi;

        /* We already checked this is OK */
        rsi->returnMode = SFRM_Materialize;

        /* If we produced any tuples, send back the result */
        if (call_state->tuple_store)
        {
            rsi->setResult = call_state->tuple_store;
            if (call_state->ret_tupdesc)
            {
                MemoryContext oldcxt;

                oldcxt = MemoryContextSwitchTo(call_state->tuple_store_cxt);
                rsi->setDesc = CreateTupleDescCopy(call_state->ret_tupdesc);
                MemoryContextSwitchTo(oldcxt);
            }
        }
        retval = (Datum) 0;
        fcinfo->isnull = true;
    }
    else if (fcinfo->isnull)
    {
        retval = InputFunctionCall(&prodesc->result_in_func,
                                   NULL,
                                   prodesc->result_typioparam,
                                   -1);
    }
    else if (prodesc->fn_retistuple)
    {
        TupleDesc   td;
        HeapTuple   tup;
        Tcl_Obj    *resultObj;
        Tcl_Obj   **resultObjv;
        int         resultObjc;

        /*
         * Set up data about result type.  XXX it's tempting to consider
         * caching this in the prodesc, in the common case where the rowtype
         * is determined by the function not the calling query.  But we'd have
         * to be able to deal with ADD/DROP/ALTER COLUMN events when the
         * result type is a named composite type, so it's not exactly trivial.
         * Maybe worth improving someday.
         */
        if (get_call_result_type(fcinfo, NULL, &td) != TYPEFUNC_COMPOSITE)
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("function returning record called in context "
                            "that cannot accept type record")));

        Assert(!call_state->ret_tupdesc);
        Assert(!call_state->attinmeta);
        call_state->ret_tupdesc = td;
        call_state->attinmeta = TupleDescGetAttInMetadata(td);

        /* Convert function result to tuple */
        resultObj = Tcl_GetObjResult(interp);
        if (Tcl_ListObjGetElements(interp, resultObj, &resultObjc, &resultObjv) == TCL_ERROR)
            throw_tcl_error(interp, prodesc->user_proname);

        tup = pltcl_build_tuple_result(interp, resultObjv, resultObjc,
                                       call_state);
        retval = HeapTupleGetDatum(tup);
    }
    else
        retval = InputFunctionCall(&prodesc->result_in_func,
                                   utf_u2e(Tcl_GetStringResult(interp)),
                                   prodesc->result_typioparam,
                                   -1);

    return retval;
}


/**********************************************************************
 * pltcl_trigger_handler()  - Handler for trigger calls
 **********************************************************************/
static HeapTuple
pltcl_trigger_handler(PG_FUNCTION_ARGS, pltcl_call_state *call_state,
                      bool pltrusted)
{
    pltcl_proc_desc *prodesc;
    Tcl_Interp *volatile interp;
    TriggerData *trigdata = (TriggerData *) fcinfo->context;
    char       *stroid;
    TupleDesc   tupdesc;
    volatile HeapTuple rettup;
    Tcl_Obj    *tcl_cmd;
    Tcl_Obj    *tcl_trigtup;
    Tcl_Obj    *tcl_newtup;
    int         tcl_rc;
    int         i;
    const char *result;
    int         result_Objc;
    Tcl_Obj   **result_Objv;
    int         rc PG_USED_FOR_ASSERTS_ONLY;

    call_state->trigdata = trigdata;

    /* Connect to SPI manager */
    if (SPI_connect() != SPI_OK_CONNECT)
        elog(ERROR, "could not connect to SPI manager");

    /* Make transition tables visible to this SPI connection */
    rc = SPI_register_trigger_data(trigdata);
    Assert(rc >= 0);

    /* Find or compile the function */
    prodesc = compile_pltcl_function(fcinfo->flinfo->fn_oid,
                                     RelationGetRelid(trigdata->tg_relation),
                                     false, /* not an event trigger */
                                     pltrusted);

    call_state->prodesc = prodesc;
    prodesc->fn_refcount++;

    interp = prodesc->interp_desc->interp;

    tupdesc = RelationGetDescr(trigdata->tg_relation);

    /************************************************************
     * Create the tcl command to call the internal
     * proc in the interpreter
     ************************************************************/
    tcl_cmd = Tcl_NewObj();
    Tcl_IncrRefCount(tcl_cmd);

    PG_TRY();
    {
        /* The procedure name (note this is all ASCII, so no utf_e2u) */
        Tcl_ListObjAppendElement(NULL, tcl_cmd,
                                 Tcl_NewStringObj(prodesc->internal_proname, -1));

        /* The trigger name for argument TG_name */
        Tcl_ListObjAppendElement(NULL, tcl_cmd,
                                 Tcl_NewStringObj(utf_e2u(trigdata->tg_trigger->tgname), -1));

        /* The oid of the trigger relation for argument TG_relid */
        /* Consider not converting to a string for more performance? */
        stroid = DatumGetCString(DirectFunctionCall1(oidout,
                                                     ObjectIdGetDatum(trigdata->tg_relation->rd_id)));
        Tcl_ListObjAppendElement(NULL, tcl_cmd,
                                 Tcl_NewStringObj(stroid, -1));
        pfree(stroid);

        /* The name of the table the trigger is acting on: TG_table_name */
        stroid = SPI_getrelname(trigdata->tg_relation);
        Tcl_ListObjAppendElement(NULL, tcl_cmd,
                                 Tcl_NewStringObj(utf_e2u(stroid), -1));
        pfree(stroid);

        /* The schema of the table the trigger is acting on: TG_table_schema */
        stroid = SPI_getnspname(trigdata->tg_relation);
        Tcl_ListObjAppendElement(NULL, tcl_cmd,
                                 Tcl_NewStringObj(utf_e2u(stroid), -1));
        pfree(stroid);

        /* A list of attribute names for argument TG_relatts */
        tcl_trigtup = Tcl_NewObj();
        Tcl_ListObjAppendElement(NULL, tcl_trigtup, Tcl_NewObj());
        for (i = 0; i < tupdesc->natts; i++)
        {
            if (tupdesc->attrs[i]->attisdropped)
                Tcl_ListObjAppendElement(NULL, tcl_trigtup, Tcl_NewObj());
            else
                Tcl_ListObjAppendElement(NULL, tcl_trigtup,
                                         Tcl_NewStringObj(utf_e2u(NameStr(tupdesc->attrs[i]->attname)), -1));
        }
        Tcl_ListObjAppendElement(NULL, tcl_cmd, tcl_trigtup);

        /* The when part of the event for TG_when */
        if (TRIGGER_FIRED_BEFORE(trigdata->tg_event))
            Tcl_ListObjAppendElement(NULL, tcl_cmd,
                                     Tcl_NewStringObj("BEFORE", -1));
        else if (TRIGGER_FIRED_AFTER(trigdata->tg_event))
            Tcl_ListObjAppendElement(NULL, tcl_cmd,
                                     Tcl_NewStringObj("AFTER", -1));
        else if (TRIGGER_FIRED_INSTEAD(trigdata->tg_event))
            Tcl_ListObjAppendElement(NULL, tcl_cmd,
                                     Tcl_NewStringObj("INSTEAD OF", -1));
        else
            elog(ERROR, "unrecognized WHEN tg_event: %u", trigdata->tg_event);

        /* The level part of the event for TG_level */
        if (TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
        {
            Tcl_ListObjAppendElement(NULL, tcl_cmd,
                                     Tcl_NewStringObj("ROW", -1));

            /* Build the data list for the trigtuple */
            tcl_trigtup = pltcl_build_tuple_argument(trigdata->tg_trigtuple,
                                                     tupdesc);

            /*
             * Now the command part of the event for TG_op and data for NEW
             * and OLD
             */
            if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
            {
                Tcl_ListObjAppendElement(NULL, tcl_cmd,
                                         Tcl_NewStringObj("INSERT", -1));

                Tcl_ListObjAppendElement(NULL, tcl_cmd, tcl_trigtup);
                Tcl_ListObjAppendElement(NULL, tcl_cmd, Tcl_NewObj());

                rettup = trigdata->tg_trigtuple;
            }
            else if (TRIGGER_FIRED_BY_DELETE(trigdata->tg_event))
            {
                Tcl_ListObjAppendElement(NULL, tcl_cmd,
                                         Tcl_NewStringObj("DELETE", -1));

                Tcl_ListObjAppendElement(NULL, tcl_cmd, Tcl_NewObj());
                Tcl_ListObjAppendElement(NULL, tcl_cmd, tcl_trigtup);

                rettup = trigdata->tg_trigtuple;
            }
            else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
            {
                Tcl_ListObjAppendElement(NULL, tcl_cmd,
                                         Tcl_NewStringObj("UPDATE", -1));

                tcl_newtup = pltcl_build_tuple_argument(trigdata->tg_newtuple,
                                                        tupdesc);

                Tcl_ListObjAppendElement(NULL, tcl_cmd, tcl_newtup);
                Tcl_ListObjAppendElement(NULL, tcl_cmd, tcl_trigtup);

                rettup = trigdata->tg_newtuple;
            }
            else
                elog(ERROR, "unrecognized OP tg_event: %u", trigdata->tg_event);
        }
        else if (TRIGGER_FIRED_FOR_STATEMENT(trigdata->tg_event))
        {
            Tcl_ListObjAppendElement(NULL, tcl_cmd,
                                     Tcl_NewStringObj("STATEMENT", -1));

            if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
                Tcl_ListObjAppendElement(NULL, tcl_cmd,
                                         Tcl_NewStringObj("INSERT", -1));
            else if (TRIGGER_FIRED_BY_DELETE(trigdata->tg_event))
                Tcl_ListObjAppendElement(NULL, tcl_cmd,
                                         Tcl_NewStringObj("DELETE", -1));
            else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
                Tcl_ListObjAppendElement(NULL, tcl_cmd,
                                         Tcl_NewStringObj("UPDATE", -1));
            else if (TRIGGER_FIRED_BY_TRUNCATE(trigdata->tg_event))
                Tcl_ListObjAppendElement(NULL, tcl_cmd,
                                         Tcl_NewStringObj("TRUNCATE", -1));
            else
                elog(ERROR, "unrecognized OP tg_event: %u", trigdata->tg_event);

            Tcl_ListObjAppendElement(NULL, tcl_cmd, Tcl_NewObj());
            Tcl_ListObjAppendElement(NULL, tcl_cmd, Tcl_NewObj());

            rettup = (HeapTuple) NULL;
        }
        else
            elog(ERROR, "unrecognized LEVEL tg_event: %u", trigdata->tg_event);

        /* Finally append the arguments from CREATE TRIGGER */
        for (i = 0; i < trigdata->tg_trigger->tgnargs; i++)
            Tcl_ListObjAppendElement(NULL, tcl_cmd,
                                     Tcl_NewStringObj(utf_e2u(trigdata->tg_trigger->tgargs[i]), -1));

    }
    PG_CATCH();
    {
        Tcl_DecrRefCount(tcl_cmd);
        PG_RE_THROW();
    }
    PG_END_TRY();

    /************************************************************
     * Call the Tcl function
     *
     * We assume no PG error can be thrown directly from this call.
     ************************************************************/
    tcl_rc = Tcl_EvalObjEx(interp, tcl_cmd, (TCL_EVAL_DIRECT | TCL_EVAL_GLOBAL));

    /* Release refcount to free tcl_cmd (and all subsidiary objects) */
    Tcl_DecrRefCount(tcl_cmd);

    /************************************************************
     * Check for errors reported by Tcl.
     ************************************************************/
    if (tcl_rc != TCL_OK)
        throw_tcl_error(interp, prodesc->user_proname);

    /************************************************************
     * Exit SPI environment.
     ************************************************************/
    if (SPI_finish() != SPI_OK_FINISH)
        elog(ERROR, "SPI_finish() failed");

    /************************************************************
     * The return value from the procedure might be one of
     * the magic strings OK or SKIP, or a list from array get.
     * We can check for OK or SKIP without worrying about encoding.
     ************************************************************/
    result = Tcl_GetStringResult(interp);

    if (strcmp(result, "OK") == 0)
        return rettup;
    if (strcmp(result, "SKIP") == 0)
        return (HeapTuple) NULL;

    /************************************************************
     * Otherwise, the return value should be a column name/value list
     * specifying the modified tuple to return.
     ************************************************************/
    if (Tcl_ListObjGetElements(interp, Tcl_GetObjResult(interp),
                               &result_Objc, &result_Objv) != TCL_OK)
        ereport(ERROR,
                (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
                 errmsg("could not split return value from trigger: %s",
                        utf_u2e(Tcl_GetStringResult(interp)))));

    /* Convert function result to tuple */
    rettup = pltcl_build_tuple_result(interp, result_Objv, result_Objc,
                                      call_state);

    return rettup;
}

/**********************************************************************
 * pltcl_event_trigger_handler()    - Handler for event trigger calls
 **********************************************************************/
static void
pltcl_event_trigger_handler(PG_FUNCTION_ARGS, pltcl_call_state *call_state,
                            bool pltrusted)
{
    pltcl_proc_desc *prodesc;
    Tcl_Interp *volatile interp;
    EventTriggerData *tdata = (EventTriggerData *) fcinfo->context;
    Tcl_Obj    *tcl_cmd;
    int         tcl_rc;

    /* Connect to SPI manager */
    if (SPI_connect() != SPI_OK_CONNECT)
        elog(ERROR, "could not connect to SPI manager");

    /* Find or compile the function */
    prodesc = compile_pltcl_function(fcinfo->flinfo->fn_oid,
                                     InvalidOid, true, pltrusted);

    call_state->prodesc = prodesc;
    prodesc->fn_refcount++;

    interp = prodesc->interp_desc->interp;

    /* Create the tcl command and call the internal proc */
    tcl_cmd = Tcl_NewObj();
    Tcl_IncrRefCount(tcl_cmd);
    Tcl_ListObjAppendElement(NULL, tcl_cmd,
                             Tcl_NewStringObj(prodesc->internal_proname, -1));
    Tcl_ListObjAppendElement(NULL, tcl_cmd,
                             Tcl_NewStringObj(utf_e2u(tdata->event), -1));
    Tcl_ListObjAppendElement(NULL, tcl_cmd,
                             Tcl_NewStringObj(utf_e2u(tdata->tag), -1));

    tcl_rc = Tcl_EvalObjEx(interp, tcl_cmd, (TCL_EVAL_DIRECT | TCL_EVAL_GLOBAL));

    /* Release refcount to free tcl_cmd (and all subsidiary objects) */
    Tcl_DecrRefCount(tcl_cmd);

    /* Check for errors reported by Tcl. */
    if (tcl_rc != TCL_OK)
        throw_tcl_error(interp, prodesc->user_proname);

    if (SPI_finish() != SPI_OK_FINISH)
        elog(ERROR, "SPI_finish() failed");
}


/**********************************************************************
 * throw_tcl_error  - ereport an error returned from the Tcl interpreter
 **********************************************************************/
static void
throw_tcl_error(Tcl_Interp *interp, const char *proname)
{
    /*
     * Caution is needed here because Tcl_GetVar could overwrite the
     * interpreter result (even though it's not really supposed to), and we
     * can't control the order of evaluation of ereport arguments. Hence, make
     * real sure we have our own copy of the result string before invoking
     * Tcl_GetVar.
     */
    char       *emsg;
    char       *econtext;

    emsg = pstrdup(utf_u2e(Tcl_GetStringResult(interp)));
    econtext = utf_u2e(Tcl_GetVar(interp, "errorInfo", TCL_GLOBAL_ONLY));
    ereport(ERROR,
            (errcode(ERRCODE_EXTERNAL_ROUTINE_EXCEPTION),
             errmsg("%s", emsg),
             errcontext("%s\nin PL/Tcl function \"%s\"",
                        econtext, proname)));
}


/**********************************************************************
 * compile_pltcl_function   - compile (or hopefully just look up) function
 *
 * tgreloid is the OID of the relation when compiling a trigger, or zero
 * (InvalidOid) when compiling a plain function.
 **********************************************************************/
static pltcl_proc_desc *
compile_pltcl_function(Oid fn_oid, Oid tgreloid,
                       bool is_event_trigger, bool pltrusted)
{
    HeapTuple   procTup;
    Form_pg_proc procStruct;
    pltcl_proc_key proc_key;
    pltcl_proc_ptr *proc_ptr;
    bool        found;
    pltcl_proc_desc *prodesc;
    pltcl_proc_desc *old_prodesc;
    volatile MemoryContext proc_cxt = NULL;
    Tcl_DString proc_internal_def;
    Tcl_DString proc_internal_body;

    /* We'll need the pg_proc tuple in any case... */
    procTup = SearchSysCache1(PROCOID, ObjectIdGetDatum(fn_oid));
    if (!HeapTupleIsValid(procTup))
        elog(ERROR, "cache lookup failed for function %u", fn_oid);
    procStruct = (Form_pg_proc) GETSTRUCT(procTup);

    /*
     * Look up function in pltcl_proc_htab; if it's not there, create an entry
     * and set the entry's proc_ptr to NULL.
     */
    proc_key.proc_id = fn_oid;
    proc_key.is_trigger = OidIsValid(tgreloid);
    proc_key.user_id = pltrusted ? GetUserId() : InvalidOid;

    proc_ptr = hash_search(pltcl_proc_htab, &proc_key,
                           HASH_ENTER,
                           &found);
    if (!found)
        proc_ptr->proc_ptr = NULL;

    prodesc = proc_ptr->proc_ptr;

    /************************************************************
     * If it's present, must check whether it's still up to date.
     * This is needed because CREATE OR REPLACE FUNCTION can modify the
     * function's pg_proc entry without changing its OID.
     ************************************************************/
    if (prodesc != NULL &&
        prodesc->fn_xmin == HeapTupleHeaderGetRawXmin(procTup->t_data) &&
        ItemPointerEquals(&prodesc->fn_tid, &procTup->t_self))
    {
        /* It's still up-to-date, so we can use it */
        ReleaseSysCache(procTup);
        return prodesc;
    }

    /************************************************************
     * If we haven't found it in the hashtable, we analyze
     * the functions arguments and returntype and store
     * the in-/out-functions in the prodesc block and create
     * a new hashtable entry for it.
     *
     * Then we load the procedure into the Tcl interpreter.
     ************************************************************/
    Tcl_DStringInit(&proc_internal_def);
    Tcl_DStringInit(&proc_internal_body);
    PG_TRY();
    {
        bool        is_trigger = OidIsValid(tgreloid);
        char        internal_proname[128];
        HeapTuple   typeTup;
        Form_pg_type typeStruct;
        char        proc_internal_args[33 * FUNC_MAX_ARGS];
        Datum       prosrcdatum;
        bool        isnull;
        char       *proc_source;
        char        buf[32];
        Tcl_Interp *interp;
        int         i;
        int         tcl_rc;
        MemoryContext oldcontext;

        /************************************************************
         * Build our internal proc name from the function's Oid.  Append
         * "_trigger" when appropriate to ensure the normal and trigger
         * cases are kept separate.  Note name must be all-ASCII.
         ************************************************************/
        if (is_event_trigger)
            snprintf(internal_proname, sizeof(internal_proname),
                     "__PLTcl_proc_%u_evttrigger", fn_oid);
        else if (is_trigger)
            snprintf(internal_proname, sizeof(internal_proname),
                     "__PLTcl_proc_%u_trigger", fn_oid);
        else
            snprintf(internal_proname, sizeof(internal_proname),
                     "__PLTcl_proc_%u", fn_oid);

        /************************************************************
         * Allocate a context that will hold all PG data for the procedure.
         * We use the internal proc name as the context name.
         ************************************************************/
        proc_cxt = AllocSetContextCreate(TopMemoryContext,
                                         internal_proname,
                                         ALLOCSET_SMALL_SIZES);

        /************************************************************
         * Allocate and fill a new procedure description block.
         * struct prodesc and subsidiary data must all live in proc_cxt.
         ************************************************************/
        oldcontext = MemoryContextSwitchTo(proc_cxt);
        prodesc = (pltcl_proc_desc *) palloc0(sizeof(pltcl_proc_desc));
        prodesc->user_proname = pstrdup(NameStr(procStruct->proname));
        prodesc->internal_proname = pstrdup(internal_proname);
        prodesc->fn_cxt = proc_cxt;
        prodesc->fn_refcount = 0;
        prodesc->fn_xmin = HeapTupleHeaderGetRawXmin(procTup->t_data);
        prodesc->fn_tid = procTup->t_self;
        prodesc->nargs = procStruct->pronargs;
        prodesc->arg_out_func = (FmgrInfo *) palloc0(prodesc->nargs * sizeof(FmgrInfo));
        prodesc->arg_is_rowtype = (bool *) palloc0(prodesc->nargs * sizeof(bool));
        MemoryContextSwitchTo(oldcontext);

        /* Remember if function is STABLE/IMMUTABLE */
        prodesc->fn_readonly =
            (procStruct->provolatile != PROVOLATILE_VOLATILE);
        /* And whether it is trusted */
        prodesc->lanpltrusted = pltrusted;

        /************************************************************
         * Identify the interpreter to use for the function
         ************************************************************/
        prodesc->interp_desc = pltcl_fetch_interp(procStruct->prolang,
                                                  prodesc->lanpltrusted);
        interp = prodesc->interp_desc->interp;

        /************************************************************
         * Get the required information for input conversion of the
         * return value.
         ************************************************************/
        if (!is_trigger && !is_event_trigger)
        {
            typeTup =
                SearchSysCache1(TYPEOID,
                                ObjectIdGetDatum(procStruct->prorettype));
            if (!HeapTupleIsValid(typeTup))
                elog(ERROR, "cache lookup failed for type %u",
                     procStruct->prorettype);
            typeStruct = (Form_pg_type) GETSTRUCT(typeTup);

            /* Disallow pseudotype result, except VOID and RECORD */
            if (typeStruct->typtype == TYPTYPE_PSEUDO)
            {
                if (procStruct->prorettype == VOIDOID ||
                    procStruct->prorettype == RECORDOID)
                     /* okay */ ;
                else if (procStruct->prorettype == TRIGGEROID ||
                         procStruct->prorettype == EVTTRIGGEROID)
                    ereport(ERROR,
                            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                             errmsg("trigger functions can only be called as triggers")));
                else
                    ereport(ERROR,
                            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                             errmsg("PL/Tcl functions cannot return type %s",
                                    format_type_be(procStruct->prorettype))));
            }

            fmgr_info_cxt(typeStruct->typinput,
                          &(prodesc->result_in_func),
                          proc_cxt);
            prodesc->result_typioparam = getTypeIOParam(typeTup);

            prodesc->fn_retisset = procStruct->proretset;
            prodesc->fn_retistuple = (procStruct->prorettype == RECORDOID ||
                                      typeStruct->typtype == TYPTYPE_COMPOSITE);

            ReleaseSysCache(typeTup);
        }

        /************************************************************
         * Get the required information for output conversion
         * of all procedure arguments, and set up argument naming info.
         ************************************************************/
        if (!is_trigger && !is_event_trigger)
        {
            proc_internal_args[0] = '\0';
            for (i = 0; i < prodesc->nargs; i++)
            {
                typeTup = SearchSysCache1(TYPEOID,
                                          ObjectIdGetDatum(procStruct->proargtypes.values[i]));
                if (!HeapTupleIsValid(typeTup))
                    elog(ERROR, "cache lookup failed for type %u",
                         procStruct->proargtypes.values[i]);
                typeStruct = (Form_pg_type) GETSTRUCT(typeTup);

                /* Disallow pseudotype argument */
                if (typeStruct->typtype == TYPTYPE_PSEUDO)
                    ereport(ERROR,
                            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                             errmsg("PL/Tcl functions cannot accept type %s",
                                    format_type_be(procStruct->proargtypes.values[i]))));

                if (typeStruct->typtype == TYPTYPE_COMPOSITE)
                {
                    prodesc->arg_is_rowtype[i] = true;
                    snprintf(buf, sizeof(buf), "__PLTcl_Tup_%d", i + 1);
                }
                else
                {
                    prodesc->arg_is_rowtype[i] = false;
                    fmgr_info_cxt(typeStruct->typoutput,
                                  &(prodesc->arg_out_func[i]),
                                  proc_cxt);
                    snprintf(buf, sizeof(buf), "%d", i + 1);
                }

                if (i > 0)
                    strcat(proc_internal_args, " ");
                strcat(proc_internal_args, buf);

                ReleaseSysCache(typeTup);
            }
        }
        else if (is_trigger)
        {
            /* trigger procedure has fixed args */
            strcpy(proc_internal_args,
                   "TG_name TG_relid TG_table_name TG_table_schema TG_relatts TG_when TG_level TG_op __PLTcl_Tup_NEW __PLTcl_Tup_OLD args");
        }
        else if (is_event_trigger)
        {
            /* event trigger procedure has fixed args */
            strcpy(proc_internal_args, "TG_event TG_tag");
        }

        /************************************************************
         * Create the tcl command to define the internal
         * procedure
         *
         * Leave this code as DString - performance is not critical here,
         * and we don't want to duplicate the knowledge of the Tcl quoting
         * rules that's embedded in Tcl_DStringAppendElement.
         ************************************************************/
        Tcl_DStringAppendElement(&proc_internal_def, "proc");
        Tcl_DStringAppendElement(&proc_internal_def, internal_proname);
        Tcl_DStringAppendElement(&proc_internal_def, proc_internal_args);

        /************************************************************
         * prefix procedure body with
         * upvar #0 <internal_procname> GD
         * and with appropriate setting of arguments
         ************************************************************/
        Tcl_DStringAppend(&proc_internal_body, "upvar #0 ", -1);
        Tcl_DStringAppend(&proc_internal_body, internal_proname, -1);
        Tcl_DStringAppend(&proc_internal_body, " GD\n", -1);
        if (is_trigger)
        {
            Tcl_DStringAppend(&proc_internal_body,
                              "array set NEW $__PLTcl_Tup_NEW\n", -1);
            Tcl_DStringAppend(&proc_internal_body,
                              "array set OLD $__PLTcl_Tup_OLD\n", -1);
            Tcl_DStringAppend(&proc_internal_body,
                              "set i 0\n"
                              "set v 0\n"
                              "foreach v $args {\n"
                              "  incr i\n"
                              "  set $i $v\n"
                              "}\n"
                              "unset i v\n\n", -1);
        }
        else if (is_event_trigger)
        {
            /* no argument support for event triggers */
        }
        else
        {
            for (i = 0; i < prodesc->nargs; i++)
            {
                if (prodesc->arg_is_rowtype[i])
                {
                    snprintf(buf, sizeof(buf),
                             "array set %d $__PLTcl_Tup_%d\n",
                             i + 1, i + 1);
                    Tcl_DStringAppend(&proc_internal_body, buf, -1);
                }
            }
        }

        /************************************************************
         * Add user's function definition to proc body
         ************************************************************/
        prosrcdatum = SysCacheGetAttr(PROCOID, procTup,
                                      Anum_pg_proc_prosrc, &isnull);
        if (isnull)
            elog(ERROR, "null prosrc");
        proc_source = TextDatumGetCString(prosrcdatum);
        UTF_BEGIN;
        Tcl_DStringAppend(&proc_internal_body, UTF_E2U(proc_source), -1);
        UTF_END;
        pfree(proc_source);
        Tcl_DStringAppendElement(&proc_internal_def,
                                 Tcl_DStringValue(&proc_internal_body));

        /************************************************************
         * Create the procedure in the interpreter
         ************************************************************/
        tcl_rc = Tcl_EvalEx(interp,
                            Tcl_DStringValue(&proc_internal_def),
                            Tcl_DStringLength(&proc_internal_def),
                            TCL_EVAL_GLOBAL);
        if (tcl_rc != TCL_OK)
            ereport(ERROR,
                    (errcode(ERRCODE_EXTERNAL_ROUTINE_EXCEPTION),
                     errmsg("could not create internal procedure \"%s\": %s",
                            internal_proname,
                            utf_u2e(Tcl_GetStringResult(interp)))));
    }
    PG_CATCH();
    {
        /*
         * If we failed anywhere above, clean up whatever got allocated.  It
         * should all be in the proc_cxt, except for the DStrings.
         */
        if (proc_cxt)
            MemoryContextDelete(proc_cxt);
        Tcl_DStringFree(&proc_internal_def);
        Tcl_DStringFree(&proc_internal_body);
        PG_RE_THROW();
    }
    PG_END_TRY();

    /*
     * Install the new proc description block in the hashtable, incrementing
     * its refcount (the hashtable link counts as a reference).  Then, if
     * there was a previous definition of the function, decrement that one's
     * refcount, and delete it if no longer referenced.  The order of
     * operations here is important: if something goes wrong during the
     * MemoryContextDelete, leaking some memory for the old definition is OK,
     * but we don't want to corrupt the live hashtable entry.  (Likewise,
     * freeing the DStrings is pretty low priority if that happens.)
     */
    old_prodesc = proc_ptr->proc_ptr;

    proc_ptr->proc_ptr = prodesc;
    prodesc->fn_refcount++;

    if (old_prodesc != NULL)
    {
        Assert(old_prodesc->fn_refcount > 0);
        if (--old_prodesc->fn_refcount == 0)
            MemoryContextDelete(old_prodesc->fn_cxt);
    }

    Tcl_DStringFree(&proc_internal_def);
    Tcl_DStringFree(&proc_internal_body);

    ReleaseSysCache(procTup);

    return prodesc;
}


/**********************************************************************
 * pltcl_elog()     - elog() support for PLTcl
 **********************************************************************/
static int
pltcl_elog(ClientData cdata, Tcl_Interp *interp,
           int objc, Tcl_Obj *const objv[])
{
    volatile int level;
    MemoryContext oldcontext;
    int         priIndex;

    static const char *logpriorities[] = {
        "DEBUG", "LOG", "INFO", "NOTICE",
        "WARNING", "ERROR", "FATAL", (const char *) NULL
    };

    static const int loglevels[] = {
        DEBUG2, LOG, INFO, NOTICE,
        WARNING, ERROR, FATAL
    };

    if (objc != 3)
    {
        Tcl_WrongNumArgs(interp, 1, objv, "level msg");
        return TCL_ERROR;
    }

    if (Tcl_GetIndexFromObj(interp, objv[1], logpriorities, "priority",
                            TCL_EXACT, &priIndex) != TCL_OK)
        return TCL_ERROR;

    level = loglevels[priIndex];

    if (level == ERROR)
    {
        /*
         * We just pass the error back to Tcl.  If it's not caught, it'll
         * eventually get converted to a PG error when we reach the call
         * handler.
         */
        Tcl_SetObjResult(interp, objv[2]);
        return TCL_ERROR;
    }

    /*
     * For non-error messages, just pass 'em to ereport().  We do not expect
     * that this will fail, but just on the off chance it does, report the
     * error back to Tcl.  Note we are assuming that ereport() can't have any
     * internal failures that are so bad as to require a transaction abort.
     *
     * This path is also used for FATAL errors, which aren't going to come
     * back to us at all.
     */
    oldcontext = CurrentMemoryContext;
    PG_TRY();
    {
        UTF_BEGIN;
        ereport(level,
                (errcode(ERRCODE_EXTERNAL_ROUTINE_EXCEPTION),
                 errmsg("%s", UTF_U2E(Tcl_GetString(objv[2])))));
        UTF_END;
    }
    PG_CATCH();
    {
        ErrorData  *edata;

        /* Must reset elog.c's state */
        MemoryContextSwitchTo(oldcontext);
        edata = CopyErrorData();
        FlushErrorState();

        /* Pass the error data to Tcl */
        pltcl_construct_errorCode(interp, edata);
        UTF_BEGIN;
        Tcl_SetObjResult(interp, Tcl_NewStringObj(UTF_E2U(edata->message), -1));
        UTF_END;
        FreeErrorData(edata);

        return TCL_ERROR;
    }
    PG_END_TRY();

    return TCL_OK;
}


/**********************************************************************
 * pltcl_construct_errorCode()      - construct a Tcl errorCode
 *      list with detailed information from the PostgreSQL server
 **********************************************************************/
static void
pltcl_construct_errorCode(Tcl_Interp *interp, ErrorData *edata)
{
    Tcl_Obj    *obj = Tcl_NewObj();

    Tcl_ListObjAppendElement(interp, obj,
                             Tcl_NewStringObj("POSTGRES", -1));
    Tcl_ListObjAppendElement(interp, obj,
                             Tcl_NewStringObj(PG_VERSION, -1));
    Tcl_ListObjAppendElement(interp, obj,
                             Tcl_NewStringObj("SQLSTATE", -1));
    Tcl_ListObjAppendElement(interp, obj,
                             Tcl_NewStringObj(unpack_sql_state(edata->sqlerrcode), -1));
    Tcl_ListObjAppendElement(interp, obj,
                             Tcl_NewStringObj("condition", -1));
    Tcl_ListObjAppendElement(interp, obj,
                             Tcl_NewStringObj(pltcl_get_condition_name(edata->sqlerrcode), -1));
    Tcl_ListObjAppendElement(interp, obj,
                             Tcl_NewStringObj("message", -1));
    UTF_BEGIN;
    Tcl_ListObjAppendElement(interp, obj,
                             Tcl_NewStringObj(UTF_E2U(edata->message), -1));
    UTF_END;
    if (edata->detail)
    {
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj("detail", -1));
        UTF_BEGIN;
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj(UTF_E2U(edata->detail), -1));
        UTF_END;
    }
    if (edata->hint)
    {
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj("hint", -1));
        UTF_BEGIN;
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj(UTF_E2U(edata->hint), -1));
        UTF_END;
    }
    if (edata->context)
    {
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj("context", -1));
        UTF_BEGIN;
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj(UTF_E2U(edata->context), -1));
        UTF_END;
    }
    if (edata->schema_name)
    {
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj("schema", -1));
        UTF_BEGIN;
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj(UTF_E2U(edata->schema_name), -1));
        UTF_END;
    }
    if (edata->table_name)
    {
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj("table", -1));
        UTF_BEGIN;
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj(UTF_E2U(edata->table_name), -1));
        UTF_END;
    }
    if (edata->column_name)
    {
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj("column", -1));
        UTF_BEGIN;
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj(UTF_E2U(edata->column_name), -1));
        UTF_END;
    }
    if (edata->datatype_name)
    {
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj("datatype", -1));
        UTF_BEGIN;
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj(UTF_E2U(edata->datatype_name), -1));
        UTF_END;
    }
    if (edata->constraint_name)
    {
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj("constraint", -1));
        UTF_BEGIN;
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj(UTF_E2U(edata->constraint_name), -1));
        UTF_END;
    }
    /* cursorpos is never interesting here; report internal query/pos */
    if (edata->internalquery)
    {
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj("statement", -1));
        UTF_BEGIN;
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj(UTF_E2U(edata->internalquery), -1));
        UTF_END;
    }
    if (edata->internalpos > 0)
    {
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj("cursor_position", -1));
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewIntObj(edata->internalpos));
    }
    if (edata->filename)
    {
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj("filename", -1));
        UTF_BEGIN;
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj(UTF_E2U(edata->filename), -1));
        UTF_END;
    }
    if (edata->lineno > 0)
    {
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj("lineno", -1));
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewIntObj(edata->lineno));
    }
    if (edata->funcname)
    {
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj("funcname", -1));
        UTF_BEGIN;
        Tcl_ListObjAppendElement(interp, obj,
                                 Tcl_NewStringObj(UTF_E2U(edata->funcname), -1));
        UTF_END;
    }

    Tcl_SetObjErrorCode(interp, obj);
}


/**********************************************************************
 * pltcl_get_condition_name()   - find name for SQLSTATE
 **********************************************************************/
static const char *
pltcl_get_condition_name(int sqlstate)
{
    int         i;

    for (i = 0; exception_name_map[i].label != NULL; i++)
    {
        if (exception_name_map[i].sqlerrstate == sqlstate)
            return exception_name_map[i].label;
    }
    return "unrecognized_sqlstate";
}


/**********************************************************************
 * pltcl_quote()    - quote literal strings that are to
 *            be used in SPI_execute query strings
 **********************************************************************/
static int
pltcl_quote(ClientData cdata, Tcl_Interp *interp,
            int objc, Tcl_Obj *const objv[])
{
    char       *tmp;
    const char *cp1;
    char       *cp2;
    int         length;

    /************************************************************
     * Check call syntax
     ************************************************************/
    if (objc != 2)
    {
        Tcl_WrongNumArgs(interp, 1, objv, "string");
        return TCL_ERROR;
    }

    /************************************************************
     * Allocate space for the maximum the string can
     * grow to and initialize pointers
     ************************************************************/
    cp1 = Tcl_GetStringFromObj(objv[1], &length);
    tmp = palloc(length * 2 + 1);
    cp2 = tmp;

    /************************************************************
     * Walk through string and double every quote and backslash
     ************************************************************/
    while (*cp1)
    {
        if (*cp1 == '\'')
            *cp2++ = '\'';
        else
        {
            if (*cp1 == '\\')
                *cp2++ = '\\';
        }
        *cp2++ = *cp1++;
    }

    /************************************************************
     * Terminate the string and set it as result
     ************************************************************/
    *cp2 = '\0';
    Tcl_SetObjResult(interp, Tcl_NewStringObj(tmp, -1));
    pfree(tmp);
    return TCL_OK;
}


/**********************************************************************
 * pltcl_argisnull()    - determine if a specific argument is NULL
 **********************************************************************/
static int
pltcl_argisnull(ClientData cdata, Tcl_Interp *interp,
                int objc, Tcl_Obj *const objv[])
{
    int         argno;
    FunctionCallInfo fcinfo = pltcl_current_call_state->fcinfo;

    /************************************************************
     * Check call syntax
     ************************************************************/
    if (objc != 2)
    {
        Tcl_WrongNumArgs(interp, 1, objv, "argno");
        return TCL_ERROR;
    }

    /************************************************************
     * Check that we're called as a normal function
     ************************************************************/
    if (fcinfo == NULL)
    {
        Tcl_SetObjResult(interp,
                         Tcl_NewStringObj("argisnull cannot be used in triggers", -1));
        return TCL_ERROR;
    }

    /************************************************************
     * Get the argument number
     ************************************************************/
    if (Tcl_GetIntFromObj(interp, objv[1], &argno) != TCL_OK)
        return TCL_ERROR;

    /************************************************************
     * Check that the argno is valid
     ************************************************************/
    argno--;
    if (argno < 0 || argno >= fcinfo->nargs)
    {
        Tcl_SetObjResult(interp,
                         Tcl_NewStringObj("argno out of range", -1));
        return TCL_ERROR;
    }

    /************************************************************
     * Get the requested NULL state
     ************************************************************/
    Tcl_SetObjResult(interp, Tcl_NewBooleanObj(PG_ARGISNULL(argno)));
    return TCL_OK;
}


/**********************************************************************
 * pltcl_returnnull()   - Cause a NULL return from the current function
 **********************************************************************/
static int
pltcl_returnnull(ClientData cdata, Tcl_Interp *interp,
                 int objc, Tcl_Obj *const objv[])
{
    FunctionCallInfo fcinfo = pltcl_current_call_state->fcinfo;

    /************************************************************
     * Check call syntax
     ************************************************************/
    if (objc != 1)
    {
        Tcl_WrongNumArgs(interp, 1, objv, "");
        return TCL_ERROR;
    }

    /************************************************************
     * Check that we're called as a normal function
     ************************************************************/
    if (fcinfo == NULL)
    {
        Tcl_SetObjResult(interp,
                         Tcl_NewStringObj("return_null cannot be used in triggers", -1));
        return TCL_ERROR;
    }

    /************************************************************
     * Set the NULL return flag and cause Tcl to return from the
     * procedure.
     ************************************************************/
    fcinfo->isnull = true;

    return TCL_RETURN;
}


/**********************************************************************
 * pltcl_returnnext()   - Add a row to the result tuplestore in a SRF.
 **********************************************************************/
static int
pltcl_returnnext(ClientData cdata, Tcl_Interp *interp,
                 int objc, Tcl_Obj *const objv[])
{
    pltcl_call_state *call_state = pltcl_current_call_state;
    FunctionCallInfo fcinfo = call_state->fcinfo;
    pltcl_proc_desc *prodesc = call_state->prodesc;
    MemoryContext oldcontext = CurrentMemoryContext;
    ResourceOwner oldowner = CurrentResourceOwner;
    volatile int result = TCL_OK;

    /*
     * Check that we're called as a set-returning function
     */
    if (fcinfo == NULL)
    {
        Tcl_SetObjResult(interp,
                         Tcl_NewStringObj("return_next cannot be used in triggers", -1));
        return TCL_ERROR;
    }

    if (!prodesc->fn_retisset)
    {
        Tcl_SetObjResult(interp,
                         Tcl_NewStringObj("return_next cannot be used in non-set-returning functions", -1));
        return TCL_ERROR;
    }

    /*
     * Check call syntax
     */
    if (objc != 2)
    {
        Tcl_WrongNumArgs(interp, 1, objv, "result");
        return TCL_ERROR;
    }

    /*
     * The rest might throw elog(ERROR), so must run in a subtransaction.
     *
     * A small advantage of using a subtransaction is that it provides a
     * short-lived memory context for free, so we needn't worry about leaking
     * memory here.  To use that context, call BeginInternalSubTransaction
     * directly instead of going through pltcl_subtrans_begin.
     */
    BeginInternalSubTransaction(NULL);
    PG_TRY();
    {
        /* Set up tuple store if first output row */
        if (call_state->tuple_store == NULL)
            pltcl_init_tuple_store(call_state);

        if (prodesc->fn_retistuple)
        {
            Tcl_Obj   **rowObjv;
            int         rowObjc;

            /* result should be a list, so break it down */
            if (Tcl_ListObjGetElements(interp, objv[1], &rowObjc, &rowObjv) == TCL_ERROR)
                result = TCL_ERROR;
            else
            {
                HeapTuple   tuple;

                tuple = pltcl_build_tuple_result(interp, rowObjv, rowObjc,
                                                 call_state);
                tuplestore_puttuple(call_state->tuple_store, tuple);
            }
        }
        else
        {
            Datum       retval;
            bool        isNull = false;

            /* for paranoia's sake, check that tupdesc has exactly one column */
            if (call_state->ret_tupdesc->natts != 1)
                elog(ERROR, "wrong result type supplied in return_next");

            retval = InputFunctionCall(&prodesc->result_in_func,
                                       utf_u2e((char *) Tcl_GetString(objv[1])),
                                       prodesc->result_typioparam,
                                       -1);
            tuplestore_putvalues(call_state->tuple_store, call_state->ret_tupdesc,
                                 &retval, &isNull);
        }

        pltcl_subtrans_commit(oldcontext, oldowner);
    }
    PG_CATCH();
    {
        pltcl_subtrans_abort(interp, oldcontext, oldowner);
        return TCL_ERROR;
    }
    PG_END_TRY();

    return result;
}


/*----------
 * Support for running SPI operations inside subtransactions
 *
 * Intended usage pattern is:
 *
 *  MemoryContext oldcontext = CurrentMemoryContext;
 *  ResourceOwner oldowner = CurrentResourceOwner;
 *
 *  ...
 *  pltcl_subtrans_begin(oldcontext, oldowner);
 *  PG_TRY();
 *  {
 *      do something risky;
 *      pltcl_subtrans_commit(oldcontext, oldowner);
 *  }
 *  PG_CATCH();
 *  {
 *      pltcl_subtrans_abort(interp, oldcontext, oldowner);
 *      return TCL_ERROR;
 *  }
 *  PG_END_TRY();
 *  return TCL_OK;
 *----------
 */
static void
pltcl_subtrans_begin(MemoryContext oldcontext, ResourceOwner oldowner)
{
    BeginInternalSubTransaction(NULL);

    /* Want to run inside function's memory context */
    MemoryContextSwitchTo(oldcontext);
}

static void
pltcl_subtrans_commit(MemoryContext oldcontext, ResourceOwner oldowner)
{
    /* Commit the inner transaction, return to outer xact context */
    ReleaseCurrentSubTransaction();
    MemoryContextSwitchTo(oldcontext);
    CurrentResourceOwner = oldowner;
}

static void
pltcl_subtrans_abort(Tcl_Interp *interp,
                     MemoryContext oldcontext, ResourceOwner oldowner)
{
    ErrorData  *edata;

    /* Save error info */
    MemoryContextSwitchTo(oldcontext);
    edata = CopyErrorData();
    FlushErrorState();

    /* Abort the inner transaction */
    RollbackAndReleaseCurrentSubTransaction();
    MemoryContextSwitchTo(oldcontext);
    CurrentResourceOwner = oldowner;

    /* Pass the error data to Tcl */
    pltcl_construct_errorCode(interp, edata);
    UTF_BEGIN;
    Tcl_SetObjResult(interp, Tcl_NewStringObj(UTF_E2U(edata->message), -1));
    UTF_END;
    FreeErrorData(edata);
}


/**********************************************************************
 * pltcl_SPI_execute()      - The builtin SPI_execute command
 *                for the Tcl interpreter
 **********************************************************************/
static int
pltcl_SPI_execute(ClientData cdata, Tcl_Interp *interp,
                  int objc, Tcl_Obj *const objv[])
{
    int         my_rc;
    int         spi_rc;
    int         query_idx;
    int         i;
    int         optIndex;
    int         count = 0;
    const char *volatile arrayname = NULL;
    Tcl_Obj    *volatile loop_body = NULL;
    MemoryContext oldcontext = CurrentMemoryContext;
    ResourceOwner oldowner = CurrentResourceOwner;

    enum options
    {
        OPT_ARRAY, OPT_COUNT
    };

    static const char *options[] = {
        "-array", "-count", (const char *) NULL
    };

    /************************************************************
     * Check the call syntax and get the options
     ************************************************************/
    if (objc < 2)
    {
        Tcl_WrongNumArgs(interp, 1, objv,
                         "?-count n? ?-array name? query ?loop body?");
        return TCL_ERROR;
    }

    i = 1;
    while (i < objc)
    {
        if (Tcl_GetIndexFromObj(NULL, objv[i], options, NULL,
                                TCL_EXACT, &optIndex) != TCL_OK)
            break;

        if (++i >= objc)
        {
            Tcl_SetObjResult(interp,
                             Tcl_NewStringObj("missing argument to -count or -array", -1));
            return TCL_ERROR;
        }

        switch ((enum options) optIndex)
        {
            case OPT_ARRAY:
                arrayname = Tcl_GetString(objv[i++]);
                break;

            case OPT_COUNT:
                if (Tcl_GetIntFromObj(interp, objv[i++], &count) != TCL_OK)
                    return TCL_ERROR;
                break;
        }
    }

    query_idx = i;
    if (query_idx >= objc || query_idx + 2 < objc)
    {
        Tcl_WrongNumArgs(interp, query_idx - 1, objv, "query ?loop body?");
        return TCL_ERROR;
    }

    if (query_idx + 1 < objc)
        loop_body = objv[query_idx + 1];

    /************************************************************
     * Execute the query inside a sub-transaction, so we can cope with
     * errors sanely
     ************************************************************/

    pltcl_subtrans_begin(oldcontext, oldowner);

    PG_TRY();
    {
        UTF_BEGIN;
        spi_rc = SPI_execute(UTF_U2E(Tcl_GetString(objv[query_idx])),
                             pltcl_current_call_state->prodesc->fn_readonly, count);
        UTF_END;

        my_rc = pltcl_process_SPI_result(interp,
                                         arrayname,
                                         loop_body,
                                         spi_rc,
                                         SPI_tuptable,
                                         SPI_processed);

        pltcl_subtrans_commit(oldcontext, oldowner);
    }
    PG_CATCH();
    {
        pltcl_subtrans_abort(interp, oldcontext, oldowner);
        return TCL_ERROR;
    }
    PG_END_TRY();

    return my_rc;
}

/*
 * Process the result from SPI_execute or SPI_execute_plan
 *
 * Shared code between pltcl_SPI_execute and pltcl_SPI_execute_plan
 */
static int
pltcl_process_SPI_result(Tcl_Interp *interp,
                         const char *arrayname,
                         Tcl_Obj *loop_body,
                         int spi_rc,
                         SPITupleTable *tuptable,
                         uint64 ntuples)
{
    int         my_rc = TCL_OK;
    int         loop_rc;
    HeapTuple  *tuples;
    TupleDesc   tupdesc;

    switch (spi_rc)
    {
        case SPI_OK_SELINTO:
        case SPI_OK_INSERT:
        case SPI_OK_DELETE:
        case SPI_OK_UPDATE:
            Tcl_SetObjResult(interp, Tcl_NewWideIntObj(ntuples));
            break;

        case SPI_OK_UTILITY:
        case SPI_OK_REWRITTEN:
            if (tuptable == NULL)
            {
                Tcl_SetObjResult(interp, Tcl_NewIntObj(0));
                break;
            }
            /* FALL THRU for utility returning tuples */

        case SPI_OK_SELECT:
        case SPI_OK_INSERT_RETURNING:
        case SPI_OK_DELETE_RETURNING:
        case SPI_OK_UPDATE_RETURNING:

            /*
             * Process the tuples we got
             */
            tuples = tuptable->vals;
            tupdesc = tuptable->tupdesc;

            if (loop_body == NULL)
            {
                /*
                 * If there is no loop body given, just set the variables from
                 * the first tuple (if any)
                 */
                if (ntuples > 0)
                    pltcl_set_tuple_values(interp, arrayname, 0,
                                           tuples[0], tupdesc);
            }
            else
            {
                /*
                 * There is a loop body - process all tuples and evaluate the
                 * body on each
                 */
                uint64      i;

                for (i = 0; i < ntuples; i++)
                {
                    pltcl_set_tuple_values(interp, arrayname, i,
                                           tuples[i], tupdesc);

                    loop_rc = Tcl_EvalObjEx(interp, loop_body, 0);

                    if (loop_rc == TCL_OK)
                        continue;
                    if (loop_rc == TCL_CONTINUE)
                        continue;
                    if (loop_rc == TCL_RETURN)
                    {
                        my_rc = TCL_RETURN;
                        break;
                    }
                    if (loop_rc == TCL_BREAK)
                        break;
                    my_rc = TCL_ERROR;
                    break;
                }
            }

            if (my_rc == TCL_OK)
            {
                Tcl_SetObjResult(interp, Tcl_NewWideIntObj(ntuples));
            }
            break;

        default:
            Tcl_AppendResult(interp, "pltcl: SPI_execute failed: ",
                             SPI_result_code_string(spi_rc), NULL);
            my_rc = TCL_ERROR;
            break;
    }

    SPI_freetuptable(tuptable);

    return my_rc;
}


/**********************************************************************
 * pltcl_SPI_prepare()      - Builtin support for prepared plans
 *                The Tcl command SPI_prepare
 *                always saves the plan using
 *                SPI_keepplan and returns a key for
 *                access. There is no chance to prepare
 *                and not save the plan currently.
 **********************************************************************/
static int
pltcl_SPI_prepare(ClientData cdata, Tcl_Interp *interp,
                  int objc, Tcl_Obj *const objv[])
{
    volatile MemoryContext plan_cxt = NULL;
    int         nargs;
    Tcl_Obj   **argsObj;
    pltcl_query_desc *qdesc;
    int         i;
    Tcl_HashEntry *hashent;
    int         hashnew;
    Tcl_HashTable *query_hash;
    MemoryContext oldcontext = CurrentMemoryContext;
    ResourceOwner oldowner = CurrentResourceOwner;

    /************************************************************
     * Check the call syntax
     ************************************************************/
    if (objc != 3)
    {
        Tcl_WrongNumArgs(interp, 1, objv, "query argtypes");
        return TCL_ERROR;
    }

    /************************************************************
     * Split the argument type list
     ************************************************************/
    if (Tcl_ListObjGetElements(interp, objv[2], &nargs, &argsObj) != TCL_OK)
        return TCL_ERROR;

    /************************************************************
     * Allocate the new querydesc structure
     *
     * struct qdesc and subsidiary data all live in plan_cxt.  Note that if the
     * function is recompiled for whatever reason, permanent memory leaks
     * occur.  FIXME someday.
     ************************************************************/
    plan_cxt = AllocSetContextCreate(TopMemoryContext,
                                     "PL/Tcl spi_prepare query",
                                     ALLOCSET_SMALL_SIZES);
    MemoryContextSwitchTo(plan_cxt);
    qdesc = (pltcl_query_desc *) palloc0(sizeof(pltcl_query_desc));
    snprintf(qdesc->qname, sizeof(qdesc->qname), "%p", qdesc);
    qdesc->nargs = nargs;
    qdesc->argtypes = (Oid *) palloc(nargs * sizeof(Oid));
    qdesc->arginfuncs = (FmgrInfo *) palloc(nargs * sizeof(FmgrInfo));
    qdesc->argtypioparams = (Oid *) palloc(nargs * sizeof(Oid));
    MemoryContextSwitchTo(oldcontext);

    /************************************************************
     * Execute the prepare inside a sub-transaction, so we can cope with
     * errors sanely
     ************************************************************/

    pltcl_subtrans_begin(oldcontext, oldowner);

    PG_TRY();
    {
        /************************************************************
         * Resolve argument type names and then look them up by oid
         * in the system cache, and remember the required information
         * for input conversion.
         ************************************************************/
        for (i = 0; i < nargs; i++)
        {
            Oid         typId,
                        typInput,
                        typIOParam;
            int32       typmod;

            parseTypeString(Tcl_GetString(argsObj[i]), &typId, &typmod, false);

            getTypeInputInfo(typId, &typInput, &typIOParam);

            qdesc->argtypes[i] = typId;
            fmgr_info_cxt(typInput, &(qdesc->arginfuncs[i]), plan_cxt);
            qdesc->argtypioparams[i] = typIOParam;
        }

        /************************************************************
         * Prepare the plan and check for errors
         ************************************************************/
        UTF_BEGIN;
        qdesc->plan = SPI_prepare(UTF_U2E(Tcl_GetString(objv[1])),
                                  nargs, qdesc->argtypes);
        UTF_END;

        if (qdesc->plan == NULL)
            elog(ERROR, "SPI_prepare() failed");

        /************************************************************
         * Save the plan into permanent memory (right now it's in the
         * SPI procCxt, which will go away at function end).
         ************************************************************/
        if (SPI_keepplan(qdesc->plan))
            elog(ERROR, "SPI_keepplan() failed");

        pltcl_subtrans_commit(oldcontext, oldowner);
    }
    PG_CATCH();
    {
        pltcl_subtrans_abort(interp, oldcontext, oldowner);

        MemoryContextDelete(plan_cxt);

        return TCL_ERROR;
    }
    PG_END_TRY();

    /************************************************************
     * Insert a hashtable entry for the plan and return
     * the key to the caller
     ************************************************************/
    query_hash = &pltcl_current_call_state->prodesc->interp_desc->query_hash;

    hashent = Tcl_CreateHashEntry(query_hash, qdesc->qname, &hashnew);
    Tcl_SetHashValue(hashent, (ClientData) qdesc);

    /* qname is ASCII, so no need for encoding conversion */
    Tcl_SetObjResult(interp, Tcl_NewStringObj(qdesc->qname, -1));
    return TCL_OK;
}


/**********************************************************************
 * pltcl_SPI_execute_plan()     - Execute a prepared plan
 **********************************************************************/
static int
pltcl_SPI_execute_plan(ClientData cdata, Tcl_Interp *interp,
                       int objc, Tcl_Obj *const objv[])
{
    int         my_rc;
    int         spi_rc;
    int         i;
    int         j;
    int         optIndex;
    Tcl_HashEntry *hashent;
    pltcl_query_desc *qdesc;
    const char *nulls = NULL;
    const char *arrayname = NULL;
    Tcl_Obj    *loop_body = NULL;
    int         count = 0;
    int         callObjc;
    Tcl_Obj   **callObjv = NULL;
    Datum      *argvalues;
    MemoryContext oldcontext = CurrentMemoryContext;
    ResourceOwner oldowner = CurrentResourceOwner;
    Tcl_HashTable *query_hash;

    enum options
    {
        OPT_ARRAY, OPT_COUNT, OPT_NULLS
    };

    static const char *options[] = {
        "-array", "-count", "-nulls", (const char *) NULL
    };

    /************************************************************
     * Get the options and check syntax
     ************************************************************/
    i = 1;
    while (i < objc)
    {
        if (Tcl_GetIndexFromObj(NULL, objv[i], options, NULL,
                                TCL_EXACT, &optIndex) != TCL_OK)
            break;

        if (++i >= objc)
        {
            Tcl_SetObjResult(interp,
                             Tcl_NewStringObj("missing argument to -array, -count or -nulls", -1));
            return TCL_ERROR;
        }

        switch ((enum options) optIndex)
        {
            case OPT_ARRAY:
                arrayname = Tcl_GetString(objv[i++]);
                break;

            case OPT_COUNT:
                if (Tcl_GetIntFromObj(interp, objv[i++], &count) != TCL_OK)
                    return TCL_ERROR;
                break;

            case OPT_NULLS:
                nulls = Tcl_GetString(objv[i++]);
                break;
        }
    }

    /************************************************************
     * Get the prepared plan descriptor by its key
     ************************************************************/
    if (i >= objc)
    {
        Tcl_SetObjResult(interp,
                         Tcl_NewStringObj("missing argument to -count or -array", -1));
        return TCL_ERROR;
    }

    query_hash = &pltcl_current_call_state->prodesc->interp_desc->query_hash;

    hashent = Tcl_FindHashEntry(query_hash, Tcl_GetString(objv[i]));
    if (hashent == NULL)
    {
        Tcl_AppendResult(interp, "invalid queryid '", Tcl_GetString(objv[i]), "'", NULL);
        return TCL_ERROR;
    }
    qdesc = (pltcl_query_desc *) Tcl_GetHashValue(hashent);
    i++;

    /************************************************************
     * If a nulls string is given, check for correct length
     ************************************************************/
    if (nulls != NULL)
    {
        if (strlen(nulls) != qdesc->nargs)
        {
            Tcl_SetObjResult(interp,
                             Tcl_NewStringObj(
                                              "length of nulls string doesn't match number of arguments",
                                              -1));
            return TCL_ERROR;
        }
    }

    /************************************************************
     * If there was a argtype list on preparation, we need
     * an argument value list now
     ************************************************************/
    if (qdesc->nargs > 0)
    {
        if (i >= objc)
        {
            Tcl_SetObjResult(interp,
                             Tcl_NewStringObj(
                                              "argument list length doesn't match number of arguments for query"
                                              ,-1));
            return TCL_ERROR;
        }

        /************************************************************
         * Split the argument values
         ************************************************************/
        if (Tcl_ListObjGetElements(interp, objv[i++], &callObjc, &callObjv) != TCL_OK)
            return TCL_ERROR;

        /************************************************************
         * Check that the number of arguments matches
         ************************************************************/
        if (callObjc != qdesc->nargs)
        {
            Tcl_SetObjResult(interp,
                             Tcl_NewStringObj(
                                              "argument list length doesn't match number of arguments for query"
                                              ,-1));
            return TCL_ERROR;
        }
    }
    else
        callObjc = 0;

    /************************************************************
     * Get loop body if present
     ************************************************************/
    if (i < objc)
        loop_body = objv[i++];

    if (i != objc)
    {
        Tcl_WrongNumArgs(interp, 1, objv,
                         "?-count n? ?-array name? ?-nulls string? "
                         "query ?args? ?loop body?");
        return TCL_ERROR;
    }

    /************************************************************
     * Execute the plan inside a sub-transaction, so we can cope with
     * errors sanely
     ************************************************************/

    pltcl_subtrans_begin(oldcontext, oldowner);

    PG_TRY();
    {
        /************************************************************
         * Setup the value array for SPI_execute_plan() using
         * the type specific input functions
         ************************************************************/
        argvalues = (Datum *) palloc(callObjc * sizeof(Datum));

        for (j = 0; j < callObjc; j++)
        {
            if (nulls && nulls[j] == 'n')
            {
                argvalues[j] = InputFunctionCall(&qdesc->arginfuncs[j],
                                                 NULL,
                                                 qdesc->argtypioparams[j],
                                                 -1);
            }
            else
            {
                UTF_BEGIN;
                argvalues[j] = InputFunctionCall(&qdesc->arginfuncs[j],
                                                 UTF_U2E(Tcl_GetString(callObjv[j])),
                                                 qdesc->argtypioparams[j],
                                                 -1);
                UTF_END;
            }
        }

        /************************************************************
         * Execute the plan
         ************************************************************/
        spi_rc = SPI_execute_plan(qdesc->plan, argvalues, nulls,
                                  pltcl_current_call_state->prodesc->fn_readonly,
                                  count);

        my_rc = pltcl_process_SPI_result(interp,
                                         arrayname,
                                         loop_body,
                                         spi_rc,
                                         SPI_tuptable,
                                         SPI_processed);

        pltcl_subtrans_commit(oldcontext, oldowner);
    }
    PG_CATCH();
    {
        pltcl_subtrans_abort(interp, oldcontext, oldowner);
        return TCL_ERROR;
    }
    PG_END_TRY();

    return my_rc;
}


/**********************************************************************
 * pltcl_SPI_lastoid()  - return the last oid. To
 *        be used after insert queries
 **********************************************************************/
static int
pltcl_SPI_lastoid(ClientData cdata, Tcl_Interp *interp,
                  int objc, Tcl_Obj *const objv[])
{
    /*
     * Check call syntax
     */
    if (objc != 1)
    {
        Tcl_WrongNumArgs(interp, 1, objv, "");
        return TCL_ERROR;
    }

    Tcl_SetObjResult(interp, Tcl_NewWideIntObj(SPI_lastoid));
    return TCL_OK;
}


/**********************************************************************
 * pltcl_subtransaction()   - Execute some Tcl code in a subtransaction
 *
 * The subtransaction is aborted if the Tcl code fragment returns TCL_ERROR,
 * otherwise it's subcommitted.
 **********************************************************************/
static int
pltcl_subtransaction(ClientData cdata, Tcl_Interp *interp,
                     int objc, Tcl_Obj *const objv[])
{
    MemoryContext oldcontext = CurrentMemoryContext;
    ResourceOwner oldowner = CurrentResourceOwner;
    int         retcode;

    if (objc != 2)
    {
        Tcl_WrongNumArgs(interp, 1, objv, "command");
        return TCL_ERROR;
    }

    /*
     * Note: we don't use pltcl_subtrans_begin and friends here because we
     * don't want the error handling in pltcl_subtrans_abort.  But otherwise
     * the processing should be about the same as in those functions.
     */
    BeginInternalSubTransaction(NULL);
    MemoryContextSwitchTo(oldcontext);

    retcode = Tcl_EvalObjEx(interp, objv[1], 0);

    if (retcode == TCL_ERROR)
    {
        /* Rollback the subtransaction */
        RollbackAndReleaseCurrentSubTransaction();
    }
    else
    {
        /* Commit the subtransaction */
        ReleaseCurrentSubTransaction();
    }

    /* In either case, restore previous memory context and resource owner */
    MemoryContextSwitchTo(oldcontext);
    CurrentResourceOwner = oldowner;

    return retcode;
}


/**********************************************************************
 * pltcl_set_tuple_values() - Set variables for all attributes
 *                of a given tuple
 *
 * Note: arrayname is presumed to be UTF8; it usually came from Tcl
 **********************************************************************/
static void
pltcl_set_tuple_values(Tcl_Interp *interp, const char *arrayname,
                       uint64 tupno, HeapTuple tuple, TupleDesc tupdesc)
{
    int         i;
    char       *outputstr;
    Datum       attr;
    bool        isnull;
    const char *attname;
    Oid         typoutput;
    bool        typisvarlena;
    const char **arrptr;
    const char **nameptr;
    const char *nullname = NULL;

    /************************************************************
     * Prepare pointers for Tcl_SetVar2() below
     ************************************************************/
    if (arrayname == NULL)
    {
        arrptr = &attname;
        nameptr = &nullname;
    }
    else
    {
        arrptr = &arrayname;
        nameptr = &attname;

        /*
         * When outputting to an array, fill the ".tupno" element with the
         * current tuple number.  This will be overridden below if ".tupno" is
         * in use as an actual field name in the rowtype.
         */
        Tcl_SetVar2Ex(interp, arrayname, ".tupno", Tcl_NewWideIntObj(tupno), 0);
    }

    for (i = 0; i < tupdesc->natts; i++)
    {
        /* ignore dropped attributes */
        if (tupdesc->attrs[i]->attisdropped)
            continue;

        /************************************************************
         * Get the attribute name
         ************************************************************/
        UTF_BEGIN;
        attname = pstrdup(UTF_E2U(NameStr(tupdesc->attrs[i]->attname)));
        UTF_END;

        /************************************************************
         * Get the attributes value
         ************************************************************/
        attr = heap_getattr(tuple, i + 1, tupdesc, &isnull);

        /************************************************************
         * If there is a value, set the variable
         * If not, unset it
         *
         * Hmmm - Null attributes will cause functions to
         *        crash if they don't expect them - need something
         *        smarter here.
         ************************************************************/
        if (!isnull)
        {
            getTypeOutputInfo(tupdesc->attrs[i]->atttypid,
                              &typoutput, &typisvarlena);
            outputstr = OidOutputFunctionCall(typoutput, attr);
            UTF_BEGIN;
            Tcl_SetVar2Ex(interp, *arrptr, *nameptr,
                          Tcl_NewStringObj(UTF_E2U(outputstr), -1), 0);
            UTF_END;
            pfree(outputstr);
        }
        else
            Tcl_UnsetVar2(interp, *arrptr, *nameptr, 0);

        pfree((char *) attname);
    }
}


/**********************************************************************
 * pltcl_build_tuple_argument() - Build a list object usable for 'array set'
 *                from all attributes of a given tuple
 **********************************************************************/
static Tcl_Obj *
pltcl_build_tuple_argument(HeapTuple tuple, TupleDesc tupdesc)
{
    Tcl_Obj    *retobj = Tcl_NewObj();
    int         i;
    char       *outputstr;
    Datum       attr;
    bool        isnull;
    char       *attname;
    Oid         typoutput;
    bool        typisvarlena;

    for (i = 0; i < tupdesc->natts; i++)
    {
        /* ignore dropped attributes */
        if (tupdesc->attrs[i]->attisdropped)
            continue;

        /************************************************************
         * Get the attribute name
         ************************************************************/
        attname = NameStr(tupdesc->attrs[i]->attname);

        /************************************************************
         * Get the attributes value
         ************************************************************/
        attr = heap_getattr(tuple, i + 1, tupdesc, &isnull);

        /************************************************************
         * If there is a value, append the attribute name and the
         * value to the list
         *
         * Hmmm - Null attributes will cause functions to
         *        crash if they don't expect them - need something
         *        smarter here.
         ************************************************************/
        if (!isnull)
        {
            getTypeOutputInfo(tupdesc->attrs[i]->atttypid,
                              &typoutput, &typisvarlena);
            outputstr = OidOutputFunctionCall(typoutput, attr);
            UTF_BEGIN;
            Tcl_ListObjAppendElement(NULL, retobj,
                                     Tcl_NewStringObj(UTF_E2U(attname), -1));
            UTF_END;
            UTF_BEGIN;
            Tcl_ListObjAppendElement(NULL, retobj,
                                     Tcl_NewStringObj(UTF_E2U(outputstr), -1));
            UTF_END;
            pfree(outputstr);
        }
    }

    return retobj;
}

/**********************************************************************
 * pltcl_build_tuple_result() - Build a tuple of function's result rowtype
 *                from a Tcl list of column names and values
 *
 * In a trigger function, we build a tuple of the trigger table's rowtype.
 *
 * Note: this function leaks memory.  Even if we made it clean up its own
 * mess, there's no way to prevent the datatype input functions it calls
 * from leaking.  Run it in a short-lived context, unless we're about to
 * exit the procedure anyway.
 **********************************************************************/
static HeapTuple
pltcl_build_tuple_result(Tcl_Interp *interp, Tcl_Obj **kvObjv, int kvObjc,
                         pltcl_call_state *call_state)
{
    TupleDesc   tupdesc;
    AttInMetadata *attinmeta;
    char      **values;
    int         i;

    if (call_state->ret_tupdesc)
    {
        tupdesc = call_state->ret_tupdesc;
        attinmeta = call_state->attinmeta;
    }
    else if (call_state->trigdata)
    {
        tupdesc = RelationGetDescr(call_state->trigdata->tg_relation);
        attinmeta = TupleDescGetAttInMetadata(tupdesc);
    }
    else
    {
        elog(ERROR, "PL/Tcl function does not return a tuple");
        tupdesc = NULL;         /* keep compiler quiet */
        attinmeta = NULL;
    }

    values = (char **) palloc0(tupdesc->natts * sizeof(char *));

    if (kvObjc % 2 != 0)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("column name/value list must have even number of elements")));

    for (i = 0; i < kvObjc; i += 2)
    {
        char       *fieldName = utf_u2e(Tcl_GetString(kvObjv[i]));
        int         attn = SPI_fnumber(tupdesc, fieldName);

        /*
         * We silently ignore ".tupno", if it's present but doesn't match any
         * actual output column.  This allows direct use of a row returned by
         * pltcl_set_tuple_values().
         */
        if (attn == SPI_ERROR_NOATTRIBUTE)
        {
            if (strcmp(fieldName, ".tupno") == 0)
                continue;
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_COLUMN),
                     errmsg("column name/value list contains nonexistent column name \"%s\"",
                            fieldName)));
        }

        if (attn <= 0)
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("cannot set system attribute \"%s\"",
                            fieldName)));

        values[attn - 1] = utf_u2e(Tcl_GetString(kvObjv[i + 1]));
    }

    return BuildTupleFromCStrings(attinmeta, values);
}

/**********************************************************************
 * pltcl_init_tuple_store() - Initialize the result tuplestore for a SRF
 **********************************************************************/
static void
pltcl_init_tuple_store(pltcl_call_state *call_state)
{
    ReturnSetInfo *rsi = call_state->rsi;
    MemoryContext oldcxt;
    ResourceOwner oldowner;

    /* Should be in a SRF */
    Assert(rsi);
    /* Should be first time through */
    Assert(!call_state->tuple_store);
    Assert(!call_state->attinmeta);

    /* We expect caller to provide an appropriate result tupdesc */
    Assert(rsi->expectedDesc);
    call_state->ret_tupdesc = rsi->expectedDesc;

    /*
     * Switch to the right memory context and resource owner for storing the
     * tuplestore. If we're within a subtransaction opened for an exception
     * block, for example, we must still create the tuplestore in the resource
     * owner that was active when this function was entered, and not in the
     * subtransaction's resource owner.
     */
    oldcxt = MemoryContextSwitchTo(call_state->tuple_store_cxt);
    oldowner = CurrentResourceOwner;
    CurrentResourceOwner = call_state->tuple_store_owner;

    call_state->tuple_store =
        tuplestore_begin_heap(rsi->allowedModes & SFRM_Materialize_Random,
                              false, work_mem);

    /* Build attinmeta in this context, too */
    call_state->attinmeta = TupleDescGetAttInMetadata(call_state->ret_tupdesc);

    CurrentResourceOwner = oldowner;
    MemoryContextSwitchTo(oldcxt);
}