fastpath.c

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/*-------------------------------------------------------------------------
 *
 * fastpath.c
 *    routines to handle function requests from the frontend
 *
 * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/tcop/fastpath.c
 *
 * NOTES
 *    This cruft is the server side of PQfn.
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/htup_details.h"
#include "access/xact.h"
#include "catalog/objectaccess.h"
#include "catalog/pg_proc.h"
#include "libpq/libpq.h"
#include "libpq/pqformat.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "port/pg_bswap.h"
#include "tcop/fastpath.h"
#include "tcop/tcopprot.h"
#include "utils/acl.h"
#include "utils/lsyscache.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"


/*
 * Formerly, this code attempted to cache the function and type info
 * looked up by fetch_fp_info, but only for the duration of a single
 * transaction command (since in theory the info could change between
 * commands).  This was utterly useless, because postgres.c executes
 * each fastpath call as a separate transaction command, and so the
 * cached data could never actually have been reused.  If it had worked
 * as intended, it would have had problems anyway with dangling references
 * in the FmgrInfo struct.  So, forget about caching and just repeat the
 * syscache fetches on each usage.  They're not *that* expensive.
 */
struct fp_info
{
    Oid         funcid;
    FmgrInfo    flinfo;         /* function lookup info for funcid */
    Oid         namespace;      /* other stuff from pg_proc */
    Oid         rettype;
    Oid         argtypes[FUNC_MAX_ARGS];
    char        fname[NAMEDATALEN]; /* function name for logging */
};


static int16 parse_fcall_arguments(StringInfo msgBuf, struct fp_info *fip,
                                   FunctionCallInfo fcinfo);

/* ----------------
 *      SendFunctionResult
 * ----------------
 */
static void
SendFunctionResult(Datum retval, bool isnull, Oid rettype, int16 format)
{
    StringInfoData buf;

    pq_beginmessage(&buf, 'V');

    if (isnull)
    {
        pq_sendint32(&buf, -1);
    }
    else
    {
        if (format == 0)
        {
            Oid         typoutput;
            bool        typisvarlena;
            char       *outputstr;

            getTypeOutputInfo(rettype, &typoutput, &typisvarlena);
            outputstr = OidOutputFunctionCall(typoutput, retval);
            pq_sendcountedtext(&buf, outputstr, strlen(outputstr), false);
            pfree(outputstr);
        }
        else if (format == 1)
        {
            Oid         typsend;
            bool        typisvarlena;
            bytea      *outputbytes;

            getTypeBinaryOutputInfo(rettype, &typsend, &typisvarlena);
            outputbytes = OidSendFunctionCall(typsend, retval);
            pq_sendint32(&buf, VARSIZE(outputbytes) - VARHDRSZ);
            pq_sendbytes(&buf, VARDATA(outputbytes),
                         VARSIZE(outputbytes) - VARHDRSZ);
            pfree(outputbytes);
        }
        else
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("unsupported format code: %d", format)));
    }

    pq_endmessage(&buf);
}

/*
 * fetch_fp_info
 *
 * Performs catalog lookups to load a struct fp_info 'fip' for the
 * function 'func_id'.
 */
static void
fetch_fp_info(Oid func_id, struct fp_info *fip)
{
    HeapTuple   func_htp;
    Form_pg_proc pp;

    Assert(fip != NULL);

    /*
     * Since the validity of this structure is determined by whether the
     * funcid is OK, we clear the funcid here.  It must not be set to the
     * correct value until we are about to return with a good struct fp_info,
     * since we can be interrupted (i.e., with an ereport(ERROR, ...)) at any
     * time.  [No longer really an issue since we don't save the struct
     * fp_info across transactions anymore, but keep it anyway.]
     */
    MemSet(fip, 0, sizeof(struct fp_info));
    fip->funcid = InvalidOid;

    func_htp = SearchSysCache1(PROCOID, ObjectIdGetDatum(func_id));
    if (!HeapTupleIsValid(func_htp))
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_FUNCTION),
                 errmsg("function with OID %u does not exist", func_id)));
    pp = (Form_pg_proc) GETSTRUCT(func_htp);

    /* reject pg_proc entries that are unsafe to call via fastpath */
    if (pp->prokind != PROKIND_FUNCTION || pp->proretset)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("cannot call function %s via fastpath interface",
                        NameStr(pp->proname))));

    /* watch out for catalog entries with more than FUNC_MAX_ARGS args */
    if (pp->pronargs > FUNC_MAX_ARGS)
        elog(ERROR, "function %s has more than %d arguments",
             NameStr(pp->proname), FUNC_MAX_ARGS);

    fip->namespace = pp->pronamespace;
    fip->rettype = pp->prorettype;
    memcpy(fip->argtypes, pp->proargtypes.values, pp->pronargs * sizeof(Oid));
    strlcpy(fip->fname, NameStr(pp->proname), NAMEDATALEN);

    ReleaseSysCache(func_htp);

    fmgr_info(func_id, &fip->flinfo);

    /*
     * This must be last!
     */
    fip->funcid = func_id;
}


/*
 * HandleFunctionRequest
 *
 * Server side of PQfn (fastpath function calls from the frontend).
 * This corresponds to the libpq protocol symbol "F".
 *
 * INPUT:
 *      postgres.c has already read the message body and will pass it in
 *      msgBuf.
 *
 * Note: palloc()s done here and in the called function do not need to be
 * cleaned up explicitly.  We are called from PostgresMain() in the
 * MessageContext memory context, which will be automatically reset when
 * control returns to PostgresMain.
 */
void
HandleFunctionRequest(StringInfo msgBuf)
{
    LOCAL_FCINFO(fcinfo, FUNC_MAX_ARGS);
    Oid         fid;
    AclResult   aclresult;
    int16       rformat;
    Datum       retval;
    struct fp_info my_fp;
    struct fp_info *fip;
    bool        callit;
    bool        was_logged = false;
    char        msec_str[32];

    /*
     * We only accept COMMIT/ABORT if we are in an aborted transaction, and
     * COMMIT/ABORT cannot be executed through the fastpath interface.
     */
    if (IsAbortedTransactionBlockState())
        ereport(ERROR,
                (errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
                 errmsg("current transaction is aborted, "
                        "commands ignored until end of transaction block")));

    /*
     * Now that we know we are in a valid transaction, set snapshot in case
     * needed by function itself or one of the datatype I/O routines.
     */
    PushActiveSnapshot(GetTransactionSnapshot());

    /*
     * Begin parsing the buffer contents.
     */
    fid = (Oid) pq_getmsgint(msgBuf, 4);    /* function oid */

    /*
     * There used to be a lame attempt at caching lookup info here. Now we
     * just do the lookups on every call.
     */
    fip = &my_fp;
    fetch_fp_info(fid, fip);

    /* Log as soon as we have the function OID and name */
    if (log_statement == LOGSTMT_ALL)
    {
        ereport(LOG,
                (errmsg("fastpath function call: \"%s\" (OID %u)",
                        fip->fname, fid)));
        was_logged = true;
    }

    /*
     * Check permission to access and call function.  Since we didn't go
     * through a normal name lookup, we need to check schema usage too.
     */
    aclresult = pg_namespace_aclcheck(fip->namespace, GetUserId(), ACL_USAGE);
    if (aclresult != ACLCHECK_OK)
        aclcheck_error(aclresult, OBJECT_SCHEMA,
                       get_namespace_name(fip->namespace));
    InvokeNamespaceSearchHook(fip->namespace, true);

    aclresult = pg_proc_aclcheck(fid, GetUserId(), ACL_EXECUTE);
    if (aclresult != ACLCHECK_OK)
        aclcheck_error(aclresult, OBJECT_FUNCTION,
                       get_func_name(fid));
    InvokeFunctionExecuteHook(fid);

    /*
     * Prepare function call info block and insert arguments.
     *
     * Note: for now we pass collation = InvalidOid, so collation-sensitive
     * functions can't be called this way.  Perhaps we should pass
     * DEFAULT_COLLATION_OID, instead?
     */
    InitFunctionCallInfoData(*fcinfo, &fip->flinfo, 0, InvalidOid, NULL, NULL);

    rformat = parse_fcall_arguments(msgBuf, fip, fcinfo);

    /* Verify we reached the end of the message where expected. */
    pq_getmsgend(msgBuf);

    /*
     * If func is strict, must not call it for null args.
     */
    callit = true;
    if (fip->flinfo.fn_strict)
    {
        int         i;

        for (i = 0; i < fcinfo->nargs; i++)
        {
            if (fcinfo->args[i].isnull)
            {
                callit = false;
                break;
            }
        }
    }

    if (callit)
    {
        /* Okay, do it ... */
        retval = FunctionCallInvoke(fcinfo);
    }
    else
    {
        fcinfo->isnull = true;
        retval = (Datum) 0;
    }

    /* ensure we do at least one CHECK_FOR_INTERRUPTS per function call */
    CHECK_FOR_INTERRUPTS();

    SendFunctionResult(retval, fcinfo->isnull, fip->rettype, rformat);

    /* We no longer need the snapshot */
    PopActiveSnapshot();

    /*
     * Emit duration logging if appropriate.
     */
    switch (check_log_duration(msec_str, was_logged))
    {
        case 1:
            ereport(LOG,
                    (errmsg("duration: %s ms", msec_str)));
            break;
        case 2:
            ereport(LOG,
                    (errmsg("duration: %s ms  fastpath function call: \"%s\" (OID %u)",
                            msec_str, fip->fname, fid)));
            break;
    }
}

/*
 * Parse function arguments in a 3.0 protocol message
 *
 * Argument values are loaded into *fcinfo, and the desired result format
 * is returned.
 */
static int16
parse_fcall_arguments(StringInfo msgBuf, struct fp_info *fip,
                      FunctionCallInfo fcinfo)
{
    int         nargs;
    int         i;
    int         numAFormats;
    int16      *aformats = NULL;
    StringInfoData abuf;

    /* Get the argument format codes */
    numAFormats = pq_getmsgint(msgBuf, 2);
    if (numAFormats > 0)
    {
        aformats = (int16 *) palloc(numAFormats * sizeof(int16));
        for (i = 0; i < numAFormats; i++)
            aformats[i] = pq_getmsgint(msgBuf, 2);
    }

    nargs = pq_getmsgint(msgBuf, 2);    /* # of arguments */

    if (fip->flinfo.fn_nargs != nargs || nargs > FUNC_MAX_ARGS)
        ereport(ERROR,
                (errcode(ERRCODE_PROTOCOL_VIOLATION),
                 errmsg("function call message contains %d arguments but function requires %d",
                        nargs, fip->flinfo.fn_nargs)));

    fcinfo->nargs = nargs;

    if (numAFormats > 1 && numAFormats != nargs)
        ereport(ERROR,
                (errcode(ERRCODE_PROTOCOL_VIOLATION),
                 errmsg("function call message contains %d argument formats but %d arguments",
                        numAFormats, nargs)));

    initStringInfo(&abuf);

    /*
     * Copy supplied arguments into arg vector.
     */
    for (i = 0; i < nargs; ++i)
    {
        int         argsize;
        int16       aformat;

        argsize = pq_getmsgint(msgBuf, 4);
        if (argsize == -1)
        {
            fcinfo->args[i].isnull = true;
        }
        else
        {
            fcinfo->args[i].isnull = false;
            if (argsize < 0)
                ereport(ERROR,
                        (errcode(ERRCODE_PROTOCOL_VIOLATION),
                         errmsg("invalid argument size %d in function call message",
                                argsize)));

            /* Reset abuf to empty, and insert raw data into it */
            resetStringInfo(&abuf);
            appendBinaryStringInfo(&abuf,
                                   pq_getmsgbytes(msgBuf, argsize),
                                   argsize);
        }

        if (numAFormats > 1)
            aformat = aformats[i];
        else if (numAFormats > 0)
            aformat = aformats[0];
        else
            aformat = 0;        /* default = text */

        if (aformat == 0)
        {
            Oid         typinput;
            Oid         typioparam;
            char       *pstring;

            getTypeInputInfo(fip->argtypes[i], &typinput, &typioparam);

            /*
             * Since stringinfo.c keeps a trailing null in place even for
             * binary data, the contents of abuf are a valid C string.  We
             * have to do encoding conversion before calling the typinput
             * routine, though.
             */
            if (argsize == -1)
                pstring = NULL;
            else
                pstring = pg_client_to_server(abuf.data, argsize);

            fcinfo->args[i].value = OidInputFunctionCall(typinput, pstring,
                                                         typioparam, -1);
            /* Free result of encoding conversion, if any */
            if (pstring && pstring != abuf.data)
                pfree(pstring);
        }
        else if (aformat == 1)
        {
            Oid         typreceive;
            Oid         typioparam;
            StringInfo  bufptr;

            /* Call the argument type's binary input converter */
            getTypeBinaryInputInfo(fip->argtypes[i], &typreceive, &typioparam);

            if (argsize == -1)
                bufptr = NULL;
            else
                bufptr = &abuf;

            fcinfo->args[i].value = OidReceiveFunctionCall(typreceive, bufptr,
                                                           typioparam, -1);

            /* Trouble if it didn't eat the whole buffer */
            if (argsize != -1 && abuf.cursor != abuf.len)
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_BINARY_REPRESENTATION),
                         errmsg("incorrect binary data format in function argument %d",
                                i + 1)));
        }
        else
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("unsupported format code: %d", aformat)));
    }

    /* Return result format code */
    return (int16) pq_getmsgint(msgBuf, 2);
}