fmgr.h

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/*-------------------------------------------------------------------------
 *
 * fmgr.h
 *    Definitions for the Postgres function manager and function-call
 *    interface.
 *
 * This file must be included by all Postgres modules that either define
 * or call fmgr-callable functions.
 *
 *
 * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/fmgr.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef FMGR_H
#define FMGR_H
 
/* We don't want to include primnodes.h here, so make some stub references */
typedef struct Node *fmNodePtr;
typedef struct Aggref *fmAggrefPtr;
 
/* Likewise, avoid including execnodes.h here */
typedef void (*fmExprContextCallbackFunction) (Datum arg);
 
/* Likewise, avoid including stringinfo.h here */
typedef struct StringInfoData *fmStringInfo;
 
 
/*
 * All functions that can be called directly by fmgr must have this signature.
 * (Other functions can be called by using a handler that does have this
 * signature.)
 */
 
typedef struct FunctionCallInfoBaseData *FunctionCallInfo;
 
typedef Datum (*PGFunction) (FunctionCallInfo fcinfo);
 
/*
 * This struct holds the system-catalog information that must be looked up
 * before a function can be called through fmgr.  If the same function is
 * to be called multiple times, the lookup need be done only once and the
 * info struct saved for re-use.
 *
 * Note that fn_expr really is parse-time-determined information about the
 * arguments, rather than about the function itself.  But it's convenient to
 * store it here rather than in FunctionCallInfoBaseData, where it might more
 * logically belong.
 *
 * fn_extra is available for use by the called function; all other fields
 * should be treated as read-only after the struct is created.
 */
typedef struct FmgrInfo
{
    PGFunction  fn_addr;        /* pointer to function or handler to be called */
    Oid         fn_oid;         /* OID of function (NOT of handler, if any) */
    short       fn_nargs;       /* number of input args (0..FUNC_MAX_ARGS) */
    bool        fn_strict;      /* function is "strict" (NULL in => NULL out) */
    bool        fn_retset;      /* function returns a set */
    unsigned char fn_stats;     /* collect stats if track_functions > this */
    void       *fn_extra;       /* extra space for use by handler */
    MemoryContext fn_mcxt;      /* memory context to store fn_extra in */
    fmNodePtr   fn_expr;        /* expression parse tree for call, or NULL */
} FmgrInfo;
 
/*
 * This struct is the data actually passed to an fmgr-called function.
 *
 * The called function is expected to set isnull, and possibly resultinfo or
 * fields in whatever resultinfo points to.  It should not change any other
 * fields.  (In particular, scribbling on the argument arrays is a bad idea,
 * since some callers assume they can re-call with the same arguments.)
 *
 * Note that enough space for arguments needs to be provided, either by using
 * SizeForFunctionCallInfo() in dynamic allocations, or by using
 * LOCAL_FCINFO() for on-stack allocations.
 *
 * This struct is named *BaseData, rather than *Data, to break pre v12 code
 * that allocated FunctionCallInfoData itself, as it'd often silently break
 * old code due to no space for arguments being provided.
 */
typedef struct FunctionCallInfoBaseData
{
    FmgrInfo   *flinfo;         /* ptr to lookup info used for this call */
    fmNodePtr   context;        /* pass info about context of call */
    fmNodePtr   resultinfo;     /* pass or return extra info about result */
    Oid         fncollation;    /* collation for function to use */
#define FIELDNO_FUNCTIONCALLINFODATA_ISNULL 4
    bool        isnull;         /* function must set true if result is NULL */
    short       nargs;          /* # arguments actually passed */
#define FIELDNO_FUNCTIONCALLINFODATA_ARGS 6
    NullableDatum args[FLEXIBLE_ARRAY_MEMBER];
} FunctionCallInfoBaseData;
 
/*
 * Space needed for a FunctionCallInfoBaseData struct with sufficient space
 * for `nargs` arguments.
 */
#define SizeForFunctionCallInfo(nargs) \
    (offsetof(FunctionCallInfoBaseData, args) + \
     sizeof(NullableDatum) * (nargs))
 
/*
 * This macro ensures that `name` points to a stack-allocated
 * FunctionCallInfoBaseData struct with sufficient space for `nargs` arguments.
 */
#define LOCAL_FCINFO(name, nargs) \
    /* use union with FunctionCallInfoBaseData to guarantee alignment */ \
    union \
    { \
        FunctionCallInfoBaseData fcinfo; \
        /* ensure enough space for nargs args is available */ \
        char fcinfo_data[SizeForFunctionCallInfo(nargs)]; \
    } name##data; \
    FunctionCallInfo name = &name##data.fcinfo
 
/*
 * This routine fills a FmgrInfo struct, given the OID
 * of the function to be called.
 */
extern void fmgr_info(Oid functionId, FmgrInfo *finfo);
 
/*
 * Same, when the FmgrInfo struct is in a memory context longer-lived than
 * CurrentMemoryContext.  The specified context will be set as fn_mcxt
 * and used to hold all subsidiary data of finfo.
 */
extern void fmgr_info_cxt(Oid functionId, FmgrInfo *finfo,
                          MemoryContext mcxt);
 
/* Convenience macro for setting the fn_expr field */
#define fmgr_info_set_expr(expr, finfo) \
    ((finfo)->fn_expr = (expr))
 
/*
 * Copy an FmgrInfo struct
 */
extern void fmgr_info_copy(FmgrInfo *dstinfo, FmgrInfo *srcinfo,
                           MemoryContext destcxt);
 
extern void fmgr_symbol(Oid functionId, char **mod, char **fn);
 
/*
 * This macro initializes all the fields of a FunctionCallInfoBaseData except
 * for the args[] array.
 */
#define InitFunctionCallInfoData(Fcinfo, Flinfo, Nargs, Collation, Context, Resultinfo) \
    do { \
        (Fcinfo).flinfo = (Flinfo); \
        (Fcinfo).context = (Context); \
        (Fcinfo).resultinfo = (Resultinfo); \
        (Fcinfo).fncollation = (Collation); \
        (Fcinfo).isnull = false; \
        (Fcinfo).nargs = (Nargs); \
    } while (0)
 
/*
 * This macro invokes a function given a filled-in FunctionCallInfoBaseData
 * struct.  The macro result is the returned Datum --- but note that
 * caller must still check fcinfo->isnull!  Also, if function is strict,
 * it is caller's responsibility to verify that no null arguments are present
 * before calling.
 *
 * Some code performs multiple calls without redoing InitFunctionCallInfoData,
 * possibly altering the argument values.  This is okay, but be sure to reset
 * the fcinfo->isnull flag before each call, since callees are permitted to
 * assume that starts out false.
 */
#define FunctionCallInvoke(fcinfo)  ((* (fcinfo)->flinfo->fn_addr) (fcinfo))
 
 
/*-------------------------------------------------------------------------
 *      Support macros to ease writing fmgr-compatible functions
 *
 * A C-coded fmgr-compatible function should be declared as
 *
 *      Datum
 *      function_name(PG_FUNCTION_ARGS)
 *      {
 *          ...
 *      }
 *
 * It should access its arguments using appropriate PG_GETARG_xxx macros
 * and should return its result using PG_RETURN_xxx.
 *
 *-------------------------------------------------------------------------
 */
 
/* Standard parameter list for fmgr-compatible functions */
#define PG_FUNCTION_ARGS    FunctionCallInfo fcinfo
 
/*
 * Get collation function should use.
 */
#define PG_GET_COLLATION()  (fcinfo->fncollation)
 
/*
 * Get number of arguments passed to function.
 */
#define PG_NARGS() (fcinfo->nargs)
 
/*
 * If function is not marked "proisstrict" in pg_proc, it must check for
 * null arguments using this macro.  Do not try to GETARG a null argument!
 */
#define PG_ARGISNULL(n)  (fcinfo->args[n].isnull)
 
/*
 * Support for fetching detoasted copies of toastable datatypes (all of
 * which are varlena types).  pg_detoast_datum() gives you either the input
 * datum (if not toasted) or a detoasted copy allocated with palloc().
 * pg_detoast_datum_copy() always gives you a palloc'd copy --- use it
 * if you need a modifiable copy of the input.  Caller is expected to have
 * checked for null inputs first, if necessary.
 *
 * pg_detoast_datum_packed() will return packed (1-byte header) datums
 * unmodified.  It will still expand an externally toasted or compressed datum.
 * The resulting datum can be accessed using VARSIZE_ANY() and VARDATA_ANY()
 * (beware of multiple evaluations in those macros!)
 *
 * In consumers oblivious to data alignment, call PG_DETOAST_DATUM_PACKED(),
 * VARDATA_ANY(), VARSIZE_ANY() and VARSIZE_ANY_EXHDR().  Elsewhere, call
 * PG_DETOAST_DATUM(), VARDATA() and VARSIZE().  Directly fetching an int16,
 * int32 or wider field in the struct representing the datum layout requires
 * aligned data.  memcpy() is alignment-oblivious, as are most operations on
 * datatypes, such as text, whose layout struct contains only char fields.
 *
 * Note: it'd be nice if these could be macros, but I see no way to do that
 * without evaluating the arguments multiple times, which is NOT acceptable.
 */
extern struct varlena *pg_detoast_datum(struct varlena *datum);
extern struct varlena *pg_detoast_datum_copy(struct varlena *datum);
extern struct varlena *pg_detoast_datum_slice(struct varlena *datum,
                                              int32 first, int32 count);
extern struct varlena *pg_detoast_datum_packed(struct varlena *datum);
 
#define PG_DETOAST_DATUM(datum) \
    pg_detoast_datum((struct varlena *) DatumGetPointer(datum))
#define PG_DETOAST_DATUM_COPY(datum) \
    pg_detoast_datum_copy((struct varlena *) DatumGetPointer(datum))
#define PG_DETOAST_DATUM_SLICE(datum,f,c) \
        pg_detoast_datum_slice((struct varlena *) DatumGetPointer(datum), \
        (int32) (f), (int32) (c))
/* WARNING -- unaligned pointer */
#define PG_DETOAST_DATUM_PACKED(datum) \
    pg_detoast_datum_packed((struct varlena *) DatumGetPointer(datum))
 
/*
 * Support for cleaning up detoasted copies of inputs.  This must only
 * be used for pass-by-ref datatypes, and normally would only be used
 * for toastable types.  If the given pointer is different from the
 * original argument, assume it's a palloc'd detoasted copy, and pfree it.
 * NOTE: most functions on toastable types do not have to worry about this,
 * but we currently require that support functions for indexes not leak
 * memory.
 */
#define PG_FREE_IF_COPY(ptr,n) \
    do { \
        if ((Pointer) (ptr) != PG_GETARG_POINTER(n)) \
            pfree(ptr); \
    } while (0)
 
/* Macros for fetching arguments of standard types */
 
#define PG_GETARG_DATUM(n)   (fcinfo->args[n].value)
#define PG_GETARG_INT32(n)   DatumGetInt32(PG_GETARG_DATUM(n))
#define PG_GETARG_UINT32(n)  DatumGetUInt32(PG_GETARG_DATUM(n))
#define PG_GETARG_INT16(n)   DatumGetInt16(PG_GETARG_DATUM(n))
#define PG_GETARG_UINT16(n)  DatumGetUInt16(PG_GETARG_DATUM(n))
#define PG_GETARG_CHAR(n)    DatumGetChar(PG_GETARG_DATUM(n))
#define PG_GETARG_BOOL(n)    DatumGetBool(PG_GETARG_DATUM(n))
#define PG_GETARG_OID(n)     DatumGetObjectId(PG_GETARG_DATUM(n))
#define PG_GETARG_POINTER(n) DatumGetPointer(PG_GETARG_DATUM(n))
#define PG_GETARG_CSTRING(n) DatumGetCString(PG_GETARG_DATUM(n))
#define PG_GETARG_NAME(n)    DatumGetName(PG_GETARG_DATUM(n))
#define PG_GETARG_TRANSACTIONID(n)  DatumGetTransactionId(PG_GETARG_DATUM(n))
/* these macros hide the pass-by-reference-ness of the datatype: */
#define PG_GETARG_FLOAT4(n)  DatumGetFloat4(PG_GETARG_DATUM(n))
#define PG_GETARG_FLOAT8(n)  DatumGetFloat8(PG_GETARG_DATUM(n))
#define PG_GETARG_INT64(n)   DatumGetInt64(PG_GETARG_DATUM(n))
/* use this if you want the raw, possibly-toasted input datum: */
#define PG_GETARG_RAW_VARLENA_P(n)  ((struct varlena *) PG_GETARG_POINTER(n))
/* use this if you want the input datum de-toasted: */
#define PG_GETARG_VARLENA_P(n) PG_DETOAST_DATUM(PG_GETARG_DATUM(n))
/* and this if you can handle 1-byte-header datums: */
#define PG_GETARG_VARLENA_PP(n) PG_DETOAST_DATUM_PACKED(PG_GETARG_DATUM(n))
/* DatumGetFoo macros for varlena types will typically look like this: */
#define DatumGetByteaPP(X)          ((bytea *) PG_DETOAST_DATUM_PACKED(X))
#define DatumGetTextPP(X)           ((text *) PG_DETOAST_DATUM_PACKED(X))
#define DatumGetBpCharPP(X)         ((BpChar *) PG_DETOAST_DATUM_PACKED(X))
#define DatumGetVarCharPP(X)        ((VarChar *) PG_DETOAST_DATUM_PACKED(X))
#define DatumGetHeapTupleHeader(X)  ((HeapTupleHeader) PG_DETOAST_DATUM(X))
/* And we also offer variants that return an OK-to-write copy */
#define DatumGetByteaPCopy(X)       ((bytea *) PG_DETOAST_DATUM_COPY(X))
#define DatumGetTextPCopy(X)        ((text *) PG_DETOAST_DATUM_COPY(X))
#define DatumGetBpCharPCopy(X)      ((BpChar *) PG_DETOAST_DATUM_COPY(X))
#define DatumGetVarCharPCopy(X)     ((VarChar *) PG_DETOAST_DATUM_COPY(X))
#define DatumGetHeapTupleHeaderCopy(X)  ((HeapTupleHeader) PG_DETOAST_DATUM_COPY(X))
/* Variants which return n bytes starting at pos. m */
#define DatumGetByteaPSlice(X,m,n)  ((bytea *) PG_DETOAST_DATUM_SLICE(X,m,n))
#define DatumGetTextPSlice(X,m,n)   ((text *) PG_DETOAST_DATUM_SLICE(X,m,n))
#define DatumGetBpCharPSlice(X,m,n) ((BpChar *) PG_DETOAST_DATUM_SLICE(X,m,n))
#define DatumGetVarCharPSlice(X,m,n) ((VarChar *) PG_DETOAST_DATUM_SLICE(X,m,n))
/* GETARG macros for varlena types will typically look like this: */
#define PG_GETARG_BYTEA_PP(n)       DatumGetByteaPP(PG_GETARG_DATUM(n))
#define PG_GETARG_TEXT_PP(n)        DatumGetTextPP(PG_GETARG_DATUM(n))
#define PG_GETARG_BPCHAR_PP(n)      DatumGetBpCharPP(PG_GETARG_DATUM(n))
#define PG_GETARG_VARCHAR_PP(n)     DatumGetVarCharPP(PG_GETARG_DATUM(n))
#define PG_GETARG_HEAPTUPLEHEADER(n)    DatumGetHeapTupleHeader(PG_GETARG_DATUM(n))
/* And we also offer variants that return an OK-to-write copy */
#define PG_GETARG_BYTEA_P_COPY(n)   DatumGetByteaPCopy(PG_GETARG_DATUM(n))
#define PG_GETARG_TEXT_P_COPY(n)    DatumGetTextPCopy(PG_GETARG_DATUM(n))
#define PG_GETARG_BPCHAR_P_COPY(n)  DatumGetBpCharPCopy(PG_GETARG_DATUM(n))
#define PG_GETARG_VARCHAR_P_COPY(n) DatumGetVarCharPCopy(PG_GETARG_DATUM(n))
#define PG_GETARG_HEAPTUPLEHEADER_COPY(n)   DatumGetHeapTupleHeaderCopy(PG_GETARG_DATUM(n))
/* And a b-byte slice from position a -also OK to write */
#define PG_GETARG_BYTEA_P_SLICE(n,a,b) DatumGetByteaPSlice(PG_GETARG_DATUM(n),a,b)
#define PG_GETARG_TEXT_P_SLICE(n,a,b)  DatumGetTextPSlice(PG_GETARG_DATUM(n),a,b)
#define PG_GETARG_BPCHAR_P_SLICE(n,a,b) DatumGetBpCharPSlice(PG_GETARG_DATUM(n),a,b)
#define PG_GETARG_VARCHAR_P_SLICE(n,a,b) DatumGetVarCharPSlice(PG_GETARG_DATUM(n),a,b)
/*
 * Obsolescent variants that guarantee INT alignment for the return value.
 * Few operations on these particular types need alignment, mainly operations
 * that cast the VARDATA pointer to a type like int16[].  Most code should use
 * the ...PP(X) counterpart.  Nonetheless, these appear frequently in code
 * predating the PostgreSQL 8.3 introduction of the ...PP(X) variants.
 */
#define DatumGetByteaP(X)           ((bytea *) PG_DETOAST_DATUM(X))
#define DatumGetTextP(X)            ((text *) PG_DETOAST_DATUM(X))
#define DatumGetBpCharP(X)          ((BpChar *) PG_DETOAST_DATUM(X))
#define DatumGetVarCharP(X)         ((VarChar *) PG_DETOAST_DATUM(X))
#define PG_GETARG_BYTEA_P(n)        DatumGetByteaP(PG_GETARG_DATUM(n))
#define PG_GETARG_TEXT_P(n)         DatumGetTextP(PG_GETARG_DATUM(n))
#define PG_GETARG_BPCHAR_P(n)       DatumGetBpCharP(PG_GETARG_DATUM(n))
#define PG_GETARG_VARCHAR_P(n)      DatumGetVarCharP(PG_GETARG_DATUM(n))
 
/* To access options from opclass support functions use this: */
#define PG_HAS_OPCLASS_OPTIONS()    has_fn_opclass_options(fcinfo->flinfo)
#define PG_GET_OPCLASS_OPTIONS()    get_fn_opclass_options(fcinfo->flinfo)
 
/* To return a NULL do this: */
#define PG_RETURN_NULL()  \
    do { fcinfo->isnull = true; return (Datum) 0; } while (0)
 
/* A few internal functions return void (which is not the same as NULL!) */
#define PG_RETURN_VOID()     return (Datum) 0
 
/* Macros for returning results of standard types */
 
#define PG_RETURN_DATUM(x)   return (x)
#define PG_RETURN_INT32(x)   return Int32GetDatum(x)
#define PG_RETURN_UINT32(x)  return UInt32GetDatum(x)
#define PG_RETURN_INT16(x)   return Int16GetDatum(x)
#define PG_RETURN_UINT16(x)  return UInt16GetDatum(x)
#define PG_RETURN_CHAR(x)    return CharGetDatum(x)
#define PG_RETURN_BOOL(x)    return BoolGetDatum(x)
#define PG_RETURN_OID(x)     return ObjectIdGetDatum(x)
#define PG_RETURN_POINTER(x) return PointerGetDatum(x)
#define PG_RETURN_CSTRING(x) return CStringGetDatum(x)
#define PG_RETURN_NAME(x)    return NameGetDatum(x)
#define PG_RETURN_TRANSACTIONID(x)  return TransactionIdGetDatum(x)
/* these macros hide the pass-by-reference-ness of the datatype: */
#define PG_RETURN_FLOAT4(x)  return Float4GetDatum(x)
#define PG_RETURN_FLOAT8(x)  return Float8GetDatum(x)
#define PG_RETURN_INT64(x)   return Int64GetDatum(x)
#define PG_RETURN_UINT64(x)  return UInt64GetDatum(x)
/* RETURN macros for other pass-by-ref types will typically look like this: */
#define PG_RETURN_BYTEA_P(x)   PG_RETURN_POINTER(x)
#define PG_RETURN_TEXT_P(x)    PG_RETURN_POINTER(x)
#define PG_RETURN_BPCHAR_P(x)  PG_RETURN_POINTER(x)
#define PG_RETURN_VARCHAR_P(x) PG_RETURN_POINTER(x)
#define PG_RETURN_HEAPTUPLEHEADER(x)  return HeapTupleHeaderGetDatum(x)
 
 
/*-------------------------------------------------------------------------
 *      Support for detecting call convention of dynamically-loaded functions
 *
 * Dynamically loaded functions currently can only use the version-1 ("new
 * style") calling convention.  Version-0 ("old style") is not supported
 * anymore.  Version 1 is the call convention defined in this header file, and
 * must be accompanied by the macro call
 *
 *      PG_FUNCTION_INFO_V1(function_name);
 *
 * Note that internal functions do not need this decoration since they are
 * assumed to be version-1.
 *
 *-------------------------------------------------------------------------
 */
 
typedef struct
{
    int         api_version;    /* specifies call convention version number */
    /* More fields may be added later, for version numbers > 1. */
} Pg_finfo_record;
 
/* Expected signature of an info function */
typedef const Pg_finfo_record *(*PGFInfoFunction) (void);
 
/*
 *  Macro to build an info function associated with the given function name.
 *
 *  As a convenience, also provide an "extern" declaration for the given
 *  function name, so that writers of C functions need not write that too.
 *
 *  On Windows, the function and info function must be exported.  Our normal
 *  build processes take care of that via .DEF files or --export-all-symbols.
 *  Module authors using a different build process might need to manually
 *  declare the function PGDLLEXPORT.  We do that automatically here for the
 *  info function, since authors shouldn't need to be explicitly aware of it.
 */
#define PG_FUNCTION_INFO_V1(funcname) \
extern PGDLLEXPORT Datum funcname(PG_FUNCTION_ARGS); \
extern PGDLLEXPORT const Pg_finfo_record * CppConcat(pg_finfo_,funcname)(void); \
const Pg_finfo_record * \
CppConcat(pg_finfo_,funcname) (void) \
{ \
    static const Pg_finfo_record my_finfo = { 1 }; \
    return &my_finfo; \
} \
extern int no_such_variable
 
 
/*
 * Declare _PG_init/_PG_fini centrally. Historically each shared library had
 * its own declaration; but now that we want to mark these PGDLLEXPORT, using
 * central declarations avoids each extension having to add that.  Any
 * existing declarations in extensions will continue to work if fmgr.h is
 * included before them, otherwise compilation for Windows will fail.
 */
extern PGDLLEXPORT void _PG_init(void);
extern PGDLLEXPORT void _PG_fini(void);
 
 
/*-------------------------------------------------------------------------
 *      Support for verifying backend compatibility of loaded modules
 *
 * We require dynamically-loaded modules to include the macro call
 *      PG_MODULE_MAGIC;
 * so that we can check for obvious incompatibility, such as being compiled
 * for a different major PostgreSQL version.
 *
 * To compile with versions of PostgreSQL that do not support this,
 * you may put an #ifdef/#endif test around it.  Note that in a multiple-
 * source-file module, the macro call should only appear once.
 *
 * The specific items included in the magic block are intended to be ones that
 * are custom-configurable and especially likely to break dynamically loaded
 * modules if they were compiled with other values.  Also, the length field
 * can be used to detect definition changes.
 *
 * Note: we compare magic blocks with memcmp(), so there had better not be
 * any alignment pad bytes in them.
 *
 * Note: when changing the contents of magic blocks, be sure to adjust the
 * incompatible_module_error() function in dfmgr.c.
 *-------------------------------------------------------------------------
 */
 
/* Definition of the magic block structure */
typedef struct
{
    int         len;            /* sizeof(this struct) */
    int         version;        /* PostgreSQL major version */
    int         funcmaxargs;    /* FUNC_MAX_ARGS */
    int         indexmaxkeys;   /* INDEX_MAX_KEYS */
    int         namedatalen;    /* NAMEDATALEN */
    int         float8byval;    /* FLOAT8PASSBYVAL */
    char        abi_extra[32];  /* see pg_config_manual.h */
} Pg_magic_struct;
 
/* The actual data block contents */
#define PG_MODULE_MAGIC_DATA \
{ \
    sizeof(Pg_magic_struct), \
    PG_VERSION_NUM / 100, \
    FUNC_MAX_ARGS, \
    INDEX_MAX_KEYS, \
    NAMEDATALEN, \
    FLOAT8PASSBYVAL, \
    FMGR_ABI_EXTRA, \
}
 
StaticAssertDecl(sizeof(FMGR_ABI_EXTRA) <= sizeof(((Pg_magic_struct *) 0)->abi_extra),
                 "FMGR_ABI_EXTRA too long");
 
/*
 * Declare the module magic function.  It needs to be a function as the dlsym
 * in the backend is only guaranteed to work on functions, not data
 */
typedef const Pg_magic_struct *(*PGModuleMagicFunction) (void);
 
#define PG_MAGIC_FUNCTION_NAME Pg_magic_func
#define PG_MAGIC_FUNCTION_NAME_STRING "Pg_magic_func"
 
#define PG_MODULE_MAGIC \
extern PGDLLEXPORT const Pg_magic_struct *PG_MAGIC_FUNCTION_NAME(void); \
const Pg_magic_struct * \
PG_MAGIC_FUNCTION_NAME(void) \
{ \
    static const Pg_magic_struct Pg_magic_data = PG_MODULE_MAGIC_DATA; \
    return &Pg_magic_data; \
} \
extern int no_such_variable
 
 
/*-------------------------------------------------------------------------
 *      Support routines and macros for callers of fmgr-compatible functions
 *-------------------------------------------------------------------------
 */
 
/* These are for invocation of a specifically named function with a
 * directly-computed parameter list.  Note that neither arguments nor result
 * are allowed to be NULL.  Also, the function cannot be one that needs to
 * look at FmgrInfo, since there won't be any.
 */
extern Datum DirectFunctionCall1Coll(PGFunction func, Oid collation,
                                     Datum arg1);
extern Datum DirectFunctionCall2Coll(PGFunction func, Oid collation,
                                     Datum arg1, Datum arg2);
extern Datum DirectFunctionCall3Coll(PGFunction func, Oid collation,
                                     Datum arg1, Datum arg2,
                                     Datum arg3);
extern Datum DirectFunctionCall4Coll(PGFunction func, Oid collation,
                                     Datum arg1, Datum arg2,
                                     Datum arg3, Datum arg4);
extern Datum DirectFunctionCall5Coll(PGFunction func, Oid collation,
                                     Datum arg1, Datum arg2,
                                     Datum arg3, Datum arg4, Datum arg5);
extern Datum DirectFunctionCall6Coll(PGFunction func, Oid collation,
                                     Datum arg1, Datum arg2,
                                     Datum arg3, Datum arg4, Datum arg5,
                                     Datum arg6);
extern Datum DirectFunctionCall7Coll(PGFunction func, Oid collation,
                                     Datum arg1, Datum arg2,
                                     Datum arg3, Datum arg4, Datum arg5,
                                     Datum arg6, Datum arg7);
extern Datum DirectFunctionCall8Coll(PGFunction func, Oid collation,
                                     Datum arg1, Datum arg2,
                                     Datum arg3, Datum arg4, Datum arg5,
                                     Datum arg6, Datum arg7, Datum arg8);
extern Datum DirectFunctionCall9Coll(PGFunction func, Oid collation,
                                     Datum arg1, Datum arg2,
                                     Datum arg3, Datum arg4, Datum arg5,
                                     Datum arg6, Datum arg7, Datum arg8,
                                     Datum arg9);
 
/*
 * These functions work like the DirectFunctionCall functions except that
 * they use the flinfo parameter to initialise the fcinfo for the call.
 * It's recommended that the callee only use the fn_extra and fn_mcxt
 * fields, as other fields will typically describe the calling function
 * not the callee.  Conversely, the calling function should not have
 * used fn_extra, unless its use is known to be compatible with the callee's.
 */
extern Datum CallerFInfoFunctionCall1(PGFunction func, FmgrInfo *flinfo,
                                      Oid collation, Datum arg1);
extern Datum CallerFInfoFunctionCall2(PGFunction func, FmgrInfo *flinfo,
                                      Oid collation, Datum arg1, Datum arg2);
 
/* These are for invocation of a previously-looked-up function with a
 * directly-computed parameter list.  Note that neither arguments nor result
 * are allowed to be NULL.
 */
extern Datum FunctionCall0Coll(FmgrInfo *flinfo, Oid collation);
extern Datum FunctionCall1Coll(FmgrInfo *flinfo, Oid collation,
                               Datum arg1);
extern Datum FunctionCall2Coll(FmgrInfo *flinfo, Oid collation,
                               Datum arg1, Datum arg2);
extern Datum FunctionCall3Coll(FmgrInfo *flinfo, Oid collation,
                               Datum arg1, Datum arg2,
                               Datum arg3);
extern Datum FunctionCall4Coll(FmgrInfo *flinfo, Oid collation,
                               Datum arg1, Datum arg2,
                               Datum arg3, Datum arg4);
extern Datum FunctionCall5Coll(FmgrInfo *flinfo, Oid collation,
                               Datum arg1, Datum arg2,
                               Datum arg3, Datum arg4, Datum arg5);
extern Datum FunctionCall6Coll(FmgrInfo *flinfo, Oid collation,
                               Datum arg1, Datum arg2,
                               Datum arg3, Datum arg4, Datum arg5,
                               Datum arg6);
extern Datum FunctionCall7Coll(FmgrInfo *flinfo, Oid collation,
                               Datum arg1, Datum arg2,
                               Datum arg3, Datum arg4, Datum arg5,
                               Datum arg6, Datum arg7);
extern Datum FunctionCall8Coll(FmgrInfo *flinfo, Oid collation,
                               Datum arg1, Datum arg2,
                               Datum arg3, Datum arg4, Datum arg5,
                               Datum arg6, Datum arg7, Datum arg8);
extern Datum FunctionCall9Coll(FmgrInfo *flinfo, Oid collation,
                               Datum arg1, Datum arg2,
                               Datum arg3, Datum arg4, Datum arg5,
                               Datum arg6, Datum arg7, Datum arg8,
                               Datum arg9);
 
/* These are for invocation of a function identified by OID with a
 * directly-computed parameter list.  Note that neither arguments nor result
 * are allowed to be NULL.  These are essentially fmgr_info() followed by
 * FunctionCallN().  If the same function is to be invoked repeatedly, do the
 * fmgr_info() once and then use FunctionCallN().
 */
extern Datum OidFunctionCall0Coll(Oid functionId, Oid collation);
extern Datum OidFunctionCall1Coll(Oid functionId, Oid collation,
                                  Datum arg1);
extern Datum OidFunctionCall2Coll(Oid functionId, Oid collation,
                                  Datum arg1, Datum arg2);
extern Datum OidFunctionCall3Coll(Oid functionId, Oid collation,
                                  Datum arg1, Datum arg2,
                                  Datum arg3);
extern Datum OidFunctionCall4Coll(Oid functionId, Oid collation,
                                  Datum arg1, Datum arg2,
                                  Datum arg3, Datum arg4);
extern Datum OidFunctionCall5Coll(Oid functionId, Oid collation,
                                  Datum arg1, Datum arg2,
                                  Datum arg3, Datum arg4, Datum arg5);
extern Datum OidFunctionCall6Coll(Oid functionId, Oid collation,
                                  Datum arg1, Datum arg2,
                                  Datum arg3, Datum arg4, Datum arg5,
                                  Datum arg6);
extern Datum OidFunctionCall7Coll(Oid functionId, Oid collation,
                                  Datum arg1, Datum arg2,
                                  Datum arg3, Datum arg4, Datum arg5,
                                  Datum arg6, Datum arg7);
extern Datum OidFunctionCall8Coll(Oid functionId, Oid collation,
                                  Datum arg1, Datum arg2,
                                  Datum arg3, Datum arg4, Datum arg5,
                                  Datum arg6, Datum arg7, Datum arg8);
extern Datum OidFunctionCall9Coll(Oid functionId, Oid collation,
                                  Datum arg1, Datum arg2,
                                  Datum arg3, Datum arg4, Datum arg5,
                                  Datum arg6, Datum arg7, Datum arg8,
                                  Datum arg9);
 
/* These macros allow the collation argument to be omitted (with a default of
 * InvalidOid, ie, no collation).  They exist mostly for backwards
 * compatibility of source code.
 */
#define DirectFunctionCall1(func, arg1) \
    DirectFunctionCall1Coll(func, InvalidOid, arg1)
#define DirectFunctionCall2(func, arg1, arg2) \
    DirectFunctionCall2Coll(func, InvalidOid, arg1, arg2)
#define DirectFunctionCall3(func, arg1, arg2, arg3) \
    DirectFunctionCall3Coll(func, InvalidOid, arg1, arg2, arg3)
#define DirectFunctionCall4(func, arg1, arg2, arg3, arg4) \
    DirectFunctionCall4Coll(func, InvalidOid, arg1, arg2, arg3, arg4)
#define DirectFunctionCall5(func, arg1, arg2, arg3, arg4, arg5) \
    DirectFunctionCall5Coll(func, InvalidOid, arg1, arg2, arg3, arg4, arg5)
#define DirectFunctionCall6(func, arg1, arg2, arg3, arg4, arg5, arg6) \
    DirectFunctionCall6Coll(func, InvalidOid, arg1, arg2, arg3, arg4, arg5, arg6)
#define DirectFunctionCall7(func, arg1, arg2, arg3, arg4, arg5, arg6, arg7) \
    DirectFunctionCall7Coll(func, InvalidOid, arg1, arg2, arg3, arg4, arg5, arg6, arg7)
#define DirectFunctionCall8(func, arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8) \
    DirectFunctionCall8Coll(func, InvalidOid, arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8)
#define DirectFunctionCall9(func, arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9) \
    DirectFunctionCall9Coll(func, InvalidOid, arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9)
#define FunctionCall1(flinfo, arg1) \
    FunctionCall1Coll(flinfo, InvalidOid, arg1)
#define FunctionCall2(flinfo, arg1, arg2) \
    FunctionCall2Coll(flinfo, InvalidOid, arg1, arg2)
#define FunctionCall3(flinfo, arg1, arg2, arg3) \
    FunctionCall3Coll(flinfo, InvalidOid, arg1, arg2, arg3)
#define FunctionCall4(flinfo, arg1, arg2, arg3, arg4) \
    FunctionCall4Coll(flinfo, InvalidOid, arg1, arg2, arg3, arg4)
#define FunctionCall5(flinfo, arg1, arg2, arg3, arg4, arg5) \
    FunctionCall5Coll(flinfo, InvalidOid, arg1, arg2, arg3, arg4, arg5)
#define FunctionCall6(flinfo, arg1, arg2, arg3, arg4, arg5, arg6) \
    FunctionCall6Coll(flinfo, InvalidOid, arg1, arg2, arg3, arg4, arg5, arg6)
#define FunctionCall7(flinfo, arg1, arg2, arg3, arg4, arg5, arg6, arg7) \
    FunctionCall7Coll(flinfo, InvalidOid, arg1, arg2, arg3, arg4, arg5, arg6, arg7)
#define FunctionCall8(flinfo, arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8) \
    FunctionCall8Coll(flinfo, InvalidOid, arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8)
#define FunctionCall9(flinfo, arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9) \
    FunctionCall9Coll(flinfo, InvalidOid, arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9)
#define OidFunctionCall0(functionId) \
    OidFunctionCall0Coll(functionId, InvalidOid)
#define OidFunctionCall1(functionId, arg1) \
    OidFunctionCall1Coll(functionId, InvalidOid, arg1)
#define OidFunctionCall2(functionId, arg1, arg2) \
    OidFunctionCall2Coll(functionId, InvalidOid, arg1, arg2)
#define OidFunctionCall3(functionId, arg1, arg2, arg3) \
    OidFunctionCall3Coll(functionId, InvalidOid, arg1, arg2, arg3)
#define OidFunctionCall4(functionId, arg1, arg2, arg3, arg4) \
    OidFunctionCall4Coll(functionId, InvalidOid, arg1, arg2, arg3, arg4)
#define OidFunctionCall5(functionId, arg1, arg2, arg3, arg4, arg5) \
    OidFunctionCall5Coll(functionId, InvalidOid, arg1, arg2, arg3, arg4, arg5)
#define OidFunctionCall6(functionId, arg1, arg2, arg3, arg4, arg5, arg6) \
    OidFunctionCall6Coll(functionId, InvalidOid, arg1, arg2, arg3, arg4, arg5, arg6)
#define OidFunctionCall7(functionId, arg1, arg2, arg3, arg4, arg5, arg6, arg7) \
    OidFunctionCall7Coll(functionId, InvalidOid, arg1, arg2, arg3, arg4, arg5, arg6, arg7)
#define OidFunctionCall8(functionId, arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8) \
    OidFunctionCall8Coll(functionId, InvalidOid, arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8)
#define OidFunctionCall9(functionId, arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9) \
    OidFunctionCall9Coll(functionId, InvalidOid, arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9)
 
 
/* Special cases for convenient invocation of datatype I/O functions. */
extern Datum InputFunctionCall(FmgrInfo *flinfo, char *str,
                               Oid typioparam, int32 typmod);
extern bool InputFunctionCallSafe(FmgrInfo *flinfo, char *str,
                                  Oid typioparam, int32 typmod,
                                  fmNodePtr escontext,
                                  Datum *result);
extern bool DirectInputFunctionCallSafe(PGFunction func, char *str,
                                        Oid typioparam, int32 typmod,
                                        fmNodePtr escontext,
                                        Datum *result);
extern Datum OidInputFunctionCall(Oid functionId, char *str,
                                  Oid typioparam, int32 typmod);
extern char *OutputFunctionCall(FmgrInfo *flinfo, Datum val);
extern char *OidOutputFunctionCall(Oid functionId, Datum val);
extern Datum ReceiveFunctionCall(FmgrInfo *flinfo, fmStringInfo buf,
                                 Oid typioparam, int32 typmod);
extern Datum OidReceiveFunctionCall(Oid functionId, fmStringInfo buf,
                                    Oid typioparam, int32 typmod);
extern bytea *SendFunctionCall(FmgrInfo *flinfo, Datum val);
extern bytea *OidSendFunctionCall(Oid functionId, Datum val);
 
 
/*
 * Routines in fmgr.c
 */
extern const Pg_finfo_record *fetch_finfo_record(void *filehandle, const char *funcname);
extern Oid  fmgr_internal_function(const char *proname);
extern Oid  get_fn_expr_rettype(FmgrInfo *flinfo);
extern Oid  get_fn_expr_argtype(FmgrInfo *flinfo, int argnum);
extern Oid  get_call_expr_argtype(fmNodePtr expr, int argnum);
extern bool get_fn_expr_arg_stable(FmgrInfo *flinfo, int argnum);
extern bool get_call_expr_arg_stable(fmNodePtr expr, int argnum);
extern bool get_fn_expr_variadic(FmgrInfo *flinfo);
extern bytea *get_fn_opclass_options(FmgrInfo *flinfo);
extern bool has_fn_opclass_options(FmgrInfo *flinfo);
extern void set_fn_opclass_options(FmgrInfo *flinfo, bytea *options);
extern bool CheckFunctionValidatorAccess(Oid validatorOid, Oid functionOid);
 
/*
 * Routines in dfmgr.c
 */
extern PGDLLIMPORT char *Dynamic_library_path;
 
extern void *load_external_function(const char *filename, const char *funcname,
                                    bool signalNotFound, void **filehandle);
extern void *lookup_external_function(void *filehandle, const char *funcname);
extern void load_file(const char *filename, bool restricted);
extern void **find_rendezvous_variable(const char *varName);
extern Size EstimateLibraryStateSpace(void);
extern void SerializeLibraryState(Size maxsize, char *start_address);
extern void RestoreLibraryState(char *start_address);
 
/*
 * Support for aggregate functions
 *
 * These are actually in executor/nodeAgg.c, but we declare them here since
 * the whole point is for callers to not be overly friendly with nodeAgg.
 */
 
/* AggCheckCallContext can return one of the following codes, or 0: */
#define AGG_CONTEXT_AGGREGATE   1   /* regular aggregate */
#define AGG_CONTEXT_WINDOW      2   /* window function */
 
extern int  AggCheckCallContext(FunctionCallInfo fcinfo,
                                MemoryContext *aggcontext);
extern fmAggrefPtr AggGetAggref(FunctionCallInfo fcinfo);
extern MemoryContext AggGetTempMemoryContext(FunctionCallInfo fcinfo);
extern bool AggStateIsShared(FunctionCallInfo fcinfo);
extern void AggRegisterCallback(FunctionCallInfo fcinfo,
                                fmExprContextCallbackFunction func,
                                Datum arg);
 
/*
 * We allow plugin modules to hook function entry/exit.  This is intended
 * as support for loadable security policy modules, which may want to
 * perform additional privilege checks on function entry or exit, or to do
 * other internal bookkeeping.  To make this possible, such modules must be
 * able not only to support normal function entry and exit, but also to trap
 * the case where we bail out due to an error; and they must also be able to
 * prevent inlining.
 */
typedef enum FmgrHookEventType
{
    FHET_START,
    FHET_END,
    FHET_ABORT
} FmgrHookEventType;
 
typedef bool (*needs_fmgr_hook_type) (Oid fn_oid);
 
typedef void (*fmgr_hook_type) (FmgrHookEventType event,
                                FmgrInfo *flinfo, Datum *arg);
 
extern PGDLLIMPORT needs_fmgr_hook_type needs_fmgr_hook;
extern PGDLLIMPORT fmgr_hook_type fmgr_hook;
 
#define FmgrHookIsNeeded(fn_oid)                            \
    (!needs_fmgr_hook ? false : (*needs_fmgr_hook)(fn_oid))
 
#endif                          /* FMGR_H */