postgres.h

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/*-------------------------------------------------------------------------
 *
 * postgres.h
 *    Primary include file for PostgreSQL server .c files
 *
 * This should be the first file included by PostgreSQL backend modules.
 * Client-side code should include postgres_fe.h instead.
 *
 *
 * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
 * Portions Copyright (c) 1995, Regents of the University of California
 *
 * src/include/postgres.h
 *
 *-------------------------------------------------------------------------
 */
/*
 *----------------------------------------------------------------
 *   TABLE OF CONTENTS
 *
 *    When adding stuff to this file, please try to put stuff
 *    into the relevant section, or add new sections as appropriate.
 *
 *    section  description
 *    -------  ------------------------------------------------
 *    1)    variable-length datatypes (TOAST support)
 *    2)    Datum type + support macros
 *
 *   NOTES
 *
 *  In general, this file should contain declarations that are widely needed
 *  in the backend environment, but are of no interest outside the backend.
 *
 *  Simple type definitions live in c.h, where they are shared with
 *  postgres_fe.h.  We do that since those type definitions are needed by
 *  frontend modules that want to deal with binary data transmission to or
 *  from the backend.  Type definitions in this file should be for
 *  representations that never escape the backend, such as Datum or
 *  TOASTed varlena objects.
 *
 *----------------------------------------------------------------
 */
#ifndef POSTGRES_H
#define POSTGRES_H
 
#include "c.h"
 
/*
 * MEOS: redefining elog
 * If WIN32 is set ERROR is defined in wingdi.h as #define ERROR 0
 * and is imported through windows.h. Since in MEOS we do not use ERROR
 * but keep it so elog(ERROR, "xxx") can be both used in MEOS and in PostgreSQL
 * as soon as it is defined everything works fine.
 */
#define INFO      17      /* Messages specifically requested by user (eg
                 * VACUUM VERBOSE output); always sent to
                 * client regardless of client_min_messages,
                 * but by default not sent to server log. */
#define NOTICE    18      /* Helpful messages to users about query
                 * operation; sent to client and not to server
                 * log by default. */
#define WARNING    19      /* Warnings.  NOTICE is for expected messages
                 * like implicit sequence creation by SERIAL.
                 * WARNING is for unexpected messages. */
#ifndef ERROR
#define ERROR    21  /* user error - abort transaction; return to known state */
#endif
#define EXIT_FAILURE 1
 
/* MEOS: redefining palloc0, palloc, and pfree */
#if MEOS
#define palloc0(X) (calloc(1, X))
#define palloc malloc
#define repalloc realloc
#define pfree free
#define pstrdup strdup
#endif /* MEOS */
 
/* ----------------------------------------------------------------
 *        Section 1:  variable-length datatypes (TOAST support)
 * ----------------------------------------------------------------
 */
 
/*
 * struct varatt_external is a traditional "TOAST pointer", that is, the
 * information needed to fetch a Datum stored out-of-line in a TOAST table.
 * The data is compressed if and only if the external size stored in
 * va_extinfo is less than va_rawsize - VARHDRSZ.
 *
 * This struct must not contain any padding, because we sometimes compare
 * these pointers using memcmp.
 *
 * Note that this information is stored unaligned within actual tuples, so
 * you need to memcpy from the tuple into a local struct variable before
 * you can look at these fields!  (The reason we use memcmp is to avoid
 * having to do that just to detect equality of two TOAST pointers...)
 */
typedef struct varatt_external
{
  int32    va_rawsize;     /* Original data size (includes header) */
  uint32    va_extinfo;    /* External saved size (without header) and
                            * compression method */
  Oid      va_valueid;     /* Unique ID of value within TOAST table */
  Oid      va_toastrelid;  /* RelID of TOAST table containing it */
}      varatt_external;
 
/*
 * These macros define the "saved size" portion of va_extinfo.  Its remaining
 * two high-order bits identify the compression method.
 */
#define VARLENA_EXTSIZE_BITS  30
#define VARLENA_EXTSIZE_MASK  ((1U << VARLENA_EXTSIZE_BITS) - 1)
 
/*
 * struct varatt_indirect is a "TOAST pointer" representing an out-of-line
 * Datum that's stored in memory, not in an external toast relation.
 * The creator of such a Datum is entirely responsible that the referenced
 * storage survives for as long as referencing pointer Datums can exist.
 *
 * Note that just as for struct varatt_external, this struct is stored
 * unaligned within any containing tuple.
 */
typedef struct varatt_indirect
{
  struct varlena *pointer;  /* Pointer to in-memory varlena */
}      varatt_indirect;
 
/*
 * struct varatt_expanded is a "TOAST pointer" representing an out-of-line
 * Datum that is stored in memory, in some type-specific, not necessarily
 * physically contiguous format that is convenient for computation not
 * storage.  APIs for this, in particular the definition of struct
 * ExpandedObjectHeader, are in src/include/utils/expandeddatum.h.
 *
 * Note that just as for struct varatt_external, this struct is stored
 * unaligned within any containing tuple.
 */
typedef struct ExpandedObjectHeader ExpandedObjectHeader;
 
typedef struct varatt_expanded
{
  ExpandedObjectHeader *eohptr;
} varatt_expanded;
 
/*
 * Type tag for the various sorts of "TOAST pointer" datums.  The peculiar
 * value for VARTAG_ONDISK comes from a requirement for on-disk compatibility
 * with a previous notion that the tag field was the pointer datum's length.
 */
typedef enum vartag_external
{
  VARTAG_INDIRECT = 1,
  VARTAG_EXPANDED_RO = 2,
  VARTAG_EXPANDED_RW = 3,
  VARTAG_ONDISK = 18
} vartag_external;
 
/* this test relies on the specific tag values above */
#define VARTAG_IS_EXPANDED(tag) \
  (((tag) & ~1) == VARTAG_EXPANDED_RO)
 
#define VARTAG_SIZE(tag) \
  ((tag) == VARTAG_INDIRECT ? sizeof(varatt_indirect) : \
   VARTAG_IS_EXPANDED(tag) ? sizeof(varatt_expanded) : \
   (tag) == VARTAG_ONDISK ? sizeof(varatt_external) : \
   TrapMacro(true, "unrecognized TOAST vartag"))
 
/*
 * These structs describe the header of a varlena object that may have been
 * TOASTed.  Generally, don't reference these structs directly, but use the
 * macros below.
 *
 * We use separate structs for the aligned and unaligned cases because the
 * compiler might otherwise think it could generate code that assumes
 * alignment while touching fields of a 1-byte-header varlena.
 */
typedef union
{
  struct            /* Normal varlena (4-byte length) */
  {
    uint32    va_header;
    char    va_data[FLEXIBLE_ARRAY_MEMBER];
  }      va_4byte;
  struct            /* Compressed-in-line format */
  {
    uint32    va_header;
    uint32    va_tcinfo;  /* Original data size (excludes header) and
                 * compression method; see va_extinfo */
    char    va_data[FLEXIBLE_ARRAY_MEMBER]; /* Compressed data */
  }      va_compressed;
} varattrib_4b;
 
typedef struct
{
  uint8    va_header;
  char    va_data[FLEXIBLE_ARRAY_MEMBER]; /* Data begins here */
} varattrib_1b;
 
/* TOAST pointers are a subset of varattrib_1b with an identifying tag byte */
typedef struct
{
  uint8    va_header;    /* Always 0x80 or 0x01 */
  uint8    va_tag;      /* Type of datum */
  char    va_data[FLEXIBLE_ARRAY_MEMBER]; /* Type-specific data */
} varattrib_1b_e;
 
/*
 * Bit layouts for varlena headers on big-endian machines:
 *
 * 00xxxxxx 4-byte length word, aligned, uncompressed data (up to 1G)
 * 01xxxxxx 4-byte length word, aligned, *compressed* data (up to 1G)
 * 10000000 1-byte length word, unaligned, TOAST pointer
 * 1xxxxxxx 1-byte length word, unaligned, uncompressed data (up to 126b)
 *
 * Bit layouts for varlena headers on little-endian machines:
 *
 * xxxxxx00 4-byte length word, aligned, uncompressed data (up to 1G)
 * xxxxxx10 4-byte length word, aligned, *compressed* data (up to 1G)
 * 00000001 1-byte length word, unaligned, TOAST pointer
 * xxxxxxx1 1-byte length word, unaligned, uncompressed data (up to 126b)
 *
 * The "xxx" bits are the length field (which includes itself in all cases).
 * In the big-endian case we mask to extract the length, in the little-endian
 * case we shift.  Note that in both cases the flag bits are in the physically
 * first byte.  Also, it is not possible for a 1-byte length word to be zero;
 * this lets us disambiguate alignment padding bytes from the start of an
 * unaligned datum.  (We now *require* pad bytes to be filled with zero!)
 *
 * In TOAST pointers the va_tag field (see varattrib_1b_e) is used to discern
 * the specific type and length of the pointer datum.
 */
 
/*
 * Endian-dependent macros.  These are considered internal --- use the
 * external macros below instead of using these directly.
 *
 * Note: IS_1B is true for external toast records but VARSIZE_1B will return 0
 * for such records. Hence you should usually check for IS_EXTERNAL before
 * checking for IS_1B.
 */
 
#ifdef WORDS_BIGENDIAN
 
#define VARATT_IS_4B(PTR) \
  ((((varattrib_1b *) (PTR))->va_header & 0x80) == 0x00)
#define VARATT_IS_4B_U(PTR) \
  ((((varattrib_1b *) (PTR))->va_header & 0xC0) == 0x00)
#define VARATT_IS_4B_C(PTR) \
  ((((varattrib_1b *) (PTR))->va_header & 0xC0) == 0x40)
#define VARATT_IS_1B(PTR) \
  ((((varattrib_1b *) (PTR))->va_header & 0x80) == 0x80)
#define VARATT_IS_1B_E(PTR) \
  ((((varattrib_1b *) (PTR))->va_header) == 0x80)
#define VARATT_NOT_PAD_BYTE(PTR) \
  (*((uint8 *) (PTR)) != 0)
 
/* VARSIZE_4B() should only be used on known-aligned data */
#define VARSIZE_4B(PTR) \
  (((varattrib_4b *) (PTR))->va_4byte.va_header & 0x3FFFFFFF)
#define VARSIZE_1B(PTR) \
  (((varattrib_1b *) (PTR))->va_header & 0x7F)
#define VARTAG_1B_E(PTR) \
  (((varattrib_1b_e *) (PTR))->va_tag)
 
#define SET_VARSIZE_4B(PTR,len) \
  (((varattrib_4b *) (PTR))->va_4byte.va_header = (len) & 0x3FFFFFFF)
#define SET_VARSIZE_4B_C(PTR,len) \
  (((varattrib_4b *) (PTR))->va_4byte.va_header = ((len) & 0x3FFFFFFF) | 0x40000000)
#define SET_VARSIZE_1B(PTR,len) \
  (((varattrib_1b *) (PTR))->va_header = (len) | 0x80)
#define SET_VARTAG_1B_E(PTR,tag) \
  (((varattrib_1b_e *) (PTR))->va_header = 0x80, \
   ((varattrib_1b_e *) (PTR))->va_tag = (tag))
 
#else              /* !WORDS_BIGENDIAN */
 
#define VARATT_IS_4B(PTR) \
  ((((varattrib_1b *) (PTR))->va_header & 0x01) == 0x00)
#define VARATT_IS_4B_U(PTR) \
  ((((varattrib_1b *) (PTR))->va_header & 0x03) == 0x00)
#define VARATT_IS_4B_C(PTR) \
  ((((varattrib_1b *) (PTR))->va_header & 0x03) == 0x02)
#define VARATT_IS_1B(PTR) \
  ((((varattrib_1b *) (PTR))->va_header & 0x01) == 0x01)
#define VARATT_IS_1B_E(PTR) \
  ((((varattrib_1b *) (PTR))->va_header) == 0x01)
#define VARATT_NOT_PAD_BYTE(PTR) \
  (*((uint8 *) (PTR)) != 0)
 
/* VARSIZE_4B() should only be used on known-aligned data */
#define VARSIZE_4B(PTR) \
  ((((varattrib_4b *) (PTR))->va_4byte.va_header >> 2) & 0x3FFFFFFF)
#define VARSIZE_1B(PTR) \
  ((((varattrib_1b *) (PTR))->va_header >> 1) & 0x7F)
#define VARTAG_1B_E(PTR) \
  (((varattrib_1b_e *) (PTR))->va_tag)
 
#define SET_VARSIZE_4B(PTR,len) \
  (((varattrib_4b *) (PTR))->va_4byte.va_header = (((uint32) (len)) << 2))
#define SET_VARSIZE_4B_C(PTR,len) \
  (((varattrib_4b *) (PTR))->va_4byte.va_header = (((uint32) (len)) << 2) | 0x02)
#define SET_VARSIZE_1B(PTR,len) \
  (((varattrib_1b *) (PTR))->va_header = (((uint8) (len)) << 1) | 0x01)
#define SET_VARTAG_1B_E(PTR,tag) \
  (((varattrib_1b_e *) (PTR))->va_header = 0x01, \
   ((varattrib_1b_e *) (PTR))->va_tag = (tag))
 
#endif              /* WORDS_BIGENDIAN */
 
#define VARDATA_4B(PTR)    (((varattrib_4b *) (PTR))->va_4byte.va_data)
#define VARDATA_4B_C(PTR)  (((varattrib_4b *) (PTR))->va_compressed.va_data)
#define VARDATA_1B(PTR)    (((varattrib_1b *) (PTR))->va_data)
#define VARDATA_1B_E(PTR)  (((varattrib_1b_e *) (PTR))->va_data)
 
/*
 * Externally visible TOAST macros begin here.
 */
 
#define VARHDRSZ_EXTERNAL    offsetof(varattrib_1b_e, va_data)
#define VARHDRSZ_COMPRESSED    offsetof(varattrib_4b, va_compressed.va_data)
#define VARHDRSZ_SHORT      offsetof(varattrib_1b, va_data)
 
#define VARATT_SHORT_MAX    0x7F
#define VARATT_CAN_MAKE_SHORT(PTR) \
  (VARATT_IS_4B_U(PTR) && \
   (VARSIZE(PTR) - VARHDRSZ + VARHDRSZ_SHORT) <= VARATT_SHORT_MAX)
#define VARATT_CONVERTED_SHORT_SIZE(PTR) \
  (VARSIZE(PTR) - VARHDRSZ + VARHDRSZ_SHORT)
 
/*
 * 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.
 *
 * Code assembling a new datum should call VARDATA() and SET_VARSIZE().
 * (Datums begin life untoasted.)
 *
 * Other macros here should usually be used only by tuple assembly/disassembly
 * code and code that specifically wants to work with still-toasted Datums.
 */
#define VARDATA(PTR)            VARDATA_4B(PTR)
#define VARSIZE(PTR)            VARSIZE_4B(PTR)
 
#define VARSIZE_SHORT(PTR)          VARSIZE_1B(PTR)
#define VARDATA_SHORT(PTR)          VARDATA_1B(PTR)
 
#define VARTAG_EXTERNAL(PTR)        VARTAG_1B_E(PTR)
#define VARSIZE_EXTERNAL(PTR)        (VARHDRSZ_EXTERNAL + VARTAG_SIZE(VARTAG_EXTERNAL(PTR)))
#define VARDATA_EXTERNAL(PTR)        VARDATA_1B_E(PTR)
 
#define VARATT_IS_COMPRESSED(PTR)      VARATT_IS_4B_C(PTR)
#define VARATT_IS_EXTERNAL(PTR)        VARATT_IS_1B_E(PTR)
#define VARATT_IS_EXTERNAL_ONDISK(PTR) \
  (VARATT_IS_EXTERNAL(PTR) && VARTAG_EXTERNAL(PTR) == VARTAG_ONDISK)
#define VARATT_IS_EXTERNAL_INDIRECT(PTR) \
  (VARATT_IS_EXTERNAL(PTR) && VARTAG_EXTERNAL(PTR) == VARTAG_INDIRECT)
#define VARATT_IS_EXTERNAL_EXPANDED_RO(PTR) \
  (VARATT_IS_EXTERNAL(PTR) && VARTAG_EXTERNAL(PTR) == VARTAG_EXPANDED_RO)
#define VARATT_IS_EXTERNAL_EXPANDED_RW(PTR) \
  (VARATT_IS_EXTERNAL(PTR) && VARTAG_EXTERNAL(PTR) == VARTAG_EXPANDED_RW)
#define VARATT_IS_EXTERNAL_EXPANDED(PTR) \
  (VARATT_IS_EXTERNAL(PTR) && VARTAG_IS_EXPANDED(VARTAG_EXTERNAL(PTR)))
#define VARATT_IS_EXTERNAL_NON_EXPANDED(PTR) \
  (VARATT_IS_EXTERNAL(PTR) && !VARTAG_IS_EXPANDED(VARTAG_EXTERNAL(PTR)))
#define VARATT_IS_SHORT(PTR)        VARATT_IS_1B(PTR)
#define VARATT_IS_EXTENDED(PTR)        (!VARATT_IS_4B_U(PTR))
 
#define SET_VARSIZE(PTR, len)        SET_VARSIZE_4B(PTR, len)
#define SET_VARSIZE_SHORT(PTR, len)      SET_VARSIZE_1B(PTR, len)
#define SET_VARSIZE_COMPRESSED(PTR, len)  SET_VARSIZE_4B_C(PTR, len)
 
#define SET_VARTAG_EXTERNAL(PTR, tag)    SET_VARTAG_1B_E(PTR, tag)
 
#define VARSIZE_ANY(PTR) \
  (VARATT_IS_1B_E(PTR) ? VARSIZE_EXTERNAL(PTR) : \
   (VARATT_IS_1B(PTR) ? VARSIZE_1B(PTR) : \
    VARSIZE_4B(PTR)))
 
/* Size of a varlena data, excluding header */
#define VARSIZE_ANY_EXHDR(PTR) \
  (VARATT_IS_1B_E(PTR) ? VARSIZE_EXTERNAL(PTR)-VARHDRSZ_EXTERNAL : \
   (VARATT_IS_1B(PTR) ? VARSIZE_1B(PTR)-VARHDRSZ_SHORT : \
    VARSIZE_4B(PTR)-VARHDRSZ))
 
/* caution: this will not work on an external or compressed-in-line Datum */
/* caution: this will return a possibly unaligned pointer */
#define VARDATA_ANY(PTR) \
   (VARATT_IS_1B(PTR) ? VARDATA_1B(PTR) : VARDATA_4B(PTR))
 
/* Decompressed size and compression method of a compressed-in-line Datum */
#define VARDATA_COMPRESSED_GET_EXTSIZE(PTR) \
  (((varattrib_4b *) (PTR))->va_compressed.va_tcinfo & VARLENA_EXTSIZE_MASK)
#define VARDATA_COMPRESSED_GET_COMPRESS_METHOD(PTR) \
  (((varattrib_4b *) (PTR))->va_compressed.va_tcinfo >> VARLENA_EXTSIZE_BITS)
 
/* Same for external Datums; but note argument is a struct varatt_external */
#define VARATT_EXTERNAL_GET_EXTSIZE(toast_pointer) \
  ((toast_pointer).va_extinfo & VARLENA_EXTSIZE_MASK)
#define VARATT_EXTERNAL_GET_COMPRESS_METHOD(toast_pointer) \
  ((toast_pointer).va_extinfo >> VARLENA_EXTSIZE_BITS)
 
#define VARATT_EXTERNAL_SET_SIZE_AND_COMPRESS_METHOD(toast_pointer, len, cm) \
  do { \
    Assert((cm) == TOAST_PGLZ_COMPRESSION_ID || \
         (cm) == TOAST_LZ4_COMPRESSION_ID); \
    ((toast_pointer).va_extinfo = \
      (len) | ((uint32) (cm) << VARLENA_EXTSIZE_BITS)); \
  } while (0)
 
/*
 * Testing whether an externally-stored value is compressed now requires
 * comparing size stored in va_extinfo (the actual length of the external data)
 * to rawsize (the original uncompressed datum's size).  The latter includes
 * VARHDRSZ overhead, the former doesn't.  We never use compression unless it
 * actually saves space, so we expect either equality or less-than.
 */
#define VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer) \
  (VARATT_EXTERNAL_GET_EXTSIZE(toast_pointer) < \
   (toast_pointer).va_rawsize - VARHDRSZ)
 
 
/* ----------------------------------------------------------------
 *        Section 2:  Datum type + support macros
 * ----------------------------------------------------------------
 */
 
/*
 * A Datum contains either a value of a pass-by-value type or a pointer to a
 * value of a pass-by-reference type.  Therefore, we require:
 *
 * sizeof(Datum) == sizeof(void *) == 4 or 8
 *
 * The macros below and the analogous macros for other types should be used to
 * convert between a Datum and the appropriate C type.
 */
 
typedef uintptr_t Datum;
 
/*
 * A NullableDatum is used in places where both a Datum and its nullness needs
 * to be stored. This can be more efficient than storing datums and nullness
 * in separate arrays, due to better spatial locality, even if more space may
 * be wasted due to padding.
 */
typedef struct NullableDatum
{
#define FIELDNO_NULLABLE_DATUM_DATUM 0
  Datum    value;
#define FIELDNO_NULLABLE_DATUM_ISNULL 1
  bool    isnull;
  /* due to alignment padding this could be used for flags for free */
} NullableDatum;
 
#define SIZEOF_DATUM SIZEOF_VOID_P
 
/*
 * DatumGetBool
 *    Returns boolean value of a datum.
 *
 * Note: any nonzero value will be considered true.
 */
 
#define DatumGetBool(X) ((bool) ((X) != 0))
 
/*
 * BoolGetDatum
 *    Returns datum representation for a boolean.
 *
 * Note: any nonzero value will be considered true.
 */
 
#define BoolGetDatum(X) ((Datum) ((X) ? 1 : 0))
 
/*
 * DatumGetChar
 *    Returns character value of a datum.
 */
 
#define DatumGetChar(X) ((char) (X))
 
/*
 * CharGetDatum
 *    Returns datum representation for a character.
 */
 
#define CharGetDatum(X) ((Datum) (X))
 
/*
 * Int8GetDatum
 *    Returns datum representation for an 8-bit integer.
 */
 
#define Int8GetDatum(X) ((Datum) (X))
 
/*
 * DatumGetUInt8
 *    Returns 8-bit unsigned integer value of a datum.
 */
 
#define DatumGetUInt8(X) ((uint8) (X))
 
/*
 * UInt8GetDatum
 *    Returns datum representation for an 8-bit unsigned integer.
 */
 
#define UInt8GetDatum(X) ((Datum) (X))
 
/*
 * DatumGetInt16
 *    Returns 16-bit integer value of a datum.
 */
 
#define DatumGetInt16(X) ((int16) (X))
 
/*
 * Int16GetDatum
 *    Returns datum representation for a 16-bit integer.
 */
 
#define Int16GetDatum(X) ((Datum) (X))
 
/*
 * DatumGetUInt16
 *    Returns 16-bit unsigned integer value of a datum.
 */
 
#define DatumGetUInt16(X) ((uint16) (X))
 
/*
 * UInt16GetDatum
 *    Returns datum representation for a 16-bit unsigned integer.
 */
 
#define UInt16GetDatum(X) ((Datum) (X))
 
/*
 * DatumGetInt32
 *    Returns 32-bit integer value of a datum.
 */
 
#define DatumGetInt32(X) ((int32) (X))
 
/*
 * Int32GetDatum
 *    Returns datum representation for a 32-bit integer.
 */
 
#define Int32GetDatum(X) ((Datum) (X))
 
/*
 * DatumGetUInt32
 *    Returns 32-bit unsigned integer value of a datum.
 */
 
#define DatumGetUInt32(X) ((uint32) (X))
 
/*
 * UInt32GetDatum
 *    Returns datum representation for a 32-bit unsigned integer.
 */
 
#define UInt32GetDatum(X) ((Datum) (X))
 
/*
 * DatumGetObjectId
 *    Returns object identifier value of a datum.
 */
 
#define DatumGetObjectId(X) ((Oid) (X))
 
/*
 * ObjectIdGetDatum
 *    Returns datum representation for an object identifier.
 */
 
#define ObjectIdGetDatum(X) ((Datum) (X))
 
/*
 * DatumGetTransactionId
 *    Returns transaction identifier value of a datum.
 */
 
#define DatumGetTransactionId(X) ((TransactionId) (X))
 
/*
 * TransactionIdGetDatum
 *    Returns datum representation for a transaction identifier.
 */
 
#define TransactionIdGetDatum(X) ((Datum) (X))
 
/*
 * MultiXactIdGetDatum
 *    Returns datum representation for a multixact identifier.
 */
 
#define MultiXactIdGetDatum(X) ((Datum) (X))
 
/*
 * DatumGetCommandId
 *    Returns command identifier value of a datum.
 */
 
#define DatumGetCommandId(X) ((CommandId) (X))
 
/*
 * CommandIdGetDatum
 *    Returns datum representation for a command identifier.
 */
 
#define CommandIdGetDatum(X) ((Datum) (X))
 
/*
 * DatumGetPointer
 *    Returns pointer value of a datum.
 */
 
#define DatumGetPointer(X) ((Pointer) (X))
 
/*
 * PointerGetDatum
 *    Returns datum representation for a pointer.
 */
 
#define PointerGetDatum(X) ((Datum) (X))
 
/*
 * DatumGetCString
 *    Returns C string (null-terminated string) value of a datum.
 *
 * Note: C string is not a full-fledged Postgres type at present,
 * but type input functions use this conversion for their inputs.
 */
 
#define DatumGetCString(X) ((char *) DatumGetPointer(X))
 
/*
 * CStringGetDatum
 *    Returns datum representation for a C string (null-terminated string).
 *
 * Note: C string is not a full-fledged Postgres type at present,
 * but type output functions use this conversion for their outputs.
 * Note: CString is pass-by-reference; caller must ensure the pointed-to
 * value has adequate lifetime.
 */
 
#define CStringGetDatum(X) PointerGetDatum(X)
 
/*
 * DatumGetName
 *    Returns name value of a datum.
 */
 
#define DatumGetName(X) ((Name) DatumGetPointer(X))
 
/*
 * NameGetDatum
 *    Returns datum representation for a name.
 *
 * Note: Name is pass-by-reference; caller must ensure the pointed-to
 * value has adequate lifetime.
 */
 
#define NameGetDatum(X) CStringGetDatum(NameStr(*(X)))
 
/*
 * DatumGetInt64
 *    Returns 64-bit integer value of a datum.
 *
 * Note: this macro hides whether int64 is pass by value or by reference.
 */
 
#ifdef USE_FLOAT8_BYVAL
#define DatumGetInt64(X) ((int64) (X))
#else
#define DatumGetInt64(X) (* ((int64 *) DatumGetPointer(X)))
#endif
 
/*
 * Int64GetDatum
 *    Returns datum representation for a 64-bit integer.
 *
 * Note: if int64 is pass by reference, this function returns a reference
 * to palloc'd space.
 */
 
#ifdef USE_FLOAT8_BYVAL
#define Int64GetDatum(X) ((Datum) (X))
#else
extern Datum Int64GetDatum(int64 X);
#endif
 
/*
 * DatumGetUInt64
 *    Returns 64-bit unsigned integer value of a datum.
 *
 * Note: this macro hides whether int64 is pass by value or by reference.
 */
 
#ifdef USE_FLOAT8_BYVAL
#define DatumGetUInt64(X) ((uint64) (X))
#else
#define DatumGetUInt64(X) (* ((uint64 *) DatumGetPointer(X)))
#endif
 
/*
 * UInt64GetDatum
 *    Returns datum representation for a 64-bit unsigned integer.
 *
 * Note: if int64 is pass by reference, this function returns a reference
 * to palloc'd space.
 */
 
#ifdef USE_FLOAT8_BYVAL
#define UInt64GetDatum(X) ((Datum) (X))
#else
#define UInt64GetDatum(X) Int64GetDatum((int64) (X))
#endif
 
/*
 * Float <-> Datum conversions
 *
 * These have to be implemented as inline functions rather than macros, when
 * passing by value, because many machines pass int and float function
 * parameters/results differently; so we need to play weird games with unions.
 */
 
/*
 * DatumGetFloat4
 *    Returns 4-byte floating point value of a datum.
 */
static inline float4
DatumGetFloat4(Datum X)
{
  union
  {
    int32    value;
    float4    retval;
  }      myunion;
 
  myunion.value = DatumGetInt32(X);
  return myunion.retval;
}
 
/*
 * Float4GetDatum
 *    Returns datum representation for a 4-byte floating point number.
 */
static inline Datum
Float4GetDatum(float4 X)
{
  union
  {
    float4    value;
    int32    retval;
  }      myunion;
 
  myunion.value = X;
  return Int32GetDatum(myunion.retval);
}
 
/*
 * DatumGetFloat8
 *    Returns 8-byte floating point value of a datum.
 *
 * Note: this macro hides whether float8 is pass by value or by reference.
 */
 
#ifdef USE_FLOAT8_BYVAL
static inline float8
DatumGetFloat8(Datum X)
{
  union
  {
    int64    value;
    float8    retval;
  }      myunion;
 
  myunion.value = DatumGetInt64(X);
  return myunion.retval;
}
#else
#define DatumGetFloat8(X) (* ((float8 *) DatumGetPointer(X)))
#endif
 
/*
 * Float8GetDatum
 *    Returns datum representation for an 8-byte floating point number.
 *
 * Note: if float8 is pass by reference, this function returns a reference
 * to palloc'd space.
 */
 
#ifdef USE_FLOAT8_BYVAL
static inline Datum
Float8GetDatum(float8 X)
{
  union
  {
    float8    value;
    int64    retval;
  }      myunion;
 
  myunion.value = X;
  return Int64GetDatum(myunion.retval);
}
#else
extern Datum Float8GetDatum(float8 X);
#endif
 
 
/*
 * Int64GetDatumFast
 * Float8GetDatumFast
 *
 * These macros are intended to allow writing code that does not depend on
 * whether int64 and float8 are pass-by-reference types, while not
 * sacrificing performance when they are.  The argument must be a variable
 * that will exist and have the same value for as long as the Datum is needed.
 * In the pass-by-ref case, the address of the variable is taken to use as
 * the Datum.  In the pass-by-val case, these will be the same as the non-Fast
 * macros.
 */
 
#ifdef USE_FLOAT8_BYVAL
#define Int64GetDatumFast(X)  Int64GetDatum(X)
#define Float8GetDatumFast(X) Float8GetDatum(X)
#else
#define Int64GetDatumFast(X)  PointerGetDatum(&(X))
#define Float8GetDatumFast(X) PointerGetDatum(&(X))
#endif
 
#endif              /* POSTGRES_H */