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postgresql/src/include/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) 1996-2019, 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"
#include "utils/elog.h"
#include "utils/palloc.h"
/* ----------------------------------------------------------------
* 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 va_extsize < 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) */
int32 va_extsize; /* External saved size (doesn't) */
Oid va_valueid; /* Unique ID of value within TOAST table */
Oid va_toastrelid; /* RelID of TOAST table containing it */
} varatt_external;
/*
* 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_rawsize; /* Original data size (excludes header) */
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 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)
#define VARHDRSZ_EXTERNAL offsetof(varattrib_1b_e, va_data)
#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)
#define VARRAWSIZE_4B_C(PTR) \
(((varattrib_4b *) (PTR))->va_compressed.va_rawsize)
/* Externally visible 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.
*
* 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))
/* ----------------------------------------------------------------
* 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 */
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