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/*-------------------------------------------------------------------------
*
* itup.h
* POSTGRES index tuple definitions.
*
*
* Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/access/itup.h
*
*-------------------------------------------------------------------------
*/
#ifndef ITUP_H
#define ITUP_H
#include "access/tupdesc.h"
#include "access/tupmacs.h"
#include "storage/bufpage.h"
#include "storage/itemptr.h"
/*
* Index tuple header structure
*
* All index tuples start with IndexTupleData. If the HasNulls bit is set,
* this is followed by an IndexAttributeBitMapData. The index attribute
* values follow, beginning at a MAXALIGN boundary.
*
* Note that the space allocated for the bitmap does not vary with the number
* of attributes; that is because we don't have room to store the number of
* attributes in the header. Given the MAXALIGN constraint there's no space
* savings to be had anyway, for usual values of INDEX_MAX_KEYS.
*/
typedef struct IndexTupleData
{
ItemPointerData t_tid; /* reference TID to heap tuple */
/* ---------------
* t_info is laid out in the following fashion:
*
* 15th (high) bit: has nulls
* 14th bit: has var-width attributes
* 13th bit: AM-defined meaning
* 12-0 bit: size of tuple
* ---------------
*/
unsigned short t_info; /* various info about tuple */
} IndexTupleData; /* MORE DATA FOLLOWS AT END OF STRUCT */
typedef IndexTupleData *IndexTuple;
typedef struct IndexAttributeBitMapData
{
bits8 bits[(INDEX_MAX_KEYS + 8 - 1) / 8];
} IndexAttributeBitMapData;
typedef IndexAttributeBitMapData * IndexAttributeBitMap;
/*
* t_info manipulation macros
*/
#define INDEX_SIZE_MASK 0x1FFF
#define INDEX_AM_RESERVED_BIT 0x2000 /* reserved for index-AM specific
* usage */
#define INDEX_VAR_MASK 0x4000
#define INDEX_NULL_MASK 0x8000
#define IndexTupleSize(itup) ((Size) ((itup)->t_info & INDEX_SIZE_MASK))
#define IndexTupleHasNulls(itup) ((((IndexTuple) (itup))->t_info & INDEX_NULL_MASK))
#define IndexTupleHasVarwidths(itup) ((((IndexTuple) (itup))->t_info & INDEX_VAR_MASK))
/* routines in indextuple.c */
extern IndexTuple index_form_tuple(TupleDesc tupleDescriptor,
Datum *values, bool *isnull);
extern IndexTuple index_form_tuple_context(TupleDesc tupleDescriptor,
Datum *values, bool *isnull,
MemoryContext context);
extern Datum nocache_index_getattr(IndexTuple tup, int attnum,
TupleDesc tupleDesc);
extern void index_deform_tuple(IndexTuple tup, TupleDesc tupleDescriptor,
Datum *values, bool *isnull);
extern void index_deform_tuple_internal(TupleDesc tupleDescriptor,
Datum *values, bool *isnull,
char *tp, bits8 *bp, int hasnulls);
extern IndexTuple CopyIndexTuple(IndexTuple source);
extern IndexTuple index_truncate_tuple(TupleDesc sourceDescriptor,
IndexTuple source, int leavenatts);
/*
* Takes an infomask as argument (primarily because this needs to be usable
* at index_form_tuple time so enough space is allocated).
*/
static inline Size
IndexInfoFindDataOffset(unsigned short t_info)
{
if (!(t_info & INDEX_NULL_MASK))
return MAXALIGN(sizeof(IndexTupleData));
else
return MAXALIGN(sizeof(IndexTupleData) + sizeof(IndexAttributeBitMapData));
}
#ifndef FRONTEND
/* ----------------
* index_getattr
*
* This gets called many times, so we macro the cacheable and NULL
* lookups, and call nocache_index_getattr() for the rest.
*
* ----------------
*/
static inline Datum
index_getattr(IndexTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull)
{
Assert(PointerIsValid(isnull));
Assert(attnum > 0);
*isnull = false;
if (!IndexTupleHasNulls(tup))
{
if (TupleDescAttr(tupleDesc, attnum - 1)->attcacheoff >= 0)
{
return fetchatt(TupleDescAttr(tupleDesc, attnum - 1),
(char *) tup + IndexInfoFindDataOffset(tup->t_info)
+ TupleDescAttr(tupleDesc, attnum - 1)->attcacheoff);
}
else
return nocache_index_getattr(tup, attnum, tupleDesc);
}
else
{
if (att_isnull(attnum - 1, (bits8 *) tup + sizeof(IndexTupleData)))
{
*isnull = true;
return (Datum) NULL;
}
else
return nocache_index_getattr(tup, attnum, tupleDesc);
}
}
#endif
/*
* MaxIndexTuplesPerPage is an upper bound on the number of tuples that can
* fit on one index page. An index tuple must have either data or a null
* bitmap, so we can safely assume it's at least 1 byte bigger than a bare
* IndexTupleData struct. We arrive at the divisor because each tuple
* must be maxaligned, and it must have an associated line pointer.
*
* To be index-type-independent, this does not account for any special space
* on the page, and is thus conservative.
*
* Note: in btree non-leaf pages, the first tuple has no key (it's implicitly
* minus infinity), thus breaking the "at least 1 byte bigger" assumption.
* On such a page, N tuples could take one MAXALIGN quantum less space than
* estimated here, seemingly allowing one more tuple than estimated here.
* But such a page always has at least MAXALIGN special space, so we're safe.
*/
#define MaxIndexTuplesPerPage \
((int) ((BLCKSZ - SizeOfPageHeaderData) / \
(MAXALIGN(sizeof(IndexTupleData) + 1) + sizeof(ItemIdData))))
#endif /* ITUP_H */