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/*-------------------------------------------------------------------------
*
* itup.h
* POSTGRES index tuple definitions.
*
*
* Portions Copyright (c) 1996-2020, 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))
/*
* Takes an infomask as argument (primarily because this needs to be usable
* at index_form_tuple time so enough space is allocated).
*/
#define IndexInfoFindDataOffset(t_info) \
( \
(!((t_info) & INDEX_NULL_MASK)) ? \
( \
(Size)MAXALIGN(sizeof(IndexTupleData)) \
) \
: \
( \
(Size)MAXALIGN(sizeof(IndexTupleData) + sizeof(IndexAttributeBitMapData)) \
) \
)
/* ----------------
* index_getattr
*
* This gets called many times, so we macro the cacheable and NULL
* lookups, and call nocache_index_getattr() for the rest.
*
* ----------------
*/
#define index_getattr(tup, attnum, tupleDesc, isnull) \
( \
AssertMacro(PointerIsValid(isnull) && (attnum) > 0), \
*(isnull) = false, \
!IndexTupleHasNulls(tup) ? \
( \
TupleDescAttr((tupleDesc), (attnum)-1)->attcacheoff >= 0 ? \
( \
fetchatt(TupleDescAttr((tupleDesc), (attnum)-1), \
(char *) (tup) + IndexInfoFindDataOffset((tup)->t_info) \
+ TupleDescAttr((tupleDesc), (attnum)-1)->attcacheoff) \
) \
: \
nocache_index_getattr((tup), (attnum), (tupleDesc)) \
) \
: \
( \
(att_isnull((attnum)-1, (char *)(tup) + sizeof(IndexTupleData))) ? \
( \
*(isnull) = true, \
(Datum)NULL \
) \
: \
( \
nocache_index_getattr((tup), (attnum), (tupleDesc)) \
) \
) \
)
/*
* 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))))
/* routines in indextuple.c */
extern IndexTuple index_form_tuple(TupleDesc tupleDescriptor,
Datum *values, bool *isnull);
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 IndexTuple CopyIndexTuple(IndexTuple source);
extern IndexTuple index_truncate_tuple(TupleDesc sourceDescriptor,
IndexTuple source, int leavenatts);
#endif /* ITUP_H */
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