162 lines
4.9 KiB
C
162 lines
4.9 KiB
C
/*-------------------------------------------------------------------------
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*
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* itup.h
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* POSTGRES index tuple definitions.
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*
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*
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* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/access/itup.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef ITUP_H
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#define ITUP_H
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#include "access/tupdesc.h"
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#include "access/tupmacs.h"
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#include "storage/bufpage.h"
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#include "storage/itemptr.h"
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/*
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* Index tuple header structure
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*
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* All index tuples start with IndexTupleData. If the HasNulls bit is set,
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* this is followed by an IndexAttributeBitMapData. The index attribute
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* values follow, beginning at a MAXALIGN boundary.
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*
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* Note that the space allocated for the bitmap does not vary with the number
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* of attributes; that is because we don't have room to store the number of
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* attributes in the header. Given the MAXALIGN constraint there's no space
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* savings to be had anyway, for usual values of INDEX_MAX_KEYS.
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*/
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typedef struct IndexTupleData
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{
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ItemPointerData t_tid; /* reference TID to heap tuple */
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/* ---------------
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* t_info is laid out in the following fashion:
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*
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* 15th (high) bit: has nulls
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* 14th bit: has var-width attributes
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* 13th bit: AM-defined meaning
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* 12-0 bit: size of tuple
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* ---------------
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*/
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unsigned short t_info; /* various info about tuple */
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} IndexTupleData; /* MORE DATA FOLLOWS AT END OF STRUCT */
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typedef IndexTupleData *IndexTuple;
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typedef struct IndexAttributeBitMapData
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{
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bits8 bits[(INDEX_MAX_KEYS + 8 - 1) / 8];
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} IndexAttributeBitMapData;
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typedef IndexAttributeBitMapData * IndexAttributeBitMap;
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/*
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* t_info manipulation macros
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*/
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#define INDEX_SIZE_MASK 0x1FFF
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#define INDEX_AM_RESERVED_BIT 0x2000 /* reserved for index-AM specific
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* usage */
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#define INDEX_VAR_MASK 0x4000
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#define INDEX_NULL_MASK 0x8000
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#define IndexTupleSize(itup) ((Size) ((itup)->t_info & INDEX_SIZE_MASK))
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#define IndexTupleHasNulls(itup) ((((IndexTuple) (itup))->t_info & INDEX_NULL_MASK))
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#define IndexTupleHasVarwidths(itup) ((((IndexTuple) (itup))->t_info & INDEX_VAR_MASK))
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/*
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* Takes an infomask as argument (primarily because this needs to be usable
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* at index_form_tuple time so enough space is allocated).
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*/
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#define IndexInfoFindDataOffset(t_info) \
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( \
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(!((t_info) & INDEX_NULL_MASK)) ? \
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( \
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(Size)MAXALIGN(sizeof(IndexTupleData)) \
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) \
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: \
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( \
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(Size)MAXALIGN(sizeof(IndexTupleData) + sizeof(IndexAttributeBitMapData)) \
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) \
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)
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/* ----------------
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* index_getattr
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*
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* This gets called many times, so we macro the cacheable and NULL
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* lookups, and call nocache_index_getattr() for the rest.
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*
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* ----------------
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*/
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#define index_getattr(tup, attnum, tupleDesc, isnull) \
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( \
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AssertMacro(PointerIsValid(isnull) && (attnum) > 0), \
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*(isnull) = false, \
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!IndexTupleHasNulls(tup) ? \
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( \
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TupleDescAttr((tupleDesc), (attnum)-1)->attcacheoff >= 0 ? \
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( \
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fetchatt(TupleDescAttr((tupleDesc), (attnum)-1), \
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(char *) (tup) + IndexInfoFindDataOffset((tup)->t_info) \
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+ TupleDescAttr((tupleDesc), (attnum)-1)->attcacheoff) \
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) \
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: \
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nocache_index_getattr((tup), (attnum), (tupleDesc)) \
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) \
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: \
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( \
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(att_isnull((attnum)-1, (char *)(tup) + sizeof(IndexTupleData))) ? \
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( \
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*(isnull) = true, \
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(Datum)NULL \
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) \
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: \
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( \
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nocache_index_getattr((tup), (attnum), (tupleDesc)) \
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) \
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) \
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)
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/*
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* MaxIndexTuplesPerPage is an upper bound on the number of tuples that can
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* fit on one index page. An index tuple must have either data or a null
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* bitmap, so we can safely assume it's at least 1 byte bigger than a bare
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* IndexTupleData struct. We arrive at the divisor because each tuple
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* must be maxaligned, and it must have an associated line pointer.
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*
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* To be index-type-independent, this does not account for any special space
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* on the page, and is thus conservative.
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*
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* Note: in btree non-leaf pages, the first tuple has no key (it's implicitly
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* minus infinity), thus breaking the "at least 1 byte bigger" assumption.
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* On such a page, N tuples could take one MAXALIGN quantum less space than
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* estimated here, seemingly allowing one more tuple than estimated here.
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* But such a page always has at least MAXALIGN special space, so we're safe.
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*/
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#define MaxIndexTuplesPerPage \
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((int) ((BLCKSZ - SizeOfPageHeaderData) / \
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(MAXALIGN(sizeof(IndexTupleData) + 1) + sizeof(ItemIdData))))
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/* routines in indextuple.c */
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extern IndexTuple index_form_tuple(TupleDesc tupleDescriptor,
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Datum *values, bool *isnull);
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extern Datum nocache_index_getattr(IndexTuple tup, int attnum,
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TupleDesc tupleDesc);
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extern void index_deform_tuple(IndexTuple tup, TupleDesc tupleDescriptor,
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Datum *values, bool *isnull);
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extern IndexTuple CopyIndexTuple(IndexTuple source);
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extern IndexTuple index_truncate_tuple(TupleDesc sourceDescriptor,
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IndexTuple source, int leavenatts);
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#endif /* ITUP_H */
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