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/*------------------------------------------------------------------------- * * itup.h * POSTGRES index tuple definitions. * * * Portions Copyright (c) 1996-2012, 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: unused * 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 /* bit 0x2000 is not used at present */ #define INDEX_VAR_MASK 0x4000 #define INDEX_NULL_MASK 0x8000 #define IndexTupleSize(itup) ((Size) (((IndexTuple) (itup))->t_info & INDEX_SIZE_MASK)) #define IndexTupleDSize(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) ? \ ( \ (tupleDesc)->attrs[(attnum)-1]->attcacheoff >= 0 ? \ ( \ fetchatt((tupleDesc)->attrs[(attnum)-1], \ (char *) (tup) + IndexInfoFindDataOffset((tup)->t_info) \ + (tupleDesc)->attrs[(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 item pointer. */ #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); #endif /* ITUP_H */