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1 : /*-------------------------------------------------------------------------
2 : *
3 : * itup.h
4 : * POSTGRES index tuple definitions.
5 : *
6 : *
7 : * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
8 : * Portions Copyright (c) 1994, Regents of the University of California
9 : *
10 : * src/include/access/itup.h
11 : *
12 : *-------------------------------------------------------------------------
13 : */
14 : #ifndef ITUP_H
15 : #define ITUP_H
16 :
17 : #include "access/tupdesc.h"
18 : #include "access/tupmacs.h"
19 : #include "storage/bufpage.h"
20 : #include "storage/itemptr.h"
21 :
22 : /*
23 : * Index tuple header structure
24 : *
25 : * All index tuples start with IndexTupleData. If the HasNulls bit is set,
26 : * this is followed by an IndexAttributeBitMapData. The index attribute
27 : * values follow, beginning at a MAXALIGN boundary.
28 : *
29 : * Note that the space allocated for the bitmap does not vary with the number
30 : * of attributes; that is because we don't have room to store the number of
31 : * attributes in the header. Given the MAXALIGN constraint there's no space
32 : * savings to be had anyway, for usual values of INDEX_MAX_KEYS.
33 : */
34 :
35 : typedef struct IndexTupleData
36 : {
37 : ItemPointerData t_tid; /* reference TID to heap tuple */
38 :
39 : /* ---------------
40 : * t_info is laid out in the following fashion:
41 : *
42 : * 15th (high) bit: has nulls
43 : * 14th bit: has var-width attributes
44 : * 13th bit: AM-defined meaning
45 : * 12-0 bit: size of tuple
46 : * ---------------
47 : */
48 :
49 : unsigned short t_info; /* various info about tuple */
50 :
51 : } IndexTupleData; /* MORE DATA FOLLOWS AT END OF STRUCT */
52 :
53 : typedef IndexTupleData *IndexTuple;
54 :
55 : typedef struct IndexAttributeBitMapData
56 : {
57 : bits8 bits[(INDEX_MAX_KEYS + 8 - 1) / 8];
58 : } IndexAttributeBitMapData;
59 :
60 : typedef IndexAttributeBitMapData * IndexAttributeBitMap;
61 :
62 : /*
63 : * t_info manipulation macros
64 : */
65 : #define INDEX_SIZE_MASK 0x1FFF
66 : #define INDEX_AM_RESERVED_BIT 0x2000 /* reserved for index-AM specific
67 : * usage */
68 : #define INDEX_VAR_MASK 0x4000
69 : #define INDEX_NULL_MASK 0x8000
70 :
71 : #define IndexTupleSize(itup) ((Size) ((itup)->t_info & INDEX_SIZE_MASK))
72 : #define IndexTupleHasNulls(itup) ((((IndexTuple) (itup))->t_info & INDEX_NULL_MASK))
73 : #define IndexTupleHasVarwidths(itup) ((((IndexTuple) (itup))->t_info & INDEX_VAR_MASK))
74 :
75 :
76 : /* routines in indextuple.c */
77 : extern IndexTuple index_form_tuple(TupleDesc tupleDescriptor,
78 : const Datum *values, const bool *isnull);
79 : extern IndexTuple index_form_tuple_context(TupleDesc tupleDescriptor,
80 : const Datum *values, const bool *isnull,
81 : MemoryContext context);
82 : extern Datum nocache_index_getattr(IndexTuple tup, int attnum,
83 : TupleDesc tupleDesc);
84 : extern void index_deform_tuple(IndexTuple tup, TupleDesc tupleDescriptor,
85 : Datum *values, bool *isnull);
86 : extern void index_deform_tuple_internal(TupleDesc tupleDescriptor,
87 : Datum *values, bool *isnull,
88 : char *tp, bits8 *bp, int hasnulls);
89 : extern IndexTuple CopyIndexTuple(IndexTuple source);
90 : extern IndexTuple index_truncate_tuple(TupleDesc sourceDescriptor,
91 : IndexTuple source, int leavenatts);
92 :
93 :
94 : /*
95 : * Takes an infomask as argument (primarily because this needs to be usable
96 : * at index_form_tuple time so enough space is allocated).
97 : */
98 : static inline Size
99 493301030 : IndexInfoFindDataOffset(unsigned short t_info)
100 : {
101 493301030 : if (!(t_info & INDEX_NULL_MASK))
102 493078936 : return MAXALIGN(sizeof(IndexTupleData));
103 : else
104 222094 : return MAXALIGN(sizeof(IndexTupleData) + sizeof(IndexAttributeBitMapData));
105 : }
106 :
107 : #ifndef FRONTEND
108 :
109 : /* ----------------
110 : * index_getattr
111 : *
112 : * This gets called many times, so we macro the cacheable and NULL
113 : * lookups, and call nocache_index_getattr() for the rest.
114 : *
115 : * ----------------
116 : */
117 : static inline Datum
118 459723264 : index_getattr(IndexTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull)
119 : {
120 : Assert(PointerIsValid(isnull));
121 : Assert(attnum > 0);
122 :
123 459723264 : *isnull = false;
124 :
125 459723264 : if (!IndexTupleHasNulls(tup))
126 : {
127 458992070 : if (TupleDescAttr(tupleDesc, attnum - 1)->attcacheoff >= 0)
128 : {
129 453515066 : return fetchatt(TupleDescAttr(tupleDesc, attnum - 1),
130 : (char *) tup + IndexInfoFindDataOffset(tup->t_info)
131 : + TupleDescAttr(tupleDesc, attnum - 1)->attcacheoff);
132 : }
133 : else
134 5477004 : return nocache_index_getattr(tup, attnum, tupleDesc);
135 : }
136 : else
137 : {
138 731194 : if (att_isnull(attnum - 1, (bits8 *) tup + sizeof(IndexTupleData)))
139 : {
140 618284 : *isnull = true;
141 618284 : return (Datum) NULL;
142 : }
143 : else
144 112910 : return nocache_index_getattr(tup, attnum, tupleDesc);
145 : }
146 : }
147 :
148 : #endif
149 :
150 : /*
151 : * MaxIndexTuplesPerPage is an upper bound on the number of tuples that can
152 : * fit on one index page. An index tuple must have either data or a null
153 : * bitmap, so we can safely assume it's at least 1 byte bigger than a bare
154 : * IndexTupleData struct. We arrive at the divisor because each tuple
155 : * must be maxaligned, and it must have an associated line pointer.
156 : *
157 : * To be index-type-independent, this does not account for any special space
158 : * on the page, and is thus conservative.
159 : *
160 : * Note: in btree non-leaf pages, the first tuple has no key (it's implicitly
161 : * minus infinity), thus breaking the "at least 1 byte bigger" assumption.
162 : * On such a page, N tuples could take one MAXALIGN quantum less space than
163 : * estimated here, seemingly allowing one more tuple than estimated here.
164 : * But such a page always has at least MAXALIGN special space, so we're safe.
165 : */
166 : #define MaxIndexTuplesPerPage \
167 : ((int) ((BLCKSZ - SizeOfPageHeaderData) / \
168 : (MAXALIGN(sizeof(IndexTupleData) + 1) + sizeof(ItemIdData))))
169 :
170 : #endif /* ITUP_H */
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