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1 : /*-------------------------------------------------------------------------
2 : *
3 : * tupdesc.h
4 : * POSTGRES tuple descriptor definitions.
5 : *
6 : *
7 : * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
8 : * Portions Copyright (c) 1994, Regents of the University of California
9 : *
10 : * src/include/access/tupdesc.h
11 : *
12 : *-------------------------------------------------------------------------
13 : */
14 : #ifndef TUPDESC_H
15 : #define TUPDESC_H
16 :
17 : #include "access/attnum.h"
18 : #include "catalog/pg_attribute.h"
19 : #include "nodes/pg_list.h"
20 :
21 :
22 : typedef struct AttrDefault
23 : {
24 : AttrNumber adnum;
25 : char *adbin; /* nodeToString representation of expr */
26 : } AttrDefault;
27 :
28 : typedef struct ConstrCheck
29 : {
30 : char *ccname;
31 : char *ccbin; /* nodeToString representation of expr */
32 : bool ccenforced;
33 : bool ccvalid;
34 : bool ccnoinherit; /* this is a non-inheritable constraint */
35 : } ConstrCheck;
36 :
37 : /* This structure contains constraints of a tuple */
38 : typedef struct TupleConstr
39 : {
40 : AttrDefault *defval; /* array */
41 : ConstrCheck *check; /* array */
42 : struct AttrMissing *missing; /* missing attributes values, NULL if none */
43 : uint16 num_defval;
44 : uint16 num_check;
45 : bool has_not_null;
46 : bool has_generated_stored;
47 : bool has_generated_virtual;
48 : } TupleConstr;
49 :
50 : /*
51 : * CompactAttribute
52 : * Cut-down version of FormData_pg_attribute for faster access for tasks
53 : * such as tuple deformation. The fields of this struct are populated
54 : * using the populate_compact_attribute() function, which must be called
55 : * directly after the FormData_pg_attribute struct is populated or
56 : * altered in any way.
57 : *
58 : * Currently, this struct is 16 bytes. Any code changes which enlarge this
59 : * struct should be considered very carefully.
60 : *
61 : * Code which must access a TupleDesc's attribute data should always make use
62 : * the fields of this struct when required fields are available here. It's
63 : * more efficient to access the memory in CompactAttribute due to it being a
64 : * more compact representation of FormData_pg_attribute and also because
65 : * accessing the FormData_pg_attribute requires an additional calculations to
66 : * obtain the base address of the array within the TupleDesc.
67 : */
68 : typedef struct CompactAttribute
69 : {
70 : int32 attcacheoff; /* fixed offset into tuple, if known, or -1 */
71 : int16 attlen; /* attr len in bytes or -1 = varlen, -2 =
72 : * cstring */
73 : bool attbyval; /* as FormData_pg_attribute.attbyval */
74 : bool attispackable; /* FormData_pg_attribute.attstorage !=
75 : * TYPSTORAGE_PLAIN */
76 : bool atthasmissing; /* as FormData_pg_attribute.atthasmissing */
77 : bool attisdropped; /* as FormData_pg_attribute.attisdropped */
78 : bool attgenerated; /* FormData_pg_attribute.attgenerated != '\0' */
79 : bool attnotnull; /* as FormData_pg_attribute.attnotnull */
80 : uint8 attalignby; /* alignment requirement in bytes */
81 : } CompactAttribute;
82 :
83 : /*
84 : * This struct is passed around within the backend to describe the structure
85 : * of tuples. For tuples coming from on-disk relations, the information is
86 : * collected from the pg_attribute, pg_attrdef, and pg_constraint catalogs.
87 : * Transient row types (such as the result of a join query) have anonymous
88 : * TupleDesc structs that generally omit any constraint info; therefore the
89 : * structure is designed to let the constraints be omitted efficiently.
90 : *
91 : * Note that only user attributes, not system attributes, are mentioned in
92 : * TupleDesc.
93 : *
94 : * If the tupdesc is known to correspond to a named rowtype (such as a table's
95 : * rowtype) then tdtypeid identifies that type and tdtypmod is -1. Otherwise
96 : * tdtypeid is RECORDOID, and tdtypmod can be either -1 for a fully anonymous
97 : * row type, or a value >= 0 to allow the rowtype to be looked up in the
98 : * typcache.c type cache.
99 : *
100 : * Note that tdtypeid is never the OID of a domain over composite, even if
101 : * we are dealing with values that are known (at some higher level) to be of
102 : * a domain-over-composite type. This is because tdtypeid/tdtypmod need to
103 : * match up with the type labeling of composite Datums, and those are never
104 : * explicitly marked as being of a domain type, either.
105 : *
106 : * Tuple descriptors that live in caches (relcache or typcache, at present)
107 : * are reference-counted: they can be deleted when their reference count goes
108 : * to zero. Tuple descriptors created by the executor need no reference
109 : * counting, however: they are simply created in the appropriate memory
110 : * context and go away when the context is freed. We set the tdrefcount
111 : * field of such a descriptor to -1, while reference-counted descriptors
112 : * always have tdrefcount >= 0.
113 : *
114 : * Beyond the compact_attrs variable length array, the TupleDesc stores an
115 : * array of FormData_pg_attribute. The TupleDescAttr() function, as defined
116 : * below, takes care of calculating the address of the elements of the
117 : * FormData_pg_attribute array.
118 : *
119 : * The array of CompactAttribute is effectively an abbreviated version of the
120 : * array of FormData_pg_attribute. Because CompactAttribute is significantly
121 : * smaller than FormData_pg_attribute, code, especially performance-critical
122 : * code, should prioritize using the fields from the CompactAttribute over the
123 : * equivalent fields in FormData_pg_attribute.
124 : *
125 : * Any code making changes manually to and fields in the FormData_pg_attribute
126 : * array must subsequently call populate_compact_attribute() to flush the
127 : * changes out to the corresponding 'compact_attrs' element.
128 : */
129 : typedef struct TupleDescData
130 : {
131 : int natts; /* number of attributes in the tuple */
132 : Oid tdtypeid; /* composite type ID for tuple type */
133 : int32 tdtypmod; /* typmod for tuple type */
134 : int tdrefcount; /* reference count, or -1 if not counting */
135 : TupleConstr *constr; /* constraints, or NULL if none */
136 : /* compact_attrs[N] is the compact metadata of Attribute Number N+1 */
137 : CompactAttribute compact_attrs[FLEXIBLE_ARRAY_MEMBER];
138 : } TupleDescData;
139 : typedef struct TupleDescData *TupleDesc;
140 :
141 : extern void populate_compact_attribute(TupleDesc tupdesc, int attnum);
142 :
143 : /*
144 : * Calculates the base address of the Form_pg_attribute at the end of the
145 : * TupleDescData struct.
146 : */
147 : #define TupleDescAttrAddress(desc) \
148 : (Form_pg_attribute) ((char *) (desc) + \
149 : (offsetof(struct TupleDescData, compact_attrs) + \
150 : (desc)->natts * sizeof(CompactAttribute)))
151 :
152 : /* Accessor for the i'th FormData_pg_attribute element of tupdesc. */
153 : static inline FormData_pg_attribute *
154 305009388 : TupleDescAttr(TupleDesc tupdesc, int i)
155 : {
156 305009388 : FormData_pg_attribute *attrs = TupleDescAttrAddress(tupdesc);
157 :
158 305009388 : return &attrs[i];
159 : }
160 :
161 : #undef TupleDescAttrAddress
162 :
163 : extern void verify_compact_attribute(TupleDesc, int attnum);
164 :
165 : /*
166 : * Accessor for the i'th CompactAttribute element of tupdesc.
167 : */
168 : static inline CompactAttribute *
169 2695444536 : TupleDescCompactAttr(TupleDesc tupdesc, int i)
170 : {
171 2695444536 : CompactAttribute *cattr = &tupdesc->compact_attrs[i];
172 :
173 : #ifdef USE_ASSERT_CHECKING
174 :
175 : /* Check that the CompactAttribute is correctly populated */
176 : verify_compact_attribute(tupdesc, i);
177 : #endif
178 :
179 2695444536 : return cattr;
180 : }
181 :
182 : extern TupleDesc CreateTemplateTupleDesc(int natts);
183 :
184 : extern TupleDesc CreateTupleDesc(int natts, Form_pg_attribute *attrs);
185 :
186 : extern TupleDesc CreateTupleDescCopy(TupleDesc tupdesc);
187 :
188 : extern TupleDesc CreateTupleDescTruncatedCopy(TupleDesc tupdesc, int natts);
189 :
190 : extern TupleDesc CreateTupleDescCopyConstr(TupleDesc tupdesc);
191 :
192 : #define TupleDescSize(src) \
193 : (offsetof(struct TupleDescData, compact_attrs) + \
194 : (src)->natts * sizeof(CompactAttribute) + \
195 : (src)->natts * sizeof(FormData_pg_attribute))
196 :
197 : extern void TupleDescCopy(TupleDesc dst, TupleDesc src);
198 :
199 : extern void TupleDescCopyEntry(TupleDesc dst, AttrNumber dstAttno,
200 : TupleDesc src, AttrNumber srcAttno);
201 :
202 : extern void FreeTupleDesc(TupleDesc tupdesc);
203 :
204 : extern void IncrTupleDescRefCount(TupleDesc tupdesc);
205 : extern void DecrTupleDescRefCount(TupleDesc tupdesc);
206 :
207 : #define PinTupleDesc(tupdesc) \
208 : do { \
209 : if ((tupdesc)->tdrefcount >= 0) \
210 : IncrTupleDescRefCount(tupdesc); \
211 : } while (0)
212 :
213 : #define ReleaseTupleDesc(tupdesc) \
214 : do { \
215 : if ((tupdesc)->tdrefcount >= 0) \
216 : DecrTupleDescRefCount(tupdesc); \
217 : } while (0)
218 :
219 : extern bool equalTupleDescs(TupleDesc tupdesc1, TupleDesc tupdesc2);
220 : extern bool equalRowTypes(TupleDesc tupdesc1, TupleDesc tupdesc2);
221 : extern uint32 hashRowType(TupleDesc desc);
222 :
223 : extern void TupleDescInitEntry(TupleDesc desc,
224 : AttrNumber attributeNumber,
225 : const char *attributeName,
226 : Oid oidtypeid,
227 : int32 typmod,
228 : int attdim);
229 :
230 : extern void TupleDescInitBuiltinEntry(TupleDesc desc,
231 : AttrNumber attributeNumber,
232 : const char *attributeName,
233 : Oid oidtypeid,
234 : int32 typmod,
235 : int attdim);
236 :
237 : extern void TupleDescInitEntryCollation(TupleDesc desc,
238 : AttrNumber attributeNumber,
239 : Oid collationid);
240 :
241 : extern TupleDesc BuildDescFromLists(const List *names, const List *types, const List *typmods, const List *collations);
242 :
243 : extern Node *TupleDescGetDefault(TupleDesc tupdesc, AttrNumber attnum);
244 :
245 : #endif /* TUPDESC_H */
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