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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 : } TupleConstr;
48 :
49 : /*
50 : * CompactAttribute
51 : * Cut-down version of FormData_pg_attribute for faster access for tasks
52 : * such as tuple deformation. The fields of this struct are populated
53 : * using the populate_compact_attribute() function, which must be called
54 : * directly after the FormData_pg_attribute struct is populated or
55 : * altered in any way.
56 : *
57 : * Currently, this struct is 16 bytes. Any code changes which enlarge this
58 : * struct should be considered very carefully.
59 : *
60 : * Code which must access a TupleDesc's attribute data should always make use
61 : * the fields of this struct when required fields are available here. It's
62 : * more efficient to access the memory in CompactAttribute due to it being a
63 : * more compact representation of FormData_pg_attribute and also because
64 : * accessing the FormData_pg_attribute requires an additional calculations to
65 : * obtain the base address of the array within the TupleDesc.
66 : */
67 : typedef struct CompactAttribute
68 : {
69 : int32 attcacheoff; /* fixed offset into tuple, if known, or -1 */
70 : int16 attlen; /* attr len in bytes or -1 = varlen, -2 =
71 : * cstring */
72 : bool attbyval; /* as FormData_pg_attribute.attbyval */
73 : bool attispackable; /* FormData_pg_attribute.attstorage !=
74 : * TYPSTORAGE_PLAIN */
75 : bool atthasmissing; /* as FormData_pg_attribute.atthasmissing */
76 : bool attisdropped; /* as FormData_pg_attribute.attisdropped */
77 : bool attgenerated; /* FormData_pg_attribute.attgenerated != '\0' */
78 : bool attnotnull; /* as FormData_pg_attribute.attnotnull */
79 : uint8 attalignby; /* alignment requirement in bytes */
80 : } CompactAttribute;
81 :
82 : /*
83 : * This struct is passed around within the backend to describe the structure
84 : * of tuples. For tuples coming from on-disk relations, the information is
85 : * collected from the pg_attribute, pg_attrdef, and pg_constraint catalogs.
86 : * Transient row types (such as the result of a join query) have anonymous
87 : * TupleDesc structs that generally omit any constraint info; therefore the
88 : * structure is designed to let the constraints be omitted efficiently.
89 : *
90 : * Note that only user attributes, not system attributes, are mentioned in
91 : * TupleDesc.
92 : *
93 : * If the tupdesc is known to correspond to a named rowtype (such as a table's
94 : * rowtype) then tdtypeid identifies that type and tdtypmod is -1. Otherwise
95 : * tdtypeid is RECORDOID, and tdtypmod can be either -1 for a fully anonymous
96 : * row type, or a value >= 0 to allow the rowtype to be looked up in the
97 : * typcache.c type cache.
98 : *
99 : * Note that tdtypeid is never the OID of a domain over composite, even if
100 : * we are dealing with values that are known (at some higher level) to be of
101 : * a domain-over-composite type. This is because tdtypeid/tdtypmod need to
102 : * match up with the type labeling of composite Datums, and those are never
103 : * explicitly marked as being of a domain type, either.
104 : *
105 : * Tuple descriptors that live in caches (relcache or typcache, at present)
106 : * are reference-counted: they can be deleted when their reference count goes
107 : * to zero. Tuple descriptors created by the executor need no reference
108 : * counting, however: they are simply created in the appropriate memory
109 : * context and go away when the context is freed. We set the tdrefcount
110 : * field of such a descriptor to -1, while reference-counted descriptors
111 : * always have tdrefcount >= 0.
112 : *
113 : * Beyond the compact_attrs variable length array, the TupleDesc stores an
114 : * array of FormData_pg_attribute. The TupleDescAttr() function, as defined
115 : * below, takes care of calculating the address of the elements of the
116 : * FormData_pg_attribute array.
117 : *
118 : * The array of CompactAttribute is effectively an abbreviated version of the
119 : * array of FormData_pg_attribute. Because CompactAttribute is significantly
120 : * smaller than FormData_pg_attribute, code, especially performance-critical
121 : * code, should prioritize using the fields from the CompactAttribute over the
122 : * equivalent fields in FormData_pg_attribute.
123 : *
124 : * Any code making changes manually to and fields in the FormData_pg_attribute
125 : * array must subsequently call populate_compact_attribute() to flush the
126 : * changes out to the corresponding 'compact_attrs' element.
127 : */
128 : typedef struct TupleDescData
129 : {
130 : int natts; /* number of attributes in the tuple */
131 : Oid tdtypeid; /* composite type ID for tuple type */
132 : int32 tdtypmod; /* typmod for tuple type */
133 : int tdrefcount; /* reference count, or -1 if not counting */
134 : TupleConstr *constr; /* constraints, or NULL if none */
135 : /* compact_attrs[N] is the compact metadata of Attribute Number N+1 */
136 : CompactAttribute compact_attrs[FLEXIBLE_ARRAY_MEMBER];
137 : } TupleDescData;
138 : typedef struct TupleDescData *TupleDesc;
139 :
140 : extern void populate_compact_attribute(TupleDesc tupdesc, int attnum);
141 :
142 : /*
143 : * Calculates the base address of the Form_pg_attribute at the end of the
144 : * TupleDescData struct.
145 : */
146 : #define TupleDescAttrAddress(desc) \
147 : (Form_pg_attribute) ((char *) (desc) + \
148 : (offsetof(struct TupleDescData, compact_attrs) + \
149 : (desc)->natts * sizeof(CompactAttribute)))
150 :
151 : /* Accessor for the i'th FormData_pg_attribute element of tupdesc. */
152 : static inline FormData_pg_attribute *
153 287484524 : TupleDescAttr(TupleDesc tupdesc, int i)
154 : {
155 287484524 : FormData_pg_attribute *attrs = TupleDescAttrAddress(tupdesc);
156 :
157 287484524 : return &attrs[i];
158 : }
159 :
160 : #undef TupleDescAttrAddress
161 :
162 : extern void verify_compact_attribute(TupleDesc, int attnum);
163 :
164 : /*
165 : * Accessor for the i'th CompactAttribute element of tupdesc.
166 : */
167 : static inline CompactAttribute *
168 2503186368 : TupleDescCompactAttr(TupleDesc tupdesc, int i)
169 : {
170 2503186368 : CompactAttribute *cattr = &tupdesc->compact_attrs[i];
171 :
172 : #ifdef USE_ASSERT_CHECKING
173 :
174 : /* Check that the CompactAttribute is correctly populated */
175 : verify_compact_attribute(tupdesc, i);
176 : #endif
177 :
178 2503186368 : return cattr;
179 : }
180 :
181 : extern TupleDesc CreateTemplateTupleDesc(int natts);
182 :
183 : extern TupleDesc CreateTupleDesc(int natts, Form_pg_attribute *attrs);
184 :
185 : extern TupleDesc CreateTupleDescCopy(TupleDesc tupdesc);
186 :
187 : extern TupleDesc CreateTupleDescTruncatedCopy(TupleDesc tupdesc, int natts);
188 :
189 : extern TupleDesc CreateTupleDescCopyConstr(TupleDesc tupdesc);
190 :
191 : #define TupleDescSize(src) \
192 : (offsetof(struct TupleDescData, compact_attrs) + \
193 : (src)->natts * sizeof(CompactAttribute) + \
194 : (src)->natts * sizeof(FormData_pg_attribute))
195 :
196 : extern void TupleDescCopy(TupleDesc dst, TupleDesc src);
197 :
198 : extern void TupleDescCopyEntry(TupleDesc dst, AttrNumber dstAttno,
199 : TupleDesc src, AttrNumber srcAttno);
200 :
201 : extern void FreeTupleDesc(TupleDesc tupdesc);
202 :
203 : extern void IncrTupleDescRefCount(TupleDesc tupdesc);
204 : extern void DecrTupleDescRefCount(TupleDesc tupdesc);
205 :
206 : #define PinTupleDesc(tupdesc) \
207 : do { \
208 : if ((tupdesc)->tdrefcount >= 0) \
209 : IncrTupleDescRefCount(tupdesc); \
210 : } while (0)
211 :
212 : #define ReleaseTupleDesc(tupdesc) \
213 : do { \
214 : if ((tupdesc)->tdrefcount >= 0) \
215 : DecrTupleDescRefCount(tupdesc); \
216 : } while (0)
217 :
218 : extern bool equalTupleDescs(TupleDesc tupdesc1, TupleDesc tupdesc2);
219 : extern bool equalRowTypes(TupleDesc tupdesc1, TupleDesc tupdesc2);
220 : extern uint32 hashRowType(TupleDesc desc);
221 :
222 : extern void TupleDescInitEntry(TupleDesc desc,
223 : AttrNumber attributeNumber,
224 : const char *attributeName,
225 : Oid oidtypeid,
226 : int32 typmod,
227 : int attdim);
228 :
229 : extern void TupleDescInitBuiltinEntry(TupleDesc desc,
230 : AttrNumber attributeNumber,
231 : const char *attributeName,
232 : Oid oidtypeid,
233 : int32 typmod,
234 : int attdim);
235 :
236 : extern void TupleDescInitEntryCollation(TupleDesc desc,
237 : AttrNumber attributeNumber,
238 : Oid collationid);
239 :
240 : extern TupleDesc BuildDescFromLists(const List *names, const List *types, const List *typmods, const List *collations);
241 :
242 : extern Node *TupleDescGetDefault(TupleDesc tupdesc, AttrNumber attnum);
243 :
244 : #endif /* TUPDESC_H */
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