Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * pg_attrdef.c
4 : * routines to support manipulation of the pg_attrdef relation
5 : *
6 : * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
7 : * Portions Copyright (c) 1994, Regents of the University of California
8 : *
9 : *
10 : * IDENTIFICATION
11 : * src/backend/catalog/pg_attrdef.c
12 : *
13 : *-------------------------------------------------------------------------
14 : */
15 : #include "postgres.h"
16 :
17 : #include "access/relation.h"
18 : #include "access/table.h"
19 : #include "catalog/dependency.h"
20 : #include "catalog/indexing.h"
21 : #include "catalog/objectaccess.h"
22 : #include "catalog/pg_attrdef.h"
23 : #include "utils/builtins.h"
24 : #include "utils/fmgroids.h"
25 : #include "utils/rel.h"
26 : #include "utils/syscache.h"
27 :
28 :
29 : /*
30 : * Store a default expression for column attnum of relation rel.
31 : *
32 : * Returns the OID of the new pg_attrdef tuple.
33 : */
34 : Oid
35 4718 : StoreAttrDefault(Relation rel, AttrNumber attnum,
36 : Node *expr, bool is_internal)
37 : {
38 : char *adbin;
39 : Relation adrel;
40 : HeapTuple tuple;
41 : Datum values[Natts_pg_attrdef];
42 : static bool nulls[Natts_pg_attrdef] = {false, false, false, false};
43 : Relation attrrel;
44 : HeapTuple atttup;
45 : Form_pg_attribute attStruct;
46 4718 : Datum valuesAtt[Natts_pg_attribute] = {0};
47 4718 : bool nullsAtt[Natts_pg_attribute] = {0};
48 4718 : bool replacesAtt[Natts_pg_attribute] = {0};
49 : char attgenerated;
50 : Oid attrdefOid;
51 : ObjectAddress colobject,
52 : defobject;
53 :
54 4718 : adrel = table_open(AttrDefaultRelationId, RowExclusiveLock);
55 :
56 : /*
57 : * Flatten expression to string form for storage.
58 : */
59 4718 : adbin = nodeToString(expr);
60 :
61 : /*
62 : * Make the pg_attrdef entry.
63 : */
64 4718 : attrdefOid = GetNewOidWithIndex(adrel, AttrDefaultOidIndexId,
65 : Anum_pg_attrdef_oid);
66 4718 : values[Anum_pg_attrdef_oid - 1] = ObjectIdGetDatum(attrdefOid);
67 4718 : values[Anum_pg_attrdef_adrelid - 1] = ObjectIdGetDatum(RelationGetRelid(rel));
68 4718 : values[Anum_pg_attrdef_adnum - 1] = Int16GetDatum(attnum);
69 4718 : values[Anum_pg_attrdef_adbin - 1] = CStringGetTextDatum(adbin);
70 :
71 4718 : tuple = heap_form_tuple(adrel->rd_att, values, nulls);
72 4718 : CatalogTupleInsert(adrel, tuple);
73 :
74 4718 : defobject.classId = AttrDefaultRelationId;
75 4718 : defobject.objectId = attrdefOid;
76 4718 : defobject.objectSubId = 0;
77 :
78 4718 : table_close(adrel, RowExclusiveLock);
79 :
80 : /* now can free some of the stuff allocated above */
81 4718 : pfree(DatumGetPointer(values[Anum_pg_attrdef_adbin - 1]));
82 4718 : heap_freetuple(tuple);
83 4718 : pfree(adbin);
84 :
85 : /*
86 : * Update the pg_attribute entry for the column to show that a default
87 : * exists.
88 : */
89 4718 : attrrel = table_open(AttributeRelationId, RowExclusiveLock);
90 4718 : atttup = SearchSysCacheCopy2(ATTNUM,
91 : ObjectIdGetDatum(RelationGetRelid(rel)),
92 : Int16GetDatum(attnum));
93 4718 : if (!HeapTupleIsValid(atttup))
94 0 : elog(ERROR, "cache lookup failed for attribute %d of relation %u",
95 : attnum, RelationGetRelid(rel));
96 4718 : attStruct = (Form_pg_attribute) GETSTRUCT(atttup);
97 4718 : attgenerated = attStruct->attgenerated;
98 :
99 4718 : valuesAtt[Anum_pg_attribute_atthasdef - 1] = BoolGetDatum(true);
100 4718 : replacesAtt[Anum_pg_attribute_atthasdef - 1] = true;
101 :
102 4718 : atttup = heap_modify_tuple(atttup, RelationGetDescr(attrrel),
103 : valuesAtt, nullsAtt, replacesAtt);
104 :
105 4718 : CatalogTupleUpdate(attrrel, &atttup->t_self, atttup);
106 :
107 4718 : table_close(attrrel, RowExclusiveLock);
108 4718 : heap_freetuple(atttup);
109 :
110 : /*
111 : * Make a dependency so that the pg_attrdef entry goes away if the column
112 : * (or whole table) is deleted. In the case of a generated column, make
113 : * it an internal dependency to prevent the default expression from being
114 : * deleted separately.
115 : */
116 4718 : colobject.classId = RelationRelationId;
117 4718 : colobject.objectId = RelationGetRelid(rel);
118 4718 : colobject.objectSubId = attnum;
119 :
120 4718 : recordDependencyOn(&defobject, &colobject,
121 : attgenerated ? DEPENDENCY_INTERNAL : DEPENDENCY_AUTO);
122 :
123 : /*
124 : * Record dependencies on objects used in the expression, too.
125 : */
126 4718 : recordDependencyOnSingleRelExpr(&defobject, expr, RelationGetRelid(rel),
127 : DEPENDENCY_NORMAL,
128 : DEPENDENCY_NORMAL, false);
129 :
130 : /*
131 : * Post creation hook for attribute defaults.
132 : *
133 : * XXX. ALTER TABLE ALTER COLUMN SET/DROP DEFAULT is implemented with a
134 : * couple of deletion/creation of the attribute's default entry, so the
135 : * callee should check existence of an older version of this entry if it
136 : * needs to distinguish.
137 : */
138 4718 : InvokeObjectPostCreateHookArg(AttrDefaultRelationId,
139 : RelationGetRelid(rel), attnum, is_internal);
140 :
141 4718 : return attrdefOid;
142 : }
143 :
144 :
145 : /*
146 : * RemoveAttrDefault
147 : *
148 : * If the specified relation/attribute has a default, remove it.
149 : * (If no default, raise error if complain is true, else return quietly.)
150 : */
151 : void
152 860 : RemoveAttrDefault(Oid relid, AttrNumber attnum,
153 : DropBehavior behavior, bool complain, bool internal)
154 : {
155 : Relation attrdef_rel;
156 : ScanKeyData scankeys[2];
157 : SysScanDesc scan;
158 : HeapTuple tuple;
159 860 : bool found = false;
160 :
161 860 : attrdef_rel = table_open(AttrDefaultRelationId, RowExclusiveLock);
162 :
163 860 : ScanKeyInit(&scankeys[0],
164 : Anum_pg_attrdef_adrelid,
165 : BTEqualStrategyNumber, F_OIDEQ,
166 : ObjectIdGetDatum(relid));
167 860 : ScanKeyInit(&scankeys[1],
168 : Anum_pg_attrdef_adnum,
169 : BTEqualStrategyNumber, F_INT2EQ,
170 : Int16GetDatum(attnum));
171 :
172 860 : scan = systable_beginscan(attrdef_rel, AttrDefaultIndexId, true,
173 : NULL, 2, scankeys);
174 :
175 : /* There should be at most one matching tuple, but we loop anyway */
176 1440 : while (HeapTupleIsValid(tuple = systable_getnext(scan)))
177 : {
178 : ObjectAddress object;
179 580 : Form_pg_attrdef attrtuple = (Form_pg_attrdef) GETSTRUCT(tuple);
180 :
181 580 : object.classId = AttrDefaultRelationId;
182 580 : object.objectId = attrtuple->oid;
183 580 : object.objectSubId = 0;
184 :
185 580 : performDeletion(&object, behavior,
186 : internal ? PERFORM_DELETION_INTERNAL : 0);
187 :
188 580 : found = true;
189 : }
190 :
191 860 : systable_endscan(scan);
192 860 : table_close(attrdef_rel, RowExclusiveLock);
193 :
194 860 : if (complain && !found)
195 0 : elog(ERROR, "could not find attrdef tuple for relation %u attnum %d",
196 : relid, attnum);
197 860 : }
198 :
199 : /*
200 : * RemoveAttrDefaultById
201 : *
202 : * Remove a pg_attrdef entry specified by OID. This is the guts of
203 : * attribute-default removal. Note it should be called via performDeletion,
204 : * not directly.
205 : */
206 : void
207 3254 : RemoveAttrDefaultById(Oid attrdefId)
208 : {
209 : Relation attrdef_rel;
210 : Relation attr_rel;
211 : Relation myrel;
212 : ScanKeyData scankeys[1];
213 : SysScanDesc scan;
214 : HeapTuple tuple;
215 : Oid myrelid;
216 : AttrNumber myattnum;
217 :
218 : /* Grab an appropriate lock on the pg_attrdef relation */
219 3254 : attrdef_rel = table_open(AttrDefaultRelationId, RowExclusiveLock);
220 :
221 : /* Find the pg_attrdef tuple */
222 3254 : ScanKeyInit(&scankeys[0],
223 : Anum_pg_attrdef_oid,
224 : BTEqualStrategyNumber, F_OIDEQ,
225 : ObjectIdGetDatum(attrdefId));
226 :
227 3254 : scan = systable_beginscan(attrdef_rel, AttrDefaultOidIndexId, true,
228 : NULL, 1, scankeys);
229 :
230 3254 : tuple = systable_getnext(scan);
231 3254 : if (!HeapTupleIsValid(tuple))
232 0 : elog(ERROR, "could not find tuple for attrdef %u", attrdefId);
233 :
234 3254 : myrelid = ((Form_pg_attrdef) GETSTRUCT(tuple))->adrelid;
235 3254 : myattnum = ((Form_pg_attrdef) GETSTRUCT(tuple))->adnum;
236 :
237 : /* Get an exclusive lock on the relation owning the attribute */
238 3254 : myrel = relation_open(myrelid, AccessExclusiveLock);
239 :
240 : /* Now we can delete the pg_attrdef row */
241 3254 : CatalogTupleDelete(attrdef_rel, &tuple->t_self);
242 :
243 3254 : systable_endscan(scan);
244 3254 : table_close(attrdef_rel, RowExclusiveLock);
245 :
246 : /* Fix the pg_attribute row */
247 3254 : attr_rel = table_open(AttributeRelationId, RowExclusiveLock);
248 :
249 3254 : tuple = SearchSysCacheCopy2(ATTNUM,
250 : ObjectIdGetDatum(myrelid),
251 : Int16GetDatum(myattnum));
252 3254 : if (!HeapTupleIsValid(tuple)) /* shouldn't happen */
253 0 : elog(ERROR, "cache lookup failed for attribute %d of relation %u",
254 : myattnum, myrelid);
255 :
256 3254 : ((Form_pg_attribute) GETSTRUCT(tuple))->atthasdef = false;
257 :
258 3254 : CatalogTupleUpdate(attr_rel, &tuple->t_self, tuple);
259 :
260 : /*
261 : * Our update of the pg_attribute row will force a relcache rebuild, so
262 : * there's nothing else to do here.
263 : */
264 3254 : table_close(attr_rel, RowExclusiveLock);
265 :
266 : /* Keep lock on attribute's rel until end of xact */
267 3254 : relation_close(myrel, NoLock);
268 3254 : }
269 :
270 :
271 : /*
272 : * Get the pg_attrdef OID of the default expression for a column
273 : * identified by relation OID and column number.
274 : *
275 : * Returns InvalidOid if there is no such pg_attrdef entry.
276 : */
277 : Oid
278 218 : GetAttrDefaultOid(Oid relid, AttrNumber attnum)
279 : {
280 218 : Oid result = InvalidOid;
281 : Relation attrdef;
282 : ScanKeyData keys[2];
283 : SysScanDesc scan;
284 : HeapTuple tup;
285 :
286 218 : attrdef = table_open(AttrDefaultRelationId, AccessShareLock);
287 218 : ScanKeyInit(&keys[0],
288 : Anum_pg_attrdef_adrelid,
289 : BTEqualStrategyNumber,
290 : F_OIDEQ,
291 : ObjectIdGetDatum(relid));
292 218 : ScanKeyInit(&keys[1],
293 : Anum_pg_attrdef_adnum,
294 : BTEqualStrategyNumber,
295 : F_INT2EQ,
296 : Int16GetDatum(attnum));
297 218 : scan = systable_beginscan(attrdef, AttrDefaultIndexId, true,
298 : NULL, 2, keys);
299 :
300 218 : if (HeapTupleIsValid(tup = systable_getnext(scan)))
301 : {
302 218 : Form_pg_attrdef atdform = (Form_pg_attrdef) GETSTRUCT(tup);
303 :
304 218 : result = atdform->oid;
305 : }
306 :
307 218 : systable_endscan(scan);
308 218 : table_close(attrdef, AccessShareLock);
309 :
310 218 : return result;
311 : }
312 :
313 : /*
314 : * Given a pg_attrdef OID, return the relation OID and column number of
315 : * the owning column (represented as an ObjectAddress for convenience).
316 : *
317 : * Returns InvalidObjectAddress if there is no such pg_attrdef entry.
318 : */
319 : ObjectAddress
320 3224 : GetAttrDefaultColumnAddress(Oid attrdefoid)
321 : {
322 3224 : ObjectAddress result = InvalidObjectAddress;
323 : Relation attrdef;
324 : ScanKeyData skey[1];
325 : SysScanDesc scan;
326 : HeapTuple tup;
327 :
328 3224 : attrdef = table_open(AttrDefaultRelationId, AccessShareLock);
329 3224 : ScanKeyInit(&skey[0],
330 : Anum_pg_attrdef_oid,
331 : BTEqualStrategyNumber, F_OIDEQ,
332 : ObjectIdGetDatum(attrdefoid));
333 3224 : scan = systable_beginscan(attrdef, AttrDefaultOidIndexId, true,
334 : NULL, 1, skey);
335 :
336 3224 : if (HeapTupleIsValid(tup = systable_getnext(scan)))
337 : {
338 3206 : Form_pg_attrdef atdform = (Form_pg_attrdef) GETSTRUCT(tup);
339 :
340 3206 : result.classId = RelationRelationId;
341 3206 : result.objectId = atdform->adrelid;
342 3206 : result.objectSubId = atdform->adnum;
343 : }
344 :
345 3224 : systable_endscan(scan);
346 3224 : table_close(attrdef, AccessShareLock);
347 :
348 3224 : return result;
349 : }
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