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/htup_details.h"
18 : #include "access/relation.h"
19 : #include "access/table.h"
20 : #include "catalog/dependency.h"
21 : #include "catalog/indexing.h"
22 : #include "catalog/objectaccess.h"
23 : #include "catalog/pg_attrdef.h"
24 : #include "utils/builtins.h"
25 : #include "utils/fmgroids.h"
26 : #include "utils/rel.h"
27 : #include "utils/syscache.h"
28 :
29 :
30 : /*
31 : * Store a default expression for column attnum of relation rel.
32 : *
33 : * Returns the OID of the new pg_attrdef tuple.
34 : */
35 : Oid
36 4896 : StoreAttrDefault(Relation rel, AttrNumber attnum,
37 : Node *expr, bool is_internal)
38 : {
39 : char *adbin;
40 : Relation adrel;
41 : HeapTuple tuple;
42 : Datum values[Natts_pg_attrdef];
43 : static bool nulls[Natts_pg_attrdef] = {false, false, false, false};
44 : Relation attrrel;
45 : HeapTuple atttup;
46 : Form_pg_attribute attStruct;
47 4896 : Datum valuesAtt[Natts_pg_attribute] = {0};
48 4896 : bool nullsAtt[Natts_pg_attribute] = {0};
49 4896 : bool replacesAtt[Natts_pg_attribute] = {0};
50 : char attgenerated;
51 : Oid attrdefOid;
52 : ObjectAddress colobject,
53 : defobject;
54 :
55 4896 : adrel = table_open(AttrDefaultRelationId, RowExclusiveLock);
56 :
57 : /*
58 : * Flatten expression to string form for storage.
59 : */
60 4896 : adbin = nodeToString(expr);
61 :
62 : /*
63 : * Make the pg_attrdef entry.
64 : */
65 4896 : attrdefOid = GetNewOidWithIndex(adrel, AttrDefaultOidIndexId,
66 : Anum_pg_attrdef_oid);
67 4896 : values[Anum_pg_attrdef_oid - 1] = ObjectIdGetDatum(attrdefOid);
68 4896 : values[Anum_pg_attrdef_adrelid - 1] = ObjectIdGetDatum(RelationGetRelid(rel));
69 4896 : values[Anum_pg_attrdef_adnum - 1] = Int16GetDatum(attnum);
70 4896 : values[Anum_pg_attrdef_adbin - 1] = CStringGetTextDatum(adbin);
71 :
72 4896 : tuple = heap_form_tuple(adrel->rd_att, values, nulls);
73 4896 : CatalogTupleInsert(adrel, tuple);
74 :
75 4896 : defobject.classId = AttrDefaultRelationId;
76 4896 : defobject.objectId = attrdefOid;
77 4896 : defobject.objectSubId = 0;
78 :
79 4896 : table_close(adrel, RowExclusiveLock);
80 :
81 : /* now can free some of the stuff allocated above */
82 4896 : pfree(DatumGetPointer(values[Anum_pg_attrdef_adbin - 1]));
83 4896 : heap_freetuple(tuple);
84 4896 : pfree(adbin);
85 :
86 : /*
87 : * Update the pg_attribute entry for the column to show that a default
88 : * exists.
89 : */
90 4896 : attrrel = table_open(AttributeRelationId, RowExclusiveLock);
91 4896 : atttup = SearchSysCacheCopy2(ATTNUM,
92 : ObjectIdGetDatum(RelationGetRelid(rel)),
93 : Int16GetDatum(attnum));
94 4896 : if (!HeapTupleIsValid(atttup))
95 0 : elog(ERROR, "cache lookup failed for attribute %d of relation %u",
96 : attnum, RelationGetRelid(rel));
97 4896 : attStruct = (Form_pg_attribute) GETSTRUCT(atttup);
98 4896 : attgenerated = attStruct->attgenerated;
99 :
100 4896 : valuesAtt[Anum_pg_attribute_atthasdef - 1] = BoolGetDatum(true);
101 4896 : replacesAtt[Anum_pg_attribute_atthasdef - 1] = true;
102 :
103 4896 : atttup = heap_modify_tuple(atttup, RelationGetDescr(attrrel),
104 : valuesAtt, nullsAtt, replacesAtt);
105 :
106 4896 : CatalogTupleUpdate(attrrel, &atttup->t_self, atttup);
107 :
108 4896 : table_close(attrrel, RowExclusiveLock);
109 4896 : heap_freetuple(atttup);
110 :
111 : /*
112 : * Make a dependency so that the pg_attrdef entry goes away if the column
113 : * (or whole table) is deleted. In the case of a generated column, make
114 : * it an internal dependency to prevent the default expression from being
115 : * deleted separately.
116 : */
117 4896 : colobject.classId = RelationRelationId;
118 4896 : colobject.objectId = RelationGetRelid(rel);
119 4896 : colobject.objectSubId = attnum;
120 :
121 4896 : recordDependencyOn(&defobject, &colobject,
122 : attgenerated ? DEPENDENCY_INTERNAL : DEPENDENCY_AUTO);
123 :
124 : /*
125 : * Record dependencies on objects used in the expression, too.
126 : */
127 4896 : recordDependencyOnSingleRelExpr(&defobject, expr, RelationGetRelid(rel),
128 : DEPENDENCY_NORMAL,
129 : DEPENDENCY_NORMAL, false);
130 :
131 : /*
132 : * Post creation hook for attribute defaults.
133 : *
134 : * XXX. ALTER TABLE ALTER COLUMN SET/DROP DEFAULT is implemented with a
135 : * couple of deletion/creation of the attribute's default entry, so the
136 : * callee should check existence of an older version of this entry if it
137 : * needs to distinguish.
138 : */
139 4884 : InvokeObjectPostCreateHookArg(AttrDefaultRelationId,
140 : RelationGetRelid(rel), attnum, is_internal);
141 :
142 4884 : return attrdefOid;
143 : }
144 :
145 :
146 : /*
147 : * RemoveAttrDefault
148 : *
149 : * If the specified relation/attribute has a default, remove it.
150 : * (If no default, raise error if complain is true, else return quietly.)
151 : */
152 : void
153 896 : RemoveAttrDefault(Oid relid, AttrNumber attnum,
154 : DropBehavior behavior, bool complain, bool internal)
155 : {
156 : Relation attrdef_rel;
157 : ScanKeyData scankeys[2];
158 : SysScanDesc scan;
159 : HeapTuple tuple;
160 896 : bool found = false;
161 :
162 896 : attrdef_rel = table_open(AttrDefaultRelationId, RowExclusiveLock);
163 :
164 896 : ScanKeyInit(&scankeys[0],
165 : Anum_pg_attrdef_adrelid,
166 : BTEqualStrategyNumber, F_OIDEQ,
167 : ObjectIdGetDatum(relid));
168 896 : ScanKeyInit(&scankeys[1],
169 : Anum_pg_attrdef_adnum,
170 : BTEqualStrategyNumber, F_INT2EQ,
171 : Int16GetDatum(attnum));
172 :
173 896 : scan = systable_beginscan(attrdef_rel, AttrDefaultIndexId, true,
174 : NULL, 2, scankeys);
175 :
176 : /* There should be at most one matching tuple, but we loop anyway */
177 1512 : while (HeapTupleIsValid(tuple = systable_getnext(scan)))
178 : {
179 : ObjectAddress object;
180 616 : Form_pg_attrdef attrtuple = (Form_pg_attrdef) GETSTRUCT(tuple);
181 :
182 616 : object.classId = AttrDefaultRelationId;
183 616 : object.objectId = attrtuple->oid;
184 616 : object.objectSubId = 0;
185 :
186 616 : performDeletion(&object, behavior,
187 : internal ? PERFORM_DELETION_INTERNAL : 0);
188 :
189 616 : found = true;
190 : }
191 :
192 896 : systable_endscan(scan);
193 896 : table_close(attrdef_rel, RowExclusiveLock);
194 :
195 896 : if (complain && !found)
196 0 : elog(ERROR, "could not find attrdef tuple for relation %u attnum %d",
197 : relid, attnum);
198 896 : }
199 :
200 : /*
201 : * RemoveAttrDefaultById
202 : *
203 : * Remove a pg_attrdef entry specified by OID. This is the guts of
204 : * attribute-default removal. Note it should be called via performDeletion,
205 : * not directly.
206 : */
207 : void
208 3404 : RemoveAttrDefaultById(Oid attrdefId)
209 : {
210 : Relation attrdef_rel;
211 : Relation attr_rel;
212 : Relation myrel;
213 : ScanKeyData scankeys[1];
214 : SysScanDesc scan;
215 : HeapTuple tuple;
216 : Oid myrelid;
217 : AttrNumber myattnum;
218 :
219 : /* Grab an appropriate lock on the pg_attrdef relation */
220 3404 : attrdef_rel = table_open(AttrDefaultRelationId, RowExclusiveLock);
221 :
222 : /* Find the pg_attrdef tuple */
223 3404 : ScanKeyInit(&scankeys[0],
224 : Anum_pg_attrdef_oid,
225 : BTEqualStrategyNumber, F_OIDEQ,
226 : ObjectIdGetDatum(attrdefId));
227 :
228 3404 : scan = systable_beginscan(attrdef_rel, AttrDefaultOidIndexId, true,
229 : NULL, 1, scankeys);
230 :
231 3404 : tuple = systable_getnext(scan);
232 3404 : if (!HeapTupleIsValid(tuple))
233 0 : elog(ERROR, "could not find tuple for attrdef %u", attrdefId);
234 :
235 3404 : myrelid = ((Form_pg_attrdef) GETSTRUCT(tuple))->adrelid;
236 3404 : myattnum = ((Form_pg_attrdef) GETSTRUCT(tuple))->adnum;
237 :
238 : /* Get an exclusive lock on the relation owning the attribute */
239 3404 : myrel = relation_open(myrelid, AccessExclusiveLock);
240 :
241 : /* Now we can delete the pg_attrdef row */
242 3404 : CatalogTupleDelete(attrdef_rel, &tuple->t_self);
243 :
244 3404 : systable_endscan(scan);
245 3404 : table_close(attrdef_rel, RowExclusiveLock);
246 :
247 : /* Fix the pg_attribute row */
248 3404 : attr_rel = table_open(AttributeRelationId, RowExclusiveLock);
249 :
250 3404 : tuple = SearchSysCacheCopy2(ATTNUM,
251 : ObjectIdGetDatum(myrelid),
252 : Int16GetDatum(myattnum));
253 3404 : if (!HeapTupleIsValid(tuple)) /* shouldn't happen */
254 0 : elog(ERROR, "cache lookup failed for attribute %d of relation %u",
255 : myattnum, myrelid);
256 :
257 3404 : ((Form_pg_attribute) GETSTRUCT(tuple))->atthasdef = false;
258 :
259 3404 : CatalogTupleUpdate(attr_rel, &tuple->t_self, tuple);
260 :
261 : /*
262 : * Our update of the pg_attribute row will force a relcache rebuild, so
263 : * there's nothing else to do here.
264 : */
265 3404 : table_close(attr_rel, RowExclusiveLock);
266 :
267 : /* Keep lock on attribute's rel until end of xact */
268 3404 : relation_close(myrel, NoLock);
269 3404 : }
270 :
271 :
272 : /*
273 : * Get the pg_attrdef OID of the default expression for a column
274 : * identified by relation OID and column number.
275 : *
276 : * Returns InvalidOid if there is no such pg_attrdef entry.
277 : */
278 : Oid
279 254 : GetAttrDefaultOid(Oid relid, AttrNumber attnum)
280 : {
281 254 : Oid result = InvalidOid;
282 : Relation attrdef;
283 : ScanKeyData keys[2];
284 : SysScanDesc scan;
285 : HeapTuple tup;
286 :
287 254 : attrdef = table_open(AttrDefaultRelationId, AccessShareLock);
288 254 : ScanKeyInit(&keys[0],
289 : Anum_pg_attrdef_adrelid,
290 : BTEqualStrategyNumber,
291 : F_OIDEQ,
292 : ObjectIdGetDatum(relid));
293 254 : ScanKeyInit(&keys[1],
294 : Anum_pg_attrdef_adnum,
295 : BTEqualStrategyNumber,
296 : F_INT2EQ,
297 : Int16GetDatum(attnum));
298 254 : scan = systable_beginscan(attrdef, AttrDefaultIndexId, true,
299 : NULL, 2, keys);
300 :
301 254 : if (HeapTupleIsValid(tup = systable_getnext(scan)))
302 : {
303 254 : Form_pg_attrdef atdform = (Form_pg_attrdef) GETSTRUCT(tup);
304 :
305 254 : result = atdform->oid;
306 : }
307 :
308 254 : systable_endscan(scan);
309 254 : table_close(attrdef, AccessShareLock);
310 :
311 254 : return result;
312 : }
313 :
314 : /*
315 : * Given a pg_attrdef OID, return the relation OID and column number of
316 : * the owning column (represented as an ObjectAddress for convenience).
317 : *
318 : * Returns InvalidObjectAddress if there is no such pg_attrdef entry.
319 : */
320 : ObjectAddress
321 3760 : GetAttrDefaultColumnAddress(Oid attrdefoid)
322 : {
323 3760 : ObjectAddress result = InvalidObjectAddress;
324 : Relation attrdef;
325 : ScanKeyData skey[1];
326 : SysScanDesc scan;
327 : HeapTuple tup;
328 :
329 3760 : attrdef = table_open(AttrDefaultRelationId, AccessShareLock);
330 3760 : ScanKeyInit(&skey[0],
331 : Anum_pg_attrdef_oid,
332 : BTEqualStrategyNumber, F_OIDEQ,
333 : ObjectIdGetDatum(attrdefoid));
334 3760 : scan = systable_beginscan(attrdef, AttrDefaultOidIndexId, true,
335 : NULL, 1, skey);
336 :
337 3760 : if (HeapTupleIsValid(tup = systable_getnext(scan)))
338 : {
339 3742 : Form_pg_attrdef atdform = (Form_pg_attrdef) GETSTRUCT(tup);
340 :
341 3742 : result.classId = RelationRelationId;
342 3742 : result.objectId = atdform->adrelid;
343 3742 : result.objectSubId = atdform->adnum;
344 : }
345 :
346 3760 : systable_endscan(scan);
347 3760 : table_close(attrdef, AccessShareLock);
348 :
349 3760 : return result;
350 : }
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