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) 1996-2024, 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/genam.h"
18 : #include "access/relation.h"
19 : #include "access/table.h"
20 : #include "catalog/catalog.h"
21 : #include "catalog/dependency.h"
22 : #include "catalog/indexing.h"
23 : #include "catalog/objectaccess.h"
24 : #include "catalog/pg_attrdef.h"
25 : #include "executor/executor.h"
26 : #include "optimizer/optimizer.h"
27 : #include "utils/array.h"
28 : #include "utils/builtins.h"
29 : #include "utils/fmgroids.h"
30 : #include "utils/rel.h"
31 : #include "utils/syscache.h"
32 :
33 :
34 : /*
35 : * Store a default expression for column attnum of relation rel.
36 : *
37 : * Returns the OID of the new pg_attrdef tuple.
38 : *
39 : * add_column_mode must be true if we are storing the default for a new
40 : * attribute, and false if it's for an already existing attribute. The reason
41 : * for this is that the missing value must never be updated after it is set,
42 : * which can only be when a column is added to the table. Otherwise we would
43 : * in effect be changing existing tuples.
44 : */
45 : Oid
46 3742 : StoreAttrDefault(Relation rel, AttrNumber attnum,
47 : Node *expr, bool is_internal, bool add_column_mode)
48 : {
49 : char *adbin;
50 : Relation adrel;
51 : HeapTuple tuple;
52 : Datum values[4];
53 : static bool nulls[4] = {false, false, false, false};
54 : Relation attrrel;
55 : HeapTuple atttup;
56 : Form_pg_attribute attStruct;
57 : char attgenerated;
58 : Oid attrdefOid;
59 : ObjectAddress colobject,
60 : defobject;
61 :
62 3742 : adrel = table_open(AttrDefaultRelationId, RowExclusiveLock);
63 :
64 : /*
65 : * Flatten expression to string form for storage.
66 : */
67 3742 : adbin = nodeToString(expr);
68 :
69 : /*
70 : * Make the pg_attrdef entry.
71 : */
72 3742 : attrdefOid = GetNewOidWithIndex(adrel, AttrDefaultOidIndexId,
73 : Anum_pg_attrdef_oid);
74 3742 : values[Anum_pg_attrdef_oid - 1] = ObjectIdGetDatum(attrdefOid);
75 3742 : values[Anum_pg_attrdef_adrelid - 1] = RelationGetRelid(rel);
76 3742 : values[Anum_pg_attrdef_adnum - 1] = attnum;
77 3742 : values[Anum_pg_attrdef_adbin - 1] = CStringGetTextDatum(adbin);
78 :
79 3742 : tuple = heap_form_tuple(adrel->rd_att, values, nulls);
80 3742 : CatalogTupleInsert(adrel, tuple);
81 :
82 3742 : defobject.classId = AttrDefaultRelationId;
83 3742 : defobject.objectId = attrdefOid;
84 3742 : defobject.objectSubId = 0;
85 :
86 3742 : table_close(adrel, RowExclusiveLock);
87 :
88 : /* now can free some of the stuff allocated above */
89 3742 : pfree(DatumGetPointer(values[Anum_pg_attrdef_adbin - 1]));
90 3742 : heap_freetuple(tuple);
91 3742 : pfree(adbin);
92 :
93 : /*
94 : * Update the pg_attribute entry for the column to show that a default
95 : * exists.
96 : */
97 3742 : attrrel = table_open(AttributeRelationId, RowExclusiveLock);
98 3742 : atttup = SearchSysCacheCopy2(ATTNUM,
99 : ObjectIdGetDatum(RelationGetRelid(rel)),
100 : Int16GetDatum(attnum));
101 3742 : if (!HeapTupleIsValid(atttup))
102 0 : elog(ERROR, "cache lookup failed for attribute %d of relation %u",
103 : attnum, RelationGetRelid(rel));
104 3742 : attStruct = (Form_pg_attribute) GETSTRUCT(atttup);
105 3742 : attgenerated = attStruct->attgenerated;
106 3742 : if (!attStruct->atthasdef)
107 : {
108 : Form_pg_attribute defAttStruct;
109 :
110 : ExprState *exprState;
111 3742 : Expr *expr2 = (Expr *) expr;
112 3742 : EState *estate = NULL;
113 : ExprContext *econtext;
114 3742 : Datum valuesAtt[Natts_pg_attribute] = {0};
115 3742 : bool nullsAtt[Natts_pg_attribute] = {0};
116 3742 : bool replacesAtt[Natts_pg_attribute] = {0};
117 3742 : Datum missingval = (Datum) 0;
118 3742 : bool missingIsNull = true;
119 :
120 3742 : valuesAtt[Anum_pg_attribute_atthasdef - 1] = true;
121 3742 : replacesAtt[Anum_pg_attribute_atthasdef - 1] = true;
122 :
123 3742 : if (rel->rd_rel->relkind == RELKIND_RELATION && add_column_mode &&
124 : !attgenerated)
125 : {
126 454 : expr2 = expression_planner(expr2);
127 454 : estate = CreateExecutorState();
128 454 : exprState = ExecPrepareExpr(expr2, estate);
129 454 : econtext = GetPerTupleExprContext(estate);
130 :
131 454 : missingval = ExecEvalExpr(exprState, econtext,
132 : &missingIsNull);
133 :
134 454 : FreeExecutorState(estate);
135 :
136 454 : defAttStruct = TupleDescAttr(rel->rd_att, attnum - 1);
137 :
138 454 : if (missingIsNull)
139 : {
140 : /* if the default evaluates to NULL, just store a NULL array */
141 0 : missingval = (Datum) 0;
142 : }
143 : else
144 : {
145 : /* otherwise make a one-element array of the value */
146 454 : missingval = PointerGetDatum(construct_array(&missingval,
147 : 1,
148 : defAttStruct->atttypid,
149 454 : defAttStruct->attlen,
150 454 : defAttStruct->attbyval,
151 454 : defAttStruct->attalign));
152 : }
153 :
154 454 : valuesAtt[Anum_pg_attribute_atthasmissing - 1] = !missingIsNull;
155 454 : replacesAtt[Anum_pg_attribute_atthasmissing - 1] = true;
156 454 : valuesAtt[Anum_pg_attribute_attmissingval - 1] = missingval;
157 454 : replacesAtt[Anum_pg_attribute_attmissingval - 1] = true;
158 454 : nullsAtt[Anum_pg_attribute_attmissingval - 1] = missingIsNull;
159 : }
160 3742 : atttup = heap_modify_tuple(atttup, RelationGetDescr(attrrel),
161 : valuesAtt, nullsAtt, replacesAtt);
162 :
163 3742 : CatalogTupleUpdate(attrrel, &atttup->t_self, atttup);
164 :
165 3742 : if (!missingIsNull)
166 454 : pfree(DatumGetPointer(missingval));
167 : }
168 3742 : table_close(attrrel, RowExclusiveLock);
169 3742 : heap_freetuple(atttup);
170 :
171 : /*
172 : * Make a dependency so that the pg_attrdef entry goes away if the column
173 : * (or whole table) is deleted. In the case of a generated column, make
174 : * it an internal dependency to prevent the default expression from being
175 : * deleted separately.
176 : */
177 3742 : colobject.classId = RelationRelationId;
178 3742 : colobject.objectId = RelationGetRelid(rel);
179 3742 : colobject.objectSubId = attnum;
180 :
181 3742 : recordDependencyOn(&defobject, &colobject,
182 : attgenerated ? DEPENDENCY_INTERNAL : DEPENDENCY_AUTO);
183 :
184 : /*
185 : * Record dependencies on objects used in the expression, too.
186 : */
187 3742 : recordDependencyOnSingleRelExpr(&defobject, expr, RelationGetRelid(rel),
188 : DEPENDENCY_NORMAL,
189 : DEPENDENCY_NORMAL, false);
190 :
191 : /*
192 : * Post creation hook for attribute defaults.
193 : *
194 : * XXX. ALTER TABLE ALTER COLUMN SET/DROP DEFAULT is implemented with a
195 : * couple of deletion/creation of the attribute's default entry, so the
196 : * callee should check existence of an older version of this entry if it
197 : * needs to distinguish.
198 : */
199 3742 : InvokeObjectPostCreateHookArg(AttrDefaultRelationId,
200 : RelationGetRelid(rel), attnum, is_internal);
201 :
202 3742 : return attrdefOid;
203 : }
204 :
205 :
206 : /*
207 : * RemoveAttrDefault
208 : *
209 : * If the specified relation/attribute has a default, remove it.
210 : * (If no default, raise error if complain is true, else return quietly.)
211 : */
212 : void
213 712 : RemoveAttrDefault(Oid relid, AttrNumber attnum,
214 : DropBehavior behavior, bool complain, bool internal)
215 : {
216 : Relation attrdef_rel;
217 : ScanKeyData scankeys[2];
218 : SysScanDesc scan;
219 : HeapTuple tuple;
220 712 : bool found = false;
221 :
222 712 : attrdef_rel = table_open(AttrDefaultRelationId, RowExclusiveLock);
223 :
224 712 : ScanKeyInit(&scankeys[0],
225 : Anum_pg_attrdef_adrelid,
226 : BTEqualStrategyNumber, F_OIDEQ,
227 : ObjectIdGetDatum(relid));
228 712 : ScanKeyInit(&scankeys[1],
229 : Anum_pg_attrdef_adnum,
230 : BTEqualStrategyNumber, F_INT2EQ,
231 : Int16GetDatum(attnum));
232 :
233 712 : scan = systable_beginscan(attrdef_rel, AttrDefaultIndexId, true,
234 : NULL, 2, scankeys);
235 :
236 : /* There should be at most one matching tuple, but we loop anyway */
237 1184 : while (HeapTupleIsValid(tuple = systable_getnext(scan)))
238 : {
239 : ObjectAddress object;
240 472 : Form_pg_attrdef attrtuple = (Form_pg_attrdef) GETSTRUCT(tuple);
241 :
242 472 : object.classId = AttrDefaultRelationId;
243 472 : object.objectId = attrtuple->oid;
244 472 : object.objectSubId = 0;
245 :
246 472 : performDeletion(&object, behavior,
247 : internal ? PERFORM_DELETION_INTERNAL : 0);
248 :
249 472 : found = true;
250 : }
251 :
252 712 : systable_endscan(scan);
253 712 : table_close(attrdef_rel, RowExclusiveLock);
254 :
255 712 : if (complain && !found)
256 0 : elog(ERROR, "could not find attrdef tuple for relation %u attnum %d",
257 : relid, attnum);
258 712 : }
259 :
260 : /*
261 : * RemoveAttrDefaultById
262 : *
263 : * Remove a pg_attrdef entry specified by OID. This is the guts of
264 : * attribute-default removal. Note it should be called via performDeletion,
265 : * not directly.
266 : */
267 : void
268 2824 : RemoveAttrDefaultById(Oid attrdefId)
269 : {
270 : Relation attrdef_rel;
271 : Relation attr_rel;
272 : Relation myrel;
273 : ScanKeyData scankeys[1];
274 : SysScanDesc scan;
275 : HeapTuple tuple;
276 : Oid myrelid;
277 : AttrNumber myattnum;
278 :
279 : /* Grab an appropriate lock on the pg_attrdef relation */
280 2824 : attrdef_rel = table_open(AttrDefaultRelationId, RowExclusiveLock);
281 :
282 : /* Find the pg_attrdef tuple */
283 2824 : ScanKeyInit(&scankeys[0],
284 : Anum_pg_attrdef_oid,
285 : BTEqualStrategyNumber, F_OIDEQ,
286 : ObjectIdGetDatum(attrdefId));
287 :
288 2824 : scan = systable_beginscan(attrdef_rel, AttrDefaultOidIndexId, true,
289 : NULL, 1, scankeys);
290 :
291 2824 : tuple = systable_getnext(scan);
292 2824 : if (!HeapTupleIsValid(tuple))
293 0 : elog(ERROR, "could not find tuple for attrdef %u", attrdefId);
294 :
295 2824 : myrelid = ((Form_pg_attrdef) GETSTRUCT(tuple))->adrelid;
296 2824 : myattnum = ((Form_pg_attrdef) GETSTRUCT(tuple))->adnum;
297 :
298 : /* Get an exclusive lock on the relation owning the attribute */
299 2824 : myrel = relation_open(myrelid, AccessExclusiveLock);
300 :
301 : /* Now we can delete the pg_attrdef row */
302 2824 : CatalogTupleDelete(attrdef_rel, &tuple->t_self);
303 :
304 2824 : systable_endscan(scan);
305 2824 : table_close(attrdef_rel, RowExclusiveLock);
306 :
307 : /* Fix the pg_attribute row */
308 2824 : attr_rel = table_open(AttributeRelationId, RowExclusiveLock);
309 :
310 2824 : tuple = SearchSysCacheCopy2(ATTNUM,
311 : ObjectIdGetDatum(myrelid),
312 : Int16GetDatum(myattnum));
313 2824 : if (!HeapTupleIsValid(tuple)) /* shouldn't happen */
314 0 : elog(ERROR, "cache lookup failed for attribute %d of relation %u",
315 : myattnum, myrelid);
316 :
317 2824 : ((Form_pg_attribute) GETSTRUCT(tuple))->atthasdef = false;
318 :
319 2824 : CatalogTupleUpdate(attr_rel, &tuple->t_self, tuple);
320 :
321 : /*
322 : * Our update of the pg_attribute row will force a relcache rebuild, so
323 : * there's nothing else to do here.
324 : */
325 2824 : table_close(attr_rel, RowExclusiveLock);
326 :
327 : /* Keep lock on attribute's rel until end of xact */
328 2824 : relation_close(myrel, NoLock);
329 2824 : }
330 :
331 :
332 : /*
333 : * Get the pg_attrdef OID of the default expression for a column
334 : * identified by relation OID and column number.
335 : *
336 : * Returns InvalidOid if there is no such pg_attrdef entry.
337 : */
338 : Oid
339 116 : GetAttrDefaultOid(Oid relid, AttrNumber attnum)
340 : {
341 116 : Oid result = InvalidOid;
342 : Relation attrdef;
343 : ScanKeyData keys[2];
344 : SysScanDesc scan;
345 : HeapTuple tup;
346 :
347 116 : attrdef = table_open(AttrDefaultRelationId, AccessShareLock);
348 116 : ScanKeyInit(&keys[0],
349 : Anum_pg_attrdef_adrelid,
350 : BTEqualStrategyNumber,
351 : F_OIDEQ,
352 : ObjectIdGetDatum(relid));
353 116 : ScanKeyInit(&keys[1],
354 : Anum_pg_attrdef_adnum,
355 : BTEqualStrategyNumber,
356 : F_INT2EQ,
357 : Int16GetDatum(attnum));
358 116 : scan = systable_beginscan(attrdef, AttrDefaultIndexId, true,
359 : NULL, 2, keys);
360 :
361 116 : if (HeapTupleIsValid(tup = systable_getnext(scan)))
362 : {
363 116 : Form_pg_attrdef atdform = (Form_pg_attrdef) GETSTRUCT(tup);
364 :
365 116 : result = atdform->oid;
366 : }
367 :
368 116 : systable_endscan(scan);
369 116 : table_close(attrdef, AccessShareLock);
370 :
371 116 : return result;
372 : }
373 :
374 : /*
375 : * Given a pg_attrdef OID, return the relation OID and column number of
376 : * the owning column (represented as an ObjectAddress for convenience).
377 : *
378 : * Returns InvalidObjectAddress if there is no such pg_attrdef entry.
379 : */
380 : ObjectAddress
381 2812 : GetAttrDefaultColumnAddress(Oid attrdefoid)
382 : {
383 2812 : ObjectAddress result = InvalidObjectAddress;
384 : Relation attrdef;
385 : ScanKeyData skey[1];
386 : SysScanDesc scan;
387 : HeapTuple tup;
388 :
389 2812 : attrdef = table_open(AttrDefaultRelationId, AccessShareLock);
390 2812 : ScanKeyInit(&skey[0],
391 : Anum_pg_attrdef_oid,
392 : BTEqualStrategyNumber, F_OIDEQ,
393 : ObjectIdGetDatum(attrdefoid));
394 2812 : scan = systable_beginscan(attrdef, AttrDefaultOidIndexId, true,
395 : NULL, 1, skey);
396 :
397 2812 : if (HeapTupleIsValid(tup = systable_getnext(scan)))
398 : {
399 2794 : Form_pg_attrdef atdform = (Form_pg_attrdef) GETSTRUCT(tup);
400 :
401 2794 : result.classId = RelationRelationId;
402 2794 : result.objectId = atdform->adrelid;
403 2794 : result.objectSubId = atdform->adnum;
404 : }
405 :
406 2812 : systable_endscan(scan);
407 2812 : table_close(attrdef, AccessShareLock);
408 :
409 2812 : return result;
410 : }
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