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Diffstat (limited to 'src/backend/catalog/pg_attrdef.c')
| -rw-r--r-- | src/backend/catalog/pg_attrdef.c | 413 |
1 files changed, 413 insertions, 0 deletions
diff --git a/src/backend/catalog/pg_attrdef.c b/src/backend/catalog/pg_attrdef.c new file mode 100644 index 0000000..c5d4a99 --- /dev/null +++ b/src/backend/catalog/pg_attrdef.c @@ -0,0 +1,413 @@ +/*------------------------------------------------------------------------- + * + * pg_attrdef.c + * routines to support manipulation of the pg_attrdef relation + * + * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group + * Portions Copyright (c) 1994, Regents of the University of California + * + * + * IDENTIFICATION + * src/backend/catalog/pg_attrdef.c + * + *------------------------------------------------------------------------- + */ +#include "postgres.h" + +#include "access/genam.h" +#include "access/relation.h" +#include "access/table.h" +#include "catalog/catalog.h" +#include "catalog/dependency.h" +#include "catalog/indexing.h" +#include "catalog/objectaccess.h" +#include "catalog/pg_attrdef.h" +#include "executor/executor.h" +#include "optimizer/optimizer.h" +#include "utils/array.h" +#include "utils/builtins.h" +#include "utils/fmgroids.h" +#include "utils/rel.h" +#include "utils/syscache.h" + + +/* + * Store a default expression for column attnum of relation rel. + * + * Returns the OID of the new pg_attrdef tuple. + * + * add_column_mode must be true if we are storing the default for a new + * attribute, and false if it's for an already existing attribute. The reason + * for this is that the missing value must never be updated after it is set, + * which can only be when a column is added to the table. Otherwise we would + * in effect be changing existing tuples. + */ +Oid +StoreAttrDefault(Relation rel, AttrNumber attnum, + Node *expr, bool is_internal, bool add_column_mode) +{ + char *adbin; + Relation adrel; + HeapTuple tuple; + Datum values[4]; + static bool nulls[4] = {false, false, false, false}; + Relation attrrel; + HeapTuple atttup; + Form_pg_attribute attStruct; + char attgenerated; + Oid attrdefOid; + ObjectAddress colobject, + defobject; + + adrel = table_open(AttrDefaultRelationId, RowExclusiveLock); + + /* + * Flatten expression to string form for storage. + */ + adbin = nodeToString(expr); + + /* + * Make the pg_attrdef entry. + */ + attrdefOid = GetNewOidWithIndex(adrel, AttrDefaultOidIndexId, + Anum_pg_attrdef_oid); + values[Anum_pg_attrdef_oid - 1] = ObjectIdGetDatum(attrdefOid); + values[Anum_pg_attrdef_adrelid - 1] = RelationGetRelid(rel); + values[Anum_pg_attrdef_adnum - 1] = attnum; + values[Anum_pg_attrdef_adbin - 1] = CStringGetTextDatum(adbin); + + tuple = heap_form_tuple(adrel->rd_att, values, nulls); + CatalogTupleInsert(adrel, tuple); + + defobject.classId = AttrDefaultRelationId; + defobject.objectId = attrdefOid; + defobject.objectSubId = 0; + + table_close(adrel, RowExclusiveLock); + + /* now can free some of the stuff allocated above */ + pfree(DatumGetPointer(values[Anum_pg_attrdef_adbin - 1])); + heap_freetuple(tuple); + pfree(adbin); + + /* + * Update the pg_attribute entry for the column to show that a default + * exists. + */ + attrrel = table_open(AttributeRelationId, RowExclusiveLock); + atttup = SearchSysCacheCopy2(ATTNUM, + ObjectIdGetDatum(RelationGetRelid(rel)), + Int16GetDatum(attnum)); + if (!HeapTupleIsValid(atttup)) + elog(ERROR, "cache lookup failed for attribute %d of relation %u", + attnum, RelationGetRelid(rel)); + attStruct = (Form_pg_attribute) GETSTRUCT(atttup); + attgenerated = attStruct->attgenerated; + if (!attStruct->atthasdef) + { + Form_pg_attribute defAttStruct; + + ExprState *exprState; + Expr *expr2 = (Expr *) expr; + EState *estate = NULL; + ExprContext *econtext; + Datum valuesAtt[Natts_pg_attribute]; + bool nullsAtt[Natts_pg_attribute]; + bool replacesAtt[Natts_pg_attribute]; + Datum missingval = (Datum) 0; + bool missingIsNull = true; + + MemSet(valuesAtt, 0, sizeof(valuesAtt)); + MemSet(nullsAtt, false, sizeof(nullsAtt)); + MemSet(replacesAtt, false, sizeof(replacesAtt)); + valuesAtt[Anum_pg_attribute_atthasdef - 1] = true; + replacesAtt[Anum_pg_attribute_atthasdef - 1] = true; + + if (rel->rd_rel->relkind == RELKIND_RELATION && add_column_mode && + !attgenerated) + { + expr2 = expression_planner(expr2); + estate = CreateExecutorState(); + exprState = ExecPrepareExpr(expr2, estate); + econtext = GetPerTupleExprContext(estate); + + missingval = ExecEvalExpr(exprState, econtext, + &missingIsNull); + + FreeExecutorState(estate); + + defAttStruct = TupleDescAttr(rel->rd_att, attnum - 1); + + if (missingIsNull) + { + /* if the default evaluates to NULL, just store a NULL array */ + missingval = (Datum) 0; + } + else + { + /* otherwise make a one-element array of the value */ + missingval = PointerGetDatum(construct_array(&missingval, + 1, + defAttStruct->atttypid, + defAttStruct->attlen, + defAttStruct->attbyval, + defAttStruct->attalign)); + } + + valuesAtt[Anum_pg_attribute_atthasmissing - 1] = !missingIsNull; + replacesAtt[Anum_pg_attribute_atthasmissing - 1] = true; + valuesAtt[Anum_pg_attribute_attmissingval - 1] = missingval; + replacesAtt[Anum_pg_attribute_attmissingval - 1] = true; + nullsAtt[Anum_pg_attribute_attmissingval - 1] = missingIsNull; + } + atttup = heap_modify_tuple(atttup, RelationGetDescr(attrrel), + valuesAtt, nullsAtt, replacesAtt); + + CatalogTupleUpdate(attrrel, &atttup->t_self, atttup); + + if (!missingIsNull) + pfree(DatumGetPointer(missingval)); + } + table_close(attrrel, RowExclusiveLock); + heap_freetuple(atttup); + + /* + * Make a dependency so that the pg_attrdef entry goes away if the column + * (or whole table) is deleted. In the case of a generated column, make + * it an internal dependency to prevent the default expression from being + * deleted separately. + */ + colobject.classId = RelationRelationId; + colobject.objectId = RelationGetRelid(rel); + colobject.objectSubId = attnum; + + recordDependencyOn(&defobject, &colobject, + attgenerated ? DEPENDENCY_INTERNAL : DEPENDENCY_AUTO); + + /* + * Record dependencies on objects used in the expression, too. + */ + recordDependencyOnSingleRelExpr(&defobject, expr, RelationGetRelid(rel), + DEPENDENCY_NORMAL, + DEPENDENCY_NORMAL, false); + + /* + * Post creation hook for attribute defaults. + * + * XXX. ALTER TABLE ALTER COLUMN SET/DROP DEFAULT is implemented with a + * couple of deletion/creation of the attribute's default entry, so the + * callee should check existence of an older version of this entry if it + * needs to distinguish. + */ + InvokeObjectPostCreateHookArg(AttrDefaultRelationId, + RelationGetRelid(rel), attnum, is_internal); + + return attrdefOid; +} + + +/* + * RemoveAttrDefault + * + * If the specified relation/attribute has a default, remove it. + * (If no default, raise error if complain is true, else return quietly.) + */ +void +RemoveAttrDefault(Oid relid, AttrNumber attnum, + DropBehavior behavior, bool complain, bool internal) +{ + Relation attrdef_rel; + ScanKeyData scankeys[2]; + SysScanDesc scan; + HeapTuple tuple; + bool found = false; + + attrdef_rel = table_open(AttrDefaultRelationId, RowExclusiveLock); + + ScanKeyInit(&scankeys[0], + Anum_pg_attrdef_adrelid, + BTEqualStrategyNumber, F_OIDEQ, + ObjectIdGetDatum(relid)); + ScanKeyInit(&scankeys[1], + Anum_pg_attrdef_adnum, + BTEqualStrategyNumber, F_INT2EQ, + Int16GetDatum(attnum)); + + scan = systable_beginscan(attrdef_rel, AttrDefaultIndexId, true, + NULL, 2, scankeys); + + /* There should be at most one matching tuple, but we loop anyway */ + while (HeapTupleIsValid(tuple = systable_getnext(scan))) + { + ObjectAddress object; + Form_pg_attrdef attrtuple = (Form_pg_attrdef) GETSTRUCT(tuple); + + object.classId = AttrDefaultRelationId; + object.objectId = attrtuple->oid; + object.objectSubId = 0; + + performDeletion(&object, behavior, + internal ? PERFORM_DELETION_INTERNAL : 0); + + found = true; + } + + systable_endscan(scan); + table_close(attrdef_rel, RowExclusiveLock); + + if (complain && !found) + elog(ERROR, "could not find attrdef tuple for relation %u attnum %d", + relid, attnum); +} + +/* + * RemoveAttrDefaultById + * + * Remove a pg_attrdef entry specified by OID. This is the guts of + * attribute-default removal. Note it should be called via performDeletion, + * not directly. + */ +void +RemoveAttrDefaultById(Oid attrdefId) +{ + Relation attrdef_rel; + Relation attr_rel; + Relation myrel; + ScanKeyData scankeys[1]; + SysScanDesc scan; + HeapTuple tuple; + Oid myrelid; + AttrNumber myattnum; + + /* Grab an appropriate lock on the pg_attrdef relation */ + attrdef_rel = table_open(AttrDefaultRelationId, RowExclusiveLock); + + /* Find the pg_attrdef tuple */ + ScanKeyInit(&scankeys[0], + Anum_pg_attrdef_oid, + BTEqualStrategyNumber, F_OIDEQ, + ObjectIdGetDatum(attrdefId)); + + scan = systable_beginscan(attrdef_rel, AttrDefaultOidIndexId, true, + NULL, 1, scankeys); + + tuple = systable_getnext(scan); + if (!HeapTupleIsValid(tuple)) + elog(ERROR, "could not find tuple for attrdef %u", attrdefId); + + myrelid = ((Form_pg_attrdef) GETSTRUCT(tuple))->adrelid; + myattnum = ((Form_pg_attrdef) GETSTRUCT(tuple))->adnum; + + /* Get an exclusive lock on the relation owning the attribute */ + myrel = relation_open(myrelid, AccessExclusiveLock); + + /* Now we can delete the pg_attrdef row */ + CatalogTupleDelete(attrdef_rel, &tuple->t_self); + + systable_endscan(scan); + table_close(attrdef_rel, RowExclusiveLock); + + /* Fix the pg_attribute row */ + attr_rel = table_open(AttributeRelationId, RowExclusiveLock); + + tuple = SearchSysCacheCopy2(ATTNUM, + ObjectIdGetDatum(myrelid), + Int16GetDatum(myattnum)); + if (!HeapTupleIsValid(tuple)) /* shouldn't happen */ + elog(ERROR, "cache lookup failed for attribute %d of relation %u", + myattnum, myrelid); + + ((Form_pg_attribute) GETSTRUCT(tuple))->atthasdef = false; + + CatalogTupleUpdate(attr_rel, &tuple->t_self, tuple); + + /* + * Our update of the pg_attribute row will force a relcache rebuild, so + * there's nothing else to do here. + */ + table_close(attr_rel, RowExclusiveLock); + + /* Keep lock on attribute's rel until end of xact */ + relation_close(myrel, NoLock); +} + + +/* + * Get the pg_attrdef OID of the default expression for a column + * identified by relation OID and and column number. + * + * Returns InvalidOid if there is no such pg_attrdef entry. + */ +Oid +GetAttrDefaultOid(Oid relid, AttrNumber attnum) +{ + Oid result = InvalidOid; + Relation attrdef; + ScanKeyData keys[2]; + SysScanDesc scan; + HeapTuple tup; + + attrdef = table_open(AttrDefaultRelationId, AccessShareLock); + ScanKeyInit(&keys[0], + Anum_pg_attrdef_adrelid, + BTEqualStrategyNumber, + F_OIDEQ, + ObjectIdGetDatum(relid)); + ScanKeyInit(&keys[1], + Anum_pg_attrdef_adnum, + BTEqualStrategyNumber, + F_INT2EQ, + Int16GetDatum(attnum)); + scan = systable_beginscan(attrdef, AttrDefaultIndexId, true, + NULL, 2, keys); + + if (HeapTupleIsValid(tup = systable_getnext(scan))) + { + Form_pg_attrdef atdform = (Form_pg_attrdef) GETSTRUCT(tup); + + result = atdform->oid; + } + + systable_endscan(scan); + table_close(attrdef, AccessShareLock); + + return result; +} + +/* + * Given a pg_attrdef OID, return the relation OID and column number of + * the owning column (represented as an ObjectAddress for convenience). + * + * Returns InvalidObjectAddress if there is no such pg_attrdef entry. + */ +ObjectAddress +GetAttrDefaultColumnAddress(Oid attrdefoid) +{ + ObjectAddress result = InvalidObjectAddress; + Relation attrdef; + ScanKeyData skey[1]; + SysScanDesc scan; + HeapTuple tup; + + attrdef = table_open(AttrDefaultRelationId, AccessShareLock); + ScanKeyInit(&skey[0], + Anum_pg_attrdef_oid, + BTEqualStrategyNumber, F_OIDEQ, + ObjectIdGetDatum(attrdefoid)); + scan = systable_beginscan(attrdef, AttrDefaultOidIndexId, true, + NULL, 1, skey); + + if (HeapTupleIsValid(tup = systable_getnext(scan))) + { + Form_pg_attrdef atdform = (Form_pg_attrdef) GETSTRUCT(tup); + + result.classId = RelationRelationId; + result.objectId = atdform->adrelid; + result.objectSubId = atdform->adnum; + } + + systable_endscan(scan); + table_close(attrdef, AccessShareLock); + + return result; +} |