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Avoid duplicates in ALTER ... DEPENDS ON EXTENSION

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If the command is attempted for an extension that the object already
depends on, silently do nothing.

In particular, this means that if a database containing multiple such
entries is dumped, the restore will silently do the right thing and
record just the first one.  (At least, in a world where pg_dump does
dump such entries -- which it doesn't currently, but it will.)

Backpatch to 9.6, where this kind of dependency was introduced.

Reviewed-by: Ibrar Ahmed, Tom Lane (offlist)
Discussion: https://postgr.es/m/20200217225333.GA30974@alvherre.pgsql
This commit is contained in:
Alvaro Herrera
2020-03-11 11:04:59 -03:00
parent 8bca5f9354
commit b7739ebecd
5 changed files with 54 additions and 1 deletions
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43
src/backend/catalog/pg_depend.c
View File

@ -648,6 +648,49 @@ getExtensionOfObject(Oid classId, Oid objectId)
return result;
}
/*
* Return (possibly NIL) list of extensions that the given object depends on
* in DEPENDENCY_AUTO_EXTENSION mode.
*/
List *
getAutoExtensionsOfObject(Oid classId, Oid objectId)
{
List *result = NIL;
Relation depRel;
ScanKeyData key[2];
SysScanDesc scan;
HeapTuple tup;
depRel = table_open(DependRelationId, AccessShareLock);
ScanKeyInit(&key[0],
Anum_pg_depend_classid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(classId));
ScanKeyInit(&key[1],
Anum_pg_depend_objid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(objectId));
scan = systable_beginscan(depRel, DependDependerIndexId, true,
NULL, 2, key);
while (HeapTupleIsValid((tup = systable_getnext(scan))))
{
Form_pg_depend depform = (Form_pg_depend) GETSTRUCT(tup);
if (depform->refclassid == ExtensionRelationId &&
depform->deptype == DEPENDENCY_AUTO_EXTENSION)
result = lappend_oid(result, depform->refobjid);
}
systable_endscan(scan);
table_close(depRel, AccessShareLock);
return result;
}
/*
* Detect whether a sequence is marked as "owned" by a column
*

7
src/backend/commands/alter.c
View File

@ -434,6 +434,7 @@ ExecAlterObjectDependsStmt(AlterObjectDependsStmt *stmt, ObjectAddress *refAddre
ObjectAddress address;
ObjectAddress refAddr;
Relation rel;
List *currexts;
address =
get_object_address_rv(stmt->objectType, stmt->relation, (List *) stmt->object,
@ -463,7 +464,11 @@ ExecAlterObjectDependsStmt(AlterObjectDependsStmt *stmt, ObjectAddress *refAddre
if (refAddress)
*refAddress = refAddr;
recordDependencyOn(&address, &refAddr, DEPENDENCY_AUTO_EXTENSION);
/* Avoid duplicates */
currexts = getAutoExtensionsOfObject(address.classId,
address.objectId);
if (!list_member_oid(currexts, refAddr.objectId))
recordDependencyOn(&address, &refAddr, DEPENDENCY_AUTO_EXTENSION);
return address;
}