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Commit5be594c

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Heed lock protocol in DROP OWNED BY
We were acquiring object locks then deleting objects one by one, insteadof acquiring all object locks first, ignoring those that did not exist,and then deleting all objects together. The latter is the correctprotocol to use, and what this commits changes to code to do. Failingto follow that leads to "cache lookup failed for relation XYZ" errorreports when DROP OWNED runs concurrently with other DDL -- for example,a session termination that removes some temp tables.Author: Álvaro HerreraReported-by: Mithun Chicklore Yogendra (Mithun CY)Reviewed-by: Ahsan Hadi, Tom LaneDiscussion:https://postgr.es/m/CADq3xVZTbzK4ZLKq+dn_vB4QafXXbmMgDP3trY-GuLnib2Ai1w@mail.gmail.com
1 parentf215993 commit5be594c

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4 files changed

+36
-8
lines changed

4 files changed

+36
-8
lines changed

‎src/backend/catalog/dependency.c

Lines changed: 9 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -200,8 +200,6 @@ static void reportDependentObjects(const ObjectAddresses *targetObjects,
200200
staticvoiddeleteOneObject(constObjectAddress*object,
201201
Relation*depRel,int32flags);
202202
staticvoiddoDeletion(constObjectAddress*object,intflags);
203-
staticvoidAcquireDeletionLock(constObjectAddress*object,intflags);
204-
staticvoidReleaseDeletionLock(constObjectAddress*object);
205203
staticboolfind_expr_references_walker(Node*node,
206204
find_expr_references_context*context);
207205
staticvoideliminate_duplicate_dependencies(ObjectAddresses*addrs);
@@ -1527,11 +1525,14 @@ doDeletion(const ObjectAddress *object, int flags)
15271525
/*
15281526
* AcquireDeletionLock - acquire a suitable lock for deleting an object
15291527
*
1528+
* Accepts the same flags as performDeletion (though currently only
1529+
* PERFORM_DELETION_CONCURRENTLY does anything).
1530+
*
15301531
* We use LockRelation for relations, LockDatabaseObject for everything
1531-
* else.Note that dependency.c isnotconcerned with deleting any kind of
1532-
*shared-across-databases object, so we have no need for LockSharedObject.
1532+
* else.Shared-across-databases objects arenotcurrently supported
1533+
*because no caller cares, but could be modified to use LockSharedObject.
15331534
*/
1534-
staticvoid
1535+
void
15351536
AcquireDeletionLock(constObjectAddress*object,intflags)
15361537
{
15371538
if (object->classId==RelationRelationId)
@@ -1557,8 +1558,10 @@ AcquireDeletionLock(const ObjectAddress *object, int flags)
15571558

15581559
/*
15591560
* ReleaseDeletionLock - release an object deletion lock
1561+
*
1562+
* Companion to AcquireDeletionLock.
15601563
*/
1561-
staticvoid
1564+
void
15621565
ReleaseDeletionLock(constObjectAddress*object)
15631566
{
15641567
if (object->classId==RelationRelationId)

‎src/backend/catalog/pg_shdepend.c

Lines changed: 23 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1324,14 +1324,29 @@ shdepDropOwned(List *roleids, DropBehavior behavior)
13241324
sdepForm->objid);
13251325
break;
13261326
caseSHARED_DEPENDENCY_POLICY:
1327-
/* If unable to remove role from policy, remove policy. */
1327+
/*
1328+
* Try to remove role from policy; if unable to, remove
1329+
* policy.
1330+
*/
13281331
if (!RemoveRoleFromObjectPolicy(roleid,
13291332
sdepForm->classid,
13301333
sdepForm->objid))
13311334
{
13321335
obj.classId=sdepForm->classid;
13331336
obj.objectId=sdepForm->objid;
13341337
obj.objectSubId=sdepForm->objsubid;
1338+
/*
1339+
* Acquire lock on object, then verify this dependency
1340+
* is still relevant. If not, the object might have
1341+
* been dropped or the policy modified. Ignore the
1342+
* object in that case.
1343+
*/
1344+
AcquireDeletionLock(&obj,0);
1345+
if (!systable_recheck_tuple(scan,tuple))
1346+
{
1347+
ReleaseDeletionLock(&obj);
1348+
break;
1349+
}
13351350
add_exact_object_address(&obj,deleteobjs);
13361351
}
13371352
break;
@@ -1342,6 +1357,13 @@ shdepDropOwned(List *roleids, DropBehavior behavior)
13421357
obj.classId=sdepForm->classid;
13431358
obj.objectId=sdepForm->objid;
13441359
obj.objectSubId=sdepForm->objsubid;
1360+
/* as above */
1361+
AcquireDeletionLock(&obj,0);
1362+
if (!systable_recheck_tuple(scan,tuple))
1363+
{
1364+
ReleaseDeletionLock(&obj);
1365+
break;
1366+
}
13451367
add_exact_object_address(&obj,deleteobjs);
13461368
}
13471369
break;

‎src/backend/commands/subscriptioncmds.c

Lines changed: 0 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -915,7 +915,6 @@ DropSubscription(DropSubscriptionStmt *stmt, bool isTopLevel)
915915
if (slotname)
916916
PreventInTransactionBlock(isTopLevel,"DROP SUBSCRIPTION");
917917

918-
919918
ObjectAddressSet(myself,SubscriptionRelationId,subid);
920919
EventTriggerSQLDropAddObject(&myself, true, true);
921920

‎src/include/catalog/dependency.h

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -142,6 +142,10 @@ typedef enum ObjectClass
142142

143143
/* in dependency.c */
144144

145+
externvoidAcquireDeletionLock(constObjectAddress*object,intflags);
146+
147+
externvoidReleaseDeletionLock(constObjectAddress*object);
148+
145149
externvoidperformDeletion(constObjectAddress*object,
146150
DropBehaviorbehavior,intflags);
147151

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