Patch for BUG #2073: Can't drop sequence when created via SERIAL column - Mailing list pgsql-patches

Hi

I send the appropriate patch for bug #2073. This fix disallows to change the default sequence.
I ran the regression test and passed. The bug details are given below.
I am awaiting to answer for any further clarifications.

===================================================================
> Bug reference:      2073
> Logged by:          Aaron Dummer
> Email address:      aaron ( at ) dummer ( dot ) info
> PostgreSQL version: 8.0.3
> Operating system:   Debian Linux
> Description:        Can't drop sequence when created via SERIAL column
> Details:
>
> If I create a table named foo with a column named bar, column type SERIAL,
> it auto-generates a sequence named foo_bar_seq.  Now if I manually create a
> new sequence called custom_seq, and change the default value of foo.bar to
> reference the new sequence, I still can't delete the old sequence
> (foo_bar_seq).
>
> In other words, from a user's point of view, the foo table is no longer
> dependent on the foo_bar_seq, yet the system still sees it as dependent.
>
> I brought this topic up on the #postgresql IRC channel and the behavior was
> confirmed by AndrewSN, scampbell_, and mastermind.

Right.  We have this TODO item:

    * %Disallow changing default expression of a SERIAL column?

which would prevent you from changing the default expression for a
SERIAL column.  So the answer is, don't do that, and in the future, we
might prevent it.

--
  Bruce Momjian

==================================================================

*** ./src/backend/catalog/dependency.c.orig    Wed Apr 26 10:54:40 2006
--- ./src/backend/catalog/dependency.c    Wed Apr 26 12:09:01 2006
***************
*** 1931,1933 ****
--- 1931,2019 ----

      ReleaseSysCache(relTup);
  }
+
+ /* Recursively travel and search for the default sequence. Finally detach it */
+
+ void performSequenceDefaultDeletion(const ObjectAddress *object,
+                     DropBehavior behavior, int deleteFlag)
+ {
+
+         ScanKeyData key[3];
+         int                     nkeys;
+         SysScanDesc scan;
+         HeapTuple       tup;
+         ObjectAddress otherObject;
+       Relation    depRel;
+
+       depRel = heap_open(DependRelationId, RowExclusiveLock);
+
+         ScanKeyInit(&key[0],
+                                 Anum_pg_depend_classid,
+                                 BTEqualStrategyNumber, F_OIDEQ,
+                                 ObjectIdGetDatum(object->classId));
+         ScanKeyInit(&key[1],
+                                 Anum_pg_depend_objid,
+                                 BTEqualStrategyNumber, F_OIDEQ,
+                                 ObjectIdGetDatum(object->objectId));
+         if (object->objectSubId != 0)
+         {
+                ScanKeyInit(&key[2],
+                                         Anum_pg_depend_objsubid,
+                                         BTEqualStrategyNumber, F_INT4EQ,
+                                         Int32GetDatum(object->objectSubId));
+                 nkeys = 3;
+         }
+         else
+                 nkeys = 2;
+
+         scan = systable_beginscan(depRel, DependDependerIndexId, true,
+                                                           SnapshotNow, nkeys, key);
+
+         while (HeapTupleIsValid(tup = systable_getnext(scan)))
+         {
+
+                 Form_pg_depend foundDep = (Form_pg_depend) GETSTRUCT(tup);
+
+                 otherObject.classId = foundDep->refclassid;
+                 otherObject.objectId = foundDep->refobjid;
+                 otherObject.objectSubId = foundDep->refobjsubid;
+
+           /* Detach the default sequence from the relation */
+           if(deleteFlag == 1)
+           {
+                     simple_heap_delete(depRel, &tup->t_self);
+             break;
+           }
+
+                 switch (foundDep->deptype)
+                 {
+                         case DEPENDENCY_NORMAL:
+             {
+
+                 if(getObjectClass(&otherObject) == OCLASS_CLASS)
+                 {
+                     /* Dont allow to change the default sequence */
+                     if(deleteFlag == 2)
+                     {
+                         systable_endscan(scan);
+                                 heap_close(depRel, RowExclusiveLock);
+                                             elog(ERROR, "%s is a SERIAL sequence. Can't alter the relation",
getObjectDescription(&otherObject));
+                                             return;
+                     }
+                     else /* Detach the default sequence from the relation */
+                     {
+                         performSequenceDefaultDeletion(&otherObject, behavior, 1);
+                         systable_endscan(scan);
+                         heap_close(depRel, RowExclusiveLock);
+                                             return;
+                     }
+                 }
+             }
+
+             }
+     }
+
+         systable_endscan(scan);
+     heap_close(depRel, RowExclusiveLock);
+
+ }
*** ./src/backend/catalog/heap.c.orig    Wed Apr 26 10:59:18 2006
--- ./src/backend/catalog/heap.c    Wed Apr 26 12:03:49 2006
***************
*** 2136,2138 ****
--- 2136,2185 ----

      return result;
  }
+
+
+ /* Detach the default sequence and the relation */
+
+ void
+ RemoveSequenceDefault(Oid relid, AttrNumber attnum,
+                   DropBehavior behavior, bool flag)
+ {
+     Relation    attrdef_rel;
+     ScanKeyData scankeys[2];
+     SysScanDesc scan;
+     HeapTuple    tuple;
+
+     attrdef_rel = heap_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,
+                               SnapshotNow, 2, scankeys);
+
+     /* There should be at most one matching tuple, but we loop anyway */
+     while (HeapTupleIsValid(tuple = systable_getnext(scan)))
+     {
+         ObjectAddress object;
+
+         object.classId = AttrDefaultRelationId;
+         object.objectId = HeapTupleGetOid(tuple);
+         object.objectSubId = 0;
+
+         if(flag == true) /* Detach the sequence */
+               performSequenceDefaultDeletion(&object, behavior, 0);
+         else    /* Don't allow to change the default sequence */
+             performSequenceDefaultDeletion(&object, behavior, 2);
+
+     }
+
+     systable_endscan(scan);
+     heap_close(attrdef_rel, RowExclusiveLock);
+
+ }
*** ./src/backend/commands/tablecmds.c.orig    Wed Apr 26 11:00:14 2006
--- ./src/backend/commands/tablecmds.c    Wed Apr 26 11:57:43 2006
***************
*** 3362,3367 ****
--- 3362,3372 ----
       * safety, but at present we do not expect anything to depend on the
       * default.
       */
+     if (newDefault)
+         RemoveSequenceDefault(RelationGetRelid(rel), attnum, DROP_RESTRICT, false);
+     else
+         RemoveSequenceDefault(RelationGetRelid(rel), attnum, DROP_RESTRICT, true);
+
      RemoveAttrDefault(RelationGetRelid(rel), attnum, DROP_RESTRICT, false);

      if (newDefault)
*** ./src/include/catalog/dependency.h.orig    Wed Apr 26 11:05:28 2006
--- ./src/include/catalog/dependency.h    Wed Apr 26 11:06:13 2006
***************
*** 207,210 ****
--- 207,213 ----

  extern void shdepReassignOwned(List *relids, Oid newrole);

+ extern void performSequenceDefaultDeletion(const ObjectAddress *object,
+                     DropBehavior behavior, int deleteFlag);
+
  #endif   /* DEPENDENCY_H */
*** ./src/include/catalog/heap.h.orig    Wed Apr 26 11:04:59 2006
--- ./src/include/catalog/heap.h    Wed Apr 26 11:57:56 2006
***************
*** 97,100 ****
--- 97,103 ----

  extern void CheckAttributeType(const char *attname, Oid atttypid);

+ extern void RemoveSequenceDefault(Oid relid, AttrNumber attnum,
+                   DropBehavior behavior, bool flag);
+
  #endif   /* HEAP_H */