RemoveAttrDefaultById() neglected to obtain exclusive lock on the

relation being modified.  In most paths of control we'd already have
such a lock, but if we were dropping the default due to a cascaded
delete of some function it depended on, maybe not.

diff --git a/src/backend/catalog/heap.c b/src/backend/catalog/heap.c
index ec9165c55b18cb0f05e14f6f6988111bf435b68c..cb1248caaa0cc606584b8924a0410110ccd652a6 100644 (file)
--- a/src/backend/catalog/heap.c
+++ b/src/backend/catalog/heap.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/catalog/heap.c,v 1.215 2002/08/02 18:15:05 tgl Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/catalog/heap.c,v 1.216 2002/08/02 21:54:34 tgl Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -1027,6 +1027,7 @@ RemoveAttrDefaultById(Oid attrdefId)
 {
    Relation    attrdef_rel;
    Relation    attr_rel;
+   Relation    myrel;
    ScanKeyData scankeys[1];
    SysScanDesc scan;
    HeapTuple   tuple;
@@ -1036,6 +1037,7 @@ RemoveAttrDefaultById(Oid attrdefId)
    /* Grab an appropriate lock on the pg_attrdef relation */
    attrdef_rel = heap_openr(AttrDefaultRelationName, RowExclusiveLock);
 
+   /* Find the pg_attrdef tuple */
    ScanKeyEntryInitialize(&scankeys[0], 0x0,
                           ObjectIdAttributeNumber, F_OIDEQ,
                           ObjectIdGetDatum(attrdefId));
@@ -1051,6 +1053,10 @@ RemoveAttrDefaultById(Oid 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 = heap_open(myrelid, AccessExclusiveLock);
+
+   /* Now we can delete the pg_attrdef row */
    simple_heap_delete(attrdef_rel, &tuple->t_self);
 
    systable_endscan(scan);
@@ -1081,7 +1087,14 @@ RemoveAttrDefaultById(Oid attrdefId)
        CatalogCloseIndices(Num_pg_attr_indices, idescs);
    }
 
+   /*
+    * Our update of the pg_attribute row will force a relcache rebuild,
+    * so there's nothing else to do here.
+    */
    heap_close(attr_rel, RowExclusiveLock);
+
+   /* Keep lock on attribute's rel until end of xact */
+   heap_close(myrel, NoLock);
 }
 
 /* ----------------------------------------------------------------