Fix ALTER COLUMN TYPE bug: it sometimes tried to drop UNIQUE or PRIMARY KEY

constraints before FOREIGN KEY constraints that depended on them.  Originally
reported by Neil Conway on 29-Jun-2005.  Patch by Nakano Yoshihisa.

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 20c6437897aa40868319d18814a6999fdfa62196..bc28c5968319a91857a04e92dd85684141606fc2 100644 (file)
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.142.4.4 2005/10/03 02:45:25 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.142.4.5 2006/01/30 16:19:12 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -4926,12 +4926,38 @@ ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
 
                        case OCLASS_CONSTRAINT:
                                Assert(foundObject.objectSubId == 0);
-                               if (!list_member_oid(tab->changedConstraintOids, foundObject.objectId))
+                               if (!list_member_oid(tab->changedConstraintOids,
+                                                                        foundObject.objectId))
                                {
-                                       tab->changedConstraintOids = lappend_oid(tab->changedConstraintOids,
-                                                                                                  foundObject.objectId);
-                                       tab->changedConstraintDefs = lappend(tab->changedConstraintDefs,
-                                         pg_get_constraintdef_string(foundObject.objectId));
+                                       char *defstring = pg_get_constraintdef_string(foundObject.objectId);
+
+                                       /*
+                                        * Put NORMAL dependencies at the front of the list and
+                                        * AUTO dependencies at the back.  This makes sure that
+                                        * foreign-key constraints depending on this column will
+                                        * be dropped before unique or primary-key constraints of
+                                        * the column; which we must have because the FK
+                                        * constraints depend on the indexes belonging to the
+                                        * unique constraints.
+                                        */
+                                       if (foundDep->deptype == DEPENDENCY_NORMAL)
+                                       {
+                                               tab->changedConstraintOids =
+                                                       lcons_oid(foundObject.objectId,
+                                                                         tab->changedConstraintOids);
+                                               tab->changedConstraintDefs =
+                                                       lcons(defstring,
+                                                                 tab->changedConstraintDefs);
+                                       }
+                                       else
+                                       {
+                                               tab->changedConstraintOids =
+                                                       lappend_oid(tab->changedConstraintOids,
+                                                                               foundObject.objectId);
+                                               tab->changedConstraintDefs =
+                                                       lappend(tab->changedConstraintDefs,
+                                                                       defstring);
+                                       }
                                }
                                break;
 
@@ -5099,10 +5125,12 @@ ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab)
                ATPostAlterTypeParse((char *) lfirst(l), wqueue);
 
        /*
-        * Now we can drop the existing constraints and indexes ---
-        * constraints first, since some of them might depend on the indexes.
-        * It should be okay to use DROP_RESTRICT here, since nothing else
-        * should be depending on these objects.
+        * Now we can drop the existing constraints and indexes --- constraints
+        * first, since some of them might depend on the indexes.  In fact, we
+        * have to delete FOREIGN KEY constraints before UNIQUE constraints,
+        * but we already ordered the constraint list to ensure that would happen.
+        * It should be okay to use DROP_RESTRICT here, since nothing else should
+        * be depending on these objects.
         */
        if (tab->changedConstraintOids)
                obj.classId = get_system_catalog_relid(ConstraintRelationName);