Adjust setRelhassubclassInRelation() to not perform actual heap_update

when the pg_class.relhassubclass value is already correct.  This should
avoid most cases of the 'tuple concurrently updated' problem that
Robert Creager recently complained about.  Also remove a bunch of dead
code in StoreCatalogInheritance() --- it was still computing the complete
list of direct and indirect inheritance ancestors, though that list has
not been needed since we got rid of the pg_ipl catalog.

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 41760f39b97cbfeb1a6c18d59ae9c39df480087c..f0550ff7acd0d64a93c4afc4dc79e73ffad5b448 100644 (file)
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/commands/tablecmds.c,v 1.89 2003/10/12 23:19:21 momjian Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/commands/tablecmds.c,v 1.90 2003/10/13 20:02:52 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -47,6 +47,7 @@
 #include "utils/acl.h"
 #include "utils/builtins.h"
 #include "utils/fmgroids.h"
+#include "utils/inval.h"
 #include "utils/lsyscache.h"
 #include "utils/relcache.h"
 #include "utils/syscache.h"
@@ -558,7 +559,6 @@ MergeAttributes(List *schema, List *supers, bool istemp,
                            parent->relname)));
 
        parentOids = lappendo(parentOids, RelationGetRelid(relation));
-       setRelhassubclassInRelation(RelationGetRelid(relation), true);
 
        parentHasOids |= relation->rd_rel->relhasoids;
 
@@ -869,7 +869,6 @@ change_varattnos_of_a_node(Node *node, const AttrNumber *newattno)
  *     Updates the system catalogs with proper inheritance information.
  *
  * supers is a list of the OIDs of the new relation's direct ancestors.
- * NB: it is destructively changed to include indirect ancestors.
  */
 static void
 StoreCatalogInheritance(Oid relationId, List *supers)
@@ -890,7 +889,12 @@ StoreCatalogInheritance(Oid relationId, List *supers)
 
    /*
     * Store INHERITS information in pg_inherits using direct ancestors
-    * only. Also enter dependencies on the direct ancestors.
+    * only. Also enter dependencies on the direct ancestors, and make sure
+    * they are marked with relhassubclass = true.
+    *
+    * (Once upon a time, both direct and indirect ancestors were found here
+    * and then entered into pg_ipl.  Since that catalog doesn't exist anymore,
+    * there's no need to look for indirect ancestors.)
     */
    relation = heap_openr(InheritsRelationName, RowExclusiveLock);
    desc = RelationGetDescr(relation);
@@ -898,14 +902,14 @@ StoreCatalogInheritance(Oid relationId, List *supers)
    seqNumber = 1;
    foreach(entry, supers)
    {
-       Oid         entryOid = lfirsto(entry);
+       Oid         parentOid = lfirsto(entry);
        Datum       datum[Natts_pg_inherits];
        char        nullarr[Natts_pg_inherits];
        ObjectAddress childobject,
                    parentobject;
 
        datum[0] = ObjectIdGetDatum(relationId);        /* inhrel */
-       datum[1] = ObjectIdGetDatum(entryOid);  /* inhparent */
+       datum[1] = ObjectIdGetDatum(parentOid); /* inhparent */
        datum[2] = Int16GetDatum(seqNumber);    /* inhseqno */
 
        nullarr[0] = ' ';
@@ -924,7 +928,7 @@ StoreCatalogInheritance(Oid relationId, List *supers)
         * Store a dependency too
         */
        parentobject.classId = RelOid_pg_class;
-       parentobject.objectId = entryOid;
+       parentobject.objectId = parentOid;
        parentobject.objectSubId = 0;
        childobject.classId = RelOid_pg_class;
        childobject.objectId = relationId;
@@ -932,85 +936,15 @@ StoreCatalogInheritance(Oid relationId, List *supers)
 
        recordDependencyOn(&childobject, &parentobject, DEPENDENCY_NORMAL);
 
+       /*
+        * Mark the parent as having subclasses.
+        */
+       setRelhassubclassInRelation(parentOid, true);
+
        seqNumber += 1;
    }
 
    heap_close(relation, RowExclusiveLock);
-
-   /* ----------------
-    * Expand supers list to include indirect ancestors as well.
-    *
-    * Algorithm:
-    *  0. begin with list of direct superclasses.
-    *  1. append after each relationId, its superclasses, recursively.
-    *  2. remove all but last of duplicates.
-    * ----------------
-    */
-
-   /*
-    * 1. append after each relationId, its superclasses, recursively.
-    */
-   foreach(entry, supers)
-   {
-       Oid         id = lfirsto(entry);
-       HeapTuple   tuple;
-       int16       number;
-       List       *current;
-       List       *next;
-
-       current = entry;
-       next = lnext(entry);
-
-       for (number = 1;; number += 1)
-       {
-           tuple = SearchSysCache(INHRELID,
-                                  ObjectIdGetDatum(id),
-                                  Int16GetDatum(number),
-                                  0, 0);
-           if (!HeapTupleIsValid(tuple))
-               break;
-
-           lnext(current) = lconso(((Form_pg_inherits)
-                                    GETSTRUCT(tuple))->inhparent,
-                                   NIL);
-           current = lnext(current);
-
-           ReleaseSysCache(tuple);
-       }
-       lnext(current) = next;
-   }
-
-   /*
-    * 2. remove all but last of duplicates.
-    */
-   foreach(entry, supers)
-   {
-       Oid         thisone;
-       bool        found;
-       List       *rest;
-
-again:
-       found = false;
-       thisone = lfirsto(entry);
-       foreach(rest, lnext(entry))
-       {
-           if (thisone == lfirsto(rest))
-           {
-               found = true;
-               break;
-           }
-       }
-       if (found)
-       {
-           /*
-            * found a later duplicate, so remove this entry.
-            */
-           lfirsto(entry) = lfirsto(lnext(entry));
-           lnext(entry) = lnext(lnext(entry));
-
-           goto again;
-       }
-   }
 }
 
 /*
@@ -1044,9 +978,14 @@ setRelhassubclassInRelation(Oid relationId, bool relhassubclass)
 {
    Relation    relationRelation;
    HeapTuple   tuple;
+   Form_pg_class classtuple;
 
    /*
     * Fetch a modifiable copy of the tuple, modify it, update pg_class.
+    *
+    * If the tuple already has the right relhassubclass setting, we
+    * don't need to update it, but we still need to issue an SI inval
+    * message.
     */
    relationRelation = heap_openr(RelationRelationName, RowExclusiveLock);
    tuple = SearchSysCacheCopy(RELOID,
@@ -1054,12 +993,21 @@ setRelhassubclassInRelation(Oid relationId, bool relhassubclass)
                               0, 0, 0);
    if (!HeapTupleIsValid(tuple))
        elog(ERROR, "cache lookup failed for relation %u", relationId);
+   classtuple = (Form_pg_class) GETSTRUCT(tuple);
 
-   ((Form_pg_class) GETSTRUCT(tuple))->relhassubclass = relhassubclass;
-   simple_heap_update(relationRelation, &tuple->t_self, tuple);
+   if (classtuple->relhassubclass != relhassubclass)
+   {
+       classtuple->relhassubclass = relhassubclass;
+       simple_heap_update(relationRelation, &tuple->t_self, tuple);
 
-   /* keep the catalog indexes up to date */
-   CatalogUpdateIndexes(relationRelation, tuple);
+       /* keep the catalog indexes up to date */
+       CatalogUpdateIndexes(relationRelation, tuple);
+   }
+   else
+   {
+       /* no need to change tuple, but force relcache rebuild anyway */
+       CacheInvalidateRelcache(relationId);
+   }
 
    heap_freetuple(tuple);
    heap_close(relationRelation, RowExclusiveLock);