Rules: 2nd patch - Mailing list pgsql-hackers

Hi,

    here's  the  second  patch  for the rule system. It fixes the
    backend crashes that occur when using views/rules in the same
    session  where  they  are  created.  The bug was that the new
    actions parsetrees and event  qualifications,  added  to  the
    relations  rd_rules  locks,  where  not  copied  to the cache
    memory context.

    In addition it prepares  tcop/postgres.c  to  handle  a  zero
    length  rewritten  list  returned by QueryRewrite() correctly
    (due to instead nothing).

    Next patch will allow instead  nothing  on  select  rules  to
    return  no  tuples at all instead of one with all NULL fields
    (as it is now).


Jan

--

#======================================================================#
# It's easier to get forgiveness for being wrong than for being right. #
# Let's break this rule - forgive me.                                  #
#======================================== jwieck@debis.com (Jan Wieck) #


diff -cr backend.orig/rewrite/rewriteSupport.c backend/rewrite/rewriteSupport.c
*** backend.orig/rewrite/rewriteSupport.c    Wed Aug 19 10:36:15 1998
--- backend/rewrite/rewriteSupport.c    Wed Aug 19 10:55:03 1998
***************
*** 158,163 ****
--- 158,167 ----
       */
      oldcxt = MemoryContextSwitchTo((MemoryContext) CacheCxt);
      thisRule = (RewriteRule *) palloc(sizeof(RewriteRule));
+     if (qual != NULL)
+         qual = copyObject(qual);
+     if (actions != NIL)
+         actions = copyObject(actions);
      MemoryContextSwitchTo(oldcxt);

      thisRule->ruleId = ruleId;
diff -cr backend.orig/tcop/postgres.c backend/tcop/postgres.c
*** backend.orig/tcop/postgres.c    Fri Aug  7 11:05:41 1998
--- backend/tcop/postgres.c    Wed Aug 19 10:51:50 1998
***************
*** 451,474 ****
          /* rewrite queries (retrieve, append, delete, replace) */
          rewritten = QueryRewrite(querytree);

!         /*
!          * Rewrite the UNIONS.
!          */
!         foreach(rewritten_list, rewritten)
!         {
!             Query       *qry = (Query *) lfirst(rewritten_list);
!
!             union_result = NIL;
!             foreach(union_list, qry->unionClause)
!                 union_result = nconc(union_result, QueryRewrite((Query *) lfirst(union_list)));
!             qry->unionClause = union_result;
!         }
!
!         if (rewritten != NULL)
          {
              int            len,
                          k;

              len = length(rewritten);
              if (len == 1)
                  new_list->qtrees[j++] = (Query *) lfirst(rewritten);
--- 451,474 ----
          /* rewrite queries (retrieve, append, delete, replace) */
          rewritten = QueryRewrite(querytree);

!         if (rewritten != NIL)
          {
              int            len,
                          k;

+             /*
+              * Rewrite the UNIONS.
+              */
+             foreach(rewritten_list, rewritten)
+             {
+                 Query       *qry = (Query *) lfirst(rewritten_list);
+
+                 union_result = NIL;
+                 foreach(union_list, qry->unionClause)
+                     union_result = nconc(union_result, QueryRewrite((Query *) lfirst(union_list)));
+                 qry->unionClause = union_result;
+             }
+
              len = length(rewritten);
              if (len == 1)
                  new_list->qtrees[j++] = (Query *) lfirst(rewritten);
***************
*** 487,492 ****
--- 487,500 ----
          }
      }

+     /* ----------
+      * Due to rewriting, the new list could also have been
+      * shrunk (do instead nothing). Forget obsolete queries
+      * at the end.
+      * ----------
+      */
+     new_list->len = j;
+
      /* we're done with the original lists, free it */
      free(querytree_list->qtrees);
      free(querytree_list);
***************
*** 530,536 ****
                  elog(NOTICE, "(transaction aborted): %s",
                       "queries ignored until END");

!                 *queryListP = (QueryTreeList *) NULL;
                  return (List *) NULL;
              }

--- 538,547 ----
                  elog(NOTICE, "(transaction aborted): %s",
                       "queries ignored until END");

!                 free(querytree_list->qtrees);
!                 free(querytree_list);
!                 if (queryListP)
!                     *queryListP = (QueryTreeList *) NULL;
                  return (List *) NULL;
              }

***************
*** 571,576 ****
--- 582,597 ----
          else
              plan_list = lappend(plan_list, NULL);
  #endif
+     }
+
+     /* ----------
+      * Check if the rewriting had thrown away anything
+      * ----------
+      */
+     if (querytree_list->len == 0) {
+         free(querytree_list->qtrees);
+         free(querytree_list);
+         querytree_list = NULL;
      }

      if (queryListP)