Now that hashjoin is reliable for large joins (knock on wood),

remove optimizer's arbitrary limit on how large a join it will use hashing
for.  (The limit was too large to prevent the problems we'd been seeing,
anyway...)

diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c
index 930112f..9bb890c 100644 (file)
--- a/src/backend/optimizer/path/joinpath.c
+++ b/src/backend/optimizer/path/joinpath.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *       $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinpath.c,v 1.35 1999/05/16 19:45:37 tgl Exp $
+ *       $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinpath.c,v 1.36 1999/05/18 21:36:10 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -37,7 +37,6 @@ static List *match_unsorted_outer(RelOptInfo *joinrel, RelOptInfo *outerrel, Rel
                                         List *mergeinfo_list);
 static List *match_unsorted_inner(RelOptInfo *joinrel, RelOptInfo *outerrel, RelOptInfo *innerrel,
                                         List *innerpath_list, List *mergeinfo_list);
-static bool EnoughMemoryForHashjoin(RelOptInfo *hashrel);
 static List *hash_inner_and_outer(RelOptInfo *joinrel, RelOptInfo *outerrel, RelOptInfo *innerrel,
                                         List *hashinfo_list);
 
@@ -490,27 +489,6 @@ match_unsorted_inner(RelOptInfo *joinrel,
        return mp_list;
 }
 
-static bool
-EnoughMemoryForHashjoin(RelOptInfo *hashrel)
-{
-       int                     ntuples;
-       int                     tupsize;
-       int                     pages;
-
-       ntuples = hashrel->size;
-       if (ntuples == 0)
-               ntuples = 1000;
-       tupsize = hashrel->width + sizeof(HeapTupleData);
-       pages = page_size(ntuples, tupsize);
-
-       /*
-        * if amount of buffer space below hashjoin threshold, return false
-        */
-       if (ceil(sqrt((double) pages)) > NBuffers)
-               return false;
-       return true;
-}
-
 /*
  * hash_inner_and_outer--                              XXX HASH
  *       Create hashjoin join paths by explicitly hashing both the outer and
@@ -530,17 +508,17 @@ hash_inner_and_outer(RelOptInfo *joinrel,
                                         RelOptInfo *innerrel,
                                         List *hashinfo_list)
 {
-       HashInfo   *xhashinfo = (HashInfo *) NULL;
        List       *hjoin_list = NIL;
-       HashPath   *temp_node = (HashPath *) NULL;
-       List       *i = NIL;
-       List       *outerkeys = NIL;
-       List       *innerkeys = NIL;
-       List       *hash_pathkeys = NIL;
+       List       *i;
 
        foreach(i, hashinfo_list)
        {
-               xhashinfo = (HashInfo *) lfirst(i);
+               HashInfo   *xhashinfo = (HashInfo *) lfirst(i);
+               List       *outerkeys;
+               List       *innerkeys;
+               List       *hash_pathkeys;
+               HashPath   *temp_node;
+
                outerkeys = make_pathkeys_from_joinkeys(
                                                          ((JoinMethod *) xhashinfo)->jmkeys,
                                                          outerrel->targetlist,
@@ -549,26 +527,31 @@ hash_inner_and_outer(RelOptInfo *joinrel,
                                                          ((JoinMethod *) xhashinfo)->jmkeys,
                                                          innerrel->targetlist,
                                                          INNER);
+               /* We cannot assume that the output of the hashjoin appears in any
+                * particular order, so it should have NIL pathkeys.
+                */
+#ifdef NOT_USED
                hash_pathkeys = new_join_pathkeys(outerkeys,
                                                          joinrel->targetlist,
                                                          ((JoinMethod *) xhashinfo)->clauses);
-
-               if (EnoughMemoryForHashjoin(innerrel))
-               {
-                       temp_node = create_hashjoin_path(joinrel,
-                                                                                        outerrel->size,
-                                                                                        innerrel->size,
-                                                                                        outerrel->width,
-                                                                                        innerrel->width,
-                                                                                       (Path *) outerrel->cheapestpath,
-                                                                                       (Path *) innerrel->cheapestpath,
-                                                                                        hash_pathkeys,
-                                                                                        xhashinfo->hashop,
-                                                                               ((JoinMethod *) xhashinfo)->clauses,
-                                                                                        outerkeys,
-                                                                                        innerkeys);
-                       hjoin_list = lappend(hjoin_list, temp_node);
-               }
+#else
+               hash_pathkeys = NIL;
+#endif
+
+               temp_node = create_hashjoin_path(joinrel,
+                                                                                outerrel->size,
+                                                                                innerrel->size,
+                                                                                outerrel->width,
+                                                                                innerrel->width,
+                                                                                (Path *) outerrel->cheapestpath,
+                                                                                (Path *) innerrel->cheapestpath,
+                                                                                hash_pathkeys,
+                                                                                xhashinfo->hashop,
+                                                                                ((JoinMethod *) xhashinfo)->clauses,
+                                                                                outerkeys,
+                                                                                innerkeys);
+               hjoin_list = lappend(hjoin_list, temp_node);
        }
+
        return hjoin_list;
 }