While determining the filter clauses for an index scan (either plain

or bitmap), use pred_test to be a little smarter about cases where a
filter clause is logically unnecessary.  This may be overkill for the
plain indexscan case, but it's definitely useful for OR'd bitmap scans.

diff --git a/src/backend/optimizer/path/indxpath.c b/src/backend/optimizer/path/indxpath.c
index f55f7fc..0a39884 100644 (file)
--- a/src/backend/optimizer/path/indxpath.c
+++ b/src/backend/optimizer/path/indxpath.c
@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.178 2005/04/25 01:30:13 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.179 2005/04/25 03:58:29 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -500,8 +500,14 @@ choose_bitmap_and(Query *root, RelOptInfo *rel, List *paths)
         * And we consider an index redundant if all its index conditions were
         * already used by earlier indexes.  (We could use pred_test() to have
         * a more intelligent, but much more expensive, check --- but in most
-        * cases simple equality should suffice, since after all the index
-        * conditions are all coming from the same query clauses.)
+        * cases simple pointer equality should suffice, since after all the
+        * index conditions are all coming from the same RestrictInfo lists.)
+        *
+        * XXX is there any risk of throwing away a useful partial index here
+        * because we don't explicitly look at indpred?  At least in simple
+        * cases, the partial index will sort before competing non-partial
+        * indexes and so it makes the right choice, but perhaps we need to
+        * work harder.
         */
 
        /* Convert list to array so we can apply qsort */
@@ -530,7 +536,7 @@ choose_bitmap_and(Query *root, RelOptInfo *rel, List *paths)
                if (IsA(newpath, IndexPath))
                {
                        newqual = ((IndexPath *) newpath)->indexclauses;
-                       if (list_difference(newqual, qualsofar) == NIL)
+                       if (list_difference_ptr(newqual, qualsofar) == NIL)
                                continue;               /* redundant */
                }
 

diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 8c06278..3feff40 100644 (file)
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/optimizer/plan/createplan.c,v 1.186 2005/04/25 02:14:47 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/optimizer/plan/createplan.c,v 1.187 2005/04/25 03:58:30 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -720,6 +720,7 @@ create_indexscan_plan(Query *root,
        List       *nonlossy_indexquals;
        List       *indexstrategy;
        List       *indexsubtype;
+       ListCell   *l;
        IndexScan  *scan_plan;
 
        /* it should be a base rel... */
@@ -768,13 +769,31 @@ create_indexscan_plan(Query *root,
         * checked (either by the index itself, or by nodeIndexscan.c), but if
         * there are any "special" operators involved then they must be included
         * in qpqual.  Also, any lossy index operators must be rechecked in
-        * the qpqual.  The upshot is that qpquals must contain scan_clauses
+        * the qpqual.  The upshot is that qpqual must contain scan_clauses
         * minus whatever appears in nonlossy_indexquals.
+        *
+        * In normal cases simple pointer equality checks will be enough to
+        * spot duplicate RestrictInfos, so we try that first.  In some situations
+        * (particularly with OR'd index conditions) we may have scan_clauses
+        * that are not equal to, but are logically implied by, the index quals;
+        * so we also try a pred_test() check to see if we can discard quals
+        * that way.
+        *
+        * While at it, we strip off the RestrictInfos to produce a list of
+        * plain expressions.
         */
-       qpqual = list_difference_ptr(scan_clauses, nonlossy_indexquals);
+       qpqual = NIL;
+       foreach(l, scan_clauses)
+       {
+               RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
 
-       /* Reduce RestrictInfo list to bare expressions */
-       qpqual = get_actual_clauses(qpqual);
+               Assert(IsA(rinfo, RestrictInfo));
+               if (list_member_ptr(nonlossy_indexquals, rinfo))
+                       continue;
+               if (pred_test(list_make1(rinfo->clause), nonlossy_indexquals))
+                       continue;
+               qpqual = lappend(qpqual, rinfo->clause);
+       }
 
        /* Sort clauses into best execution order */
        qpqual = order_qual_clauses(root, qpqual);
@@ -813,6 +832,7 @@ create_bitmap_scan_plan(Query *root,
        List       *bitmapqualorig;
        List       *indexquals;
        List       *qpqual;
+       ListCell   *l;
        BitmapHeapScan *scan_plan;
 
        /* it should be a base rel... */
@@ -848,13 +868,23 @@ create_bitmap_scan_plan(Query *root,
         * must be added to qpqual.  The upshot is that qpquals must contain
         * scan_clauses minus whatever appears in indexquals.
         *
-        * NOTE: when there are OR clauses in indexquals, the simple equality
-        * check used by list_difference will only detect matches in case of
-        * chance equality of the OR subclause ordering.  This is probably all
-        * right for now because that order will match what's in scan_clauses
-        * ... but perhaps we need more smarts here.
+        * In normal cases simple equal() checks will be enough to spot duplicate
+        * clauses, so we try that first.  In some situations (particularly with
+        * OR'd index conditions) we may have scan_clauses that are not equal to,
+        * but are logically implied by, the index quals; so we also try a
+        * pred_test() check to see if we can discard quals that way.
         */
-       qpqual = list_difference(scan_clauses, indexquals);
+       qpqual = NIL;
+       foreach(l, scan_clauses)
+       {
+               Node   *clause = (Node *) lfirst(l);
+
+               if (list_member(indexquals, clause))
+                       continue;
+               if (pred_test(list_make1(clause), indexquals))
+                       continue;
+               qpqual = lappend(qpqual, clause);
+       }
 
        /* Sort clauses into best execution order */
        qpqual = order_qual_clauses(root, qpqual);