Ensure clause_selectivity() behaves sanely when examining an uplevel Var

or a Var that references a subquery output.

diff --git a/src/backend/optimizer/path/clausesel.c b/src/backend/optimizer/path/clausesel.c
index 7d80e288199298fc2bd3fca3d4d73265ebb743ef..dc2448e15a880bb1f3c6b2a11620d3c9ededbd2d 100644 (file)
--- a/src/backend/optimizer/path/clausesel.c
+++ b/src/backend/optimizer/path/clausesel.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/optimizer/path/clausesel.c,v 1.39 2000/08/13 02:50:04 tgl Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/optimizer/path/clausesel.c,v 1.40 2000/10/25 21:48:12 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -371,24 +371,40 @@ clause_selectivity(Query *root,
        return s1;
    if (IsA(clause, Var))
    {
+       Var        *var = (Var *) clause;
 
        /*
-        * we have a bool Var.  This is exactly equivalent to the clause:
-        * reln.attribute = 't' so we compute the selectivity as if that
-        * is what we have. The magic #define constants are a hack.  I
-        * didn't want to have to do system cache look ups to find out all
-        * of that info.
+        * We probably shouldn't ever see an uplevel Var here, but if we
+        * do, return the default selectivity...
         */
-       Index       varno = ((Var *) clause)->varno;
-
-       if (varRelid == 0 || varRelid == (int) varno)
-           s1 = restriction_selectivity(F_EQSEL,
-                                        BooleanEqualOperator,
-                                        getrelid(varno, root->rtable),
-                                        ((Var *) clause)->varattno,
-                                        BoolGetDatum(true),
-                                        SEL_CONSTANT | SEL_RIGHT);
-       /* an outer-relation bool var is taken as always true... */
+       if (var->varlevelsup == 0 &&
+           (varRelid == 0 || varRelid == (int) var->varno))
+       {
+           RangeTblEntry *rte = rt_fetch(var->varno, root->rtable);
+
+           if (rte->subquery)
+           {
+               /*
+                * XXX not smart about subquery references...
+                * any way to do better?
+                */
+               s1 = 0.5;
+           }
+           else
+           {
+               /*
+                * A Var at the top of a clause must be a bool Var.
+                * This is equivalent to the clause reln.attribute = 't',
+                * so we compute the selectivity as if that is what we have.
+                */
+               s1 = restriction_selectivity(F_EQSEL,
+                                            BooleanEqualOperator,
+                                            rte->relid,
+                                            var->varattno,
+                                            BoolGetDatum(true),
+                                            SEL_CONSTANT | SEL_RIGHT);
+           }
+       }
    }
    else if (IsA(clause, Param))
    {