Make eqsel produce better results for boolean columns,

and make scalarltsel a little more forgiving at the boundaries of the
known range of a column value.

diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c
index 30106744ded9f3e091e5dbbb5260eb3b62f69d3a..6b1f5cde26f1ec44f238985e6825a1d0e4ec2476 100644 (file)
--- a/src/backend/utils/adt/selfuncs.c
+++ b/src/backend/utils/adt/selfuncs.c
@@ -15,7 +15,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.55 2000/02/15 20:49:21 tgl Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.56 2000/02/16 00:59:27 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -144,10 +144,13 @@ eqsel(Oid opid,
                    selec = 1.0 - commonfrac - nullfrac;
                    if (selec > commonfrac)
                        selec = commonfrac;
-                   /* and in fact it's probably less, so apply a fudge
-                    * factor.
+                   /* and in fact it's probably less, so we should apply
+                    * a fudge factor.  The only case where we don't is
+                    * for a boolean column, where indeed we have estimated
+                    * the less-common value's frequency exactly!
                     */
-                   selec *= 0.5;
+                   if (typid != BOOLOID)
+                       selec *= 0.5;
                }
            }
            else
@@ -310,20 +313,20 @@ scalarltsel(Oid opid,
            /* If we trusted the stats fully, we could return a small or
             * large selec depending on which side of the single data point
             * the constant is on.  But it seems better to assume that the
-            * stats are out of date and return a default...
+            * stats are wrong and return a default...
             */
            *result = DEFAULT_INEQ_SEL;
-   }
-       else if (val <= low || val >= high)
+       }
+       else if (val < low || val > high)
        {
            /* If given value is outside the statistical range, return a
             * small or large value; but not 0.0/1.0 since there is a chance
             * the stats are out of date.
             */
            if (flag & SEL_RIGHT)
-               *result = (val <= low) ? 0.01 : 0.99;
+               *result = (val < low) ? 0.001 : 0.999;
            else
-               *result = (val <= low) ? 0.99 : 0.01;
+               *result = (val < low) ? 0.999 : 0.001;
        }
        else
        {