Reduce eqsel()'s fudge-factor for estimating the frequency of values

other than the most common value in a column.  We had had 0.5, make it
0.1 to make it more likely that an indexscan will be chosen.  Really
need better statistics instead, but this should stem the bleeding
meanwhile ...

diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c
index a1405602ee4189f5976749b821c17e562795ec61..4718dc668a7313fb5a21d6b50c666f0360acf733 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 1.65 2000/04/16 04:41:02 tgl Exp $
+ *       $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.66 2000/05/26 17:19:15 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -55,6 +55,9 @@
 /* default selectivity estimate for pattern-match operators such as LIKE */
 #define DEFAULT_MATCH_SEL      0.01
 
+/* "fudge factor" for estimating frequency of not-most-common values */
+#define NOT_MOST_COMMON_RATIO  0.1
+
 static bool convert_to_scalar(Datum value, Oid valuetypid, double *scaledvalue,
                                                          Datum lobound, Datum hibound, Oid boundstypid,
                                                          double *scaledlobound, double *scaledhibound);
@@ -190,7 +193,7 @@ eqsel(Oid opid,
                                         * exactly!
                                         */
                                        if (typid != BOOLOID)
-                                               selec *= 0.5;
+                                               selec *= NOT_MOST_COMMON_RATIO;
                                }
                        }
                        else
@@ -209,7 +212,7 @@ eqsel(Oid opid,
                                 * and in fact it's probably less, so apply a fudge
                                 * factor.
                                 */
-                               selec *= 0.5;
+                               selec *= NOT_MOST_COMMON_RATIO;
                        }
 
                        /* result should be in range, but make sure... */