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

tglsfdc · tglsfdc · commit b71761d2808a · 2000-05-26T17:19:15.000Z
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
@@ -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... */

Original file line number	Diff line number	Diff line change
`@@ -15,7 +15,7 @@`
`15`	`15`	`*`
`16`	`16`	`*`
`17`	`17`	`* IDENTIFICATION`
`18`		`- * $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.65 2000/04/16 04:41:02 tgl Exp $`
	`18`	`+ * $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.66 2000/05/26 17:19:15 tgl Exp $`
`19`	`19`	`*`
`20`	`20`	`*-------------------------------------------------------------------------`
`21`	`21`	`*/`
`@@ -55,6 +55,9 @@`
`55`	`55`	`/* default selectivity estimate for pattern-match operators such as LIKE */`
`56`	`56`	`#define DEFAULT_MATCH_SEL 0.01`
`57`	`57`
	`58`	`+/* "fudge factor" for estimating frequency of not-most-common values */`
	`59`	`+#define NOT_MOST_COMMON_RATIO 0.1`
	`60`	`+`
`58`	`61`	`static bool convert_to_scalar(Datum value, Oid valuetypid, double *scaledvalue,`
`59`	`62`	`Datum lobound, Datum hibound, Oid boundstypid,`
`60`	`63`	`double scaledlobound, double scaledhibound);`
`@@ -190,7 +193,7 @@ eqsel(Oid opid,`
`190`	`193`	`* exactly!`
`191`	`194`	`*/`
`192`	`195`	`if (typid != BOOLOID)`
`193`		`- selec *= 0.5;`
	`196`	`+ selec *= NOT_MOST_COMMON_RATIO;`
`194`	`197`	`}`
`195`	`198`	`}`
`196`	`199`	`else`
`@@ -209,7 +212,7 @@ eqsel(Oid opid,`
`209`	`212`	`* and in fact it's probably less, so apply a fudge`
`210`	`213`	`* factor.`
`211`	`214`	`*/`
`212`		`- selec *= 0.5;`
	`215`	`+ selec *= NOT_MOST_COMMON_RATIO;`
`213`	`216`	`}`
`214`	`217`
`215`	`218`	`/* result should be in range, but make sure... */`