From fb491a5854f6883f38bffac0591c754b475695af Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sun, 8 Aug 1999 17:13:10 +0000
Subject: [PATCH] For a unique-key attribute (no duplicate values), vacuum
analyze was recording a disbursion of 0, not the correct value
1/numberOfRows.
---
src/backend/commands/vacuum.c | 24 ++++++++++++++++--------
1 file changed, 16 insertions(+), 8 deletions(-)
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index 12d2bc9bf99..0418a8d3a38 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.116 1999/08/01 04:54:24 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.117 1999/08/08 17:13:10 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -2339,19 +2339,27 @@ vc_updstats(Oid relid, int num_pages, int num_tuples, bool hasindex, VRelStats *
/* overwrite the existing statistics in the tuple */
if (VacAttrStatsEqValid(stats))
{
- if (stats->nonnull_cnt + stats->null_cnt == 0 ||
- (stats->null_cnt <= 1 && stats->best_cnt == 1))
+ if (stats->nonnull_cnt == 0 && stats->null_cnt == 0)
+ {
+ /* empty relation, so put a dummy value in attdisbursion */
selratio = 0;
+ }
+ else if (stats->null_cnt <= 1 && stats->best_cnt == 1)
+ {
+ /* looks like we have a unique-key attribute */
+ double total = ((double) stats->nonnull_cnt) + ((double) stats->null_cnt);
+
+ selratio = 1.0 / total;
+ }
else if (VacAttrStatsLtGtValid(stats) && stats->min_cnt + stats->max_cnt == stats->nonnull_cnt)
{
/* exact result when there are just 1 or 2 values... */
double min_cnt_d = stats->min_cnt,
max_cnt_d = stats->max_cnt,
- null_cnt_d = stats->null_cnt,
- nonnull_cnt_d = stats->nonnull_cnt; /* prevent overflow */
+ null_cnt_d = stats->null_cnt;
+ double total = ((double) stats->nonnull_cnt) + null_cnt_d;
- selratio = (min_cnt_d * min_cnt_d + max_cnt_d * max_cnt_d + null_cnt_d * null_cnt_d) /
- (nonnull_cnt_d + null_cnt_d) / (nonnull_cnt_d + null_cnt_d);
+ selratio = (min_cnt_d * min_cnt_d + max_cnt_d * max_cnt_d + null_cnt_d * null_cnt_d) / (total * total);
}
else
{
@@ -2362,7 +2370,7 @@ vc_updstats(Oid relid, int num_pages, int num_tuples, bool hasindex, VRelStats *
* we assume count of other values are 20% of best
* count in table
*/
- selratio = (most * most + 0.20 * most * (total - most)) / total / total;
+ selratio = (most * most + 0.20 * most * (total - most)) / (total * total);
}
if (selratio < 0.0)
selratio = 0.0;
--
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