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For a unique-key attribute (no duplicate values), vacuum analyze

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was recording a disbursion of 0, not the correct value 1/numberOfRows.
This commit is contained in:
Tom Lane 1999-08-08 17:13:10 +00:00
parent a76ad509fe
commit fb491a5854
1 changed files with 16 additions and 8 deletions
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24
src/backend/commands/vacuum.c
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@ -7,7 +7,7 @@
* *
* *
* IDENTIFICATION * 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 */ /* overwrite the existing statistics in the tuple */
if (VacAttrStatsEqValid(stats)) if (VacAttrStatsEqValid(stats))
{ {
if (stats->nonnull_cnt + stats->null_cnt == 0 || if (stats->nonnull_cnt == 0 && stats->null_cnt == 0)
(stats->null_cnt <= 1 && stats->best_cnt == 1)) {
/* empty relation, so put a dummy value in attdisbursion */
selratio = 0; 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) else if (VacAttrStatsLtGtValid(stats) && stats->min_cnt + stats->max_cnt == stats->nonnull_cnt)
{ {
/* exact result when there are just 1 or 2 values... */ /* exact result when there are just 1 or 2 values... */
double min_cnt_d = stats->min_cnt, double min_cnt_d = stats->min_cnt,
max_cnt_d = stats->max_cnt, max_cnt_d = stats->max_cnt,
null_cnt_d = stats->null_cnt, null_cnt_d = stats->null_cnt;
nonnull_cnt_d = stats->nonnull_cnt; /* prevent overflow */ 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) / selratio = (min_cnt_d * min_cnt_d + max_cnt_d * max_cnt_d + null_cnt_d * null_cnt_d) / (total * total);
(nonnull_cnt_d + null_cnt_d) / (nonnull_cnt_d + null_cnt_d);
} }
else 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 * we assume count of other values are 20% of best
* count in table * 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) if (selratio < 0.0)
selratio = 0.0; selratio = 0.0;