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| author | Tom Lane <tgl@sss.pgh.pa.us> | 1999-08-08 17:13:10 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 1999-08-08 17:13:10 +0000 |
| commit | fb491a5854f6883f38bffac0591c754b475695af (patch) | |
| tree | a7e5fbd1142df454b0522261a9576a6e9c7adeaf | |
| parent | a76ad509fef621719abb95fedb526e9a0092a312 (diff) | |
| download | postgresql-fb491a5854f6883f38bffac0591c754b475695af.tar.gz postgresql-fb491a5854f6883f38bffac0591c754b475695af.zip | |
For a unique-key attribute (no duplicate values), vacuum analyze
was recording a disbursion of 0, not the correct value 1/numberOfRows.
| -rw-r--r-- | src/backend/commands/vacuum.c | 24 |
1 files 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; |