diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/statistics/extended_stats.c | 25 | ||||
| -rw-r--r-- | src/test/regress/expected/stats_ext.out | 2 |
2 files changed, 18 insertions, 9 deletions
diff --git a/src/backend/statistics/extended_stats.c b/src/backend/statistics/extended_stats.c index 8d3cd091ada..555bc325619 100644 --- a/src/backend/statistics/extended_stats.c +++ b/src/backend/statistics/extended_stats.c @@ -1356,17 +1356,19 @@ statext_mcv_clauselist_selectivity(PlannerInfo *root, List *clauses, int varReli if (is_or) { bool *or_matches = NULL; - Selectivity simple_or_sel = 0.0; + Selectivity simple_or_sel = 0.0, + stat_sel = 0.0; MCVList *mcv_list; /* Load the MCV list stored in the statistics object */ mcv_list = statext_mcv_load(stat->statOid); /* - * Compute the selectivity of the ORed list of clauses by - * estimating each in turn and combining them using the formula - * P(A OR B) = P(A) + P(B) - P(A AND B). This allows us to use - * the multivariate MCV stats to better estimate each term. + * Compute the selectivity of the ORed list of clauses covered by + * this statistics object by estimating each in turn and combining + * them using the formula P(A OR B) = P(A) + P(B) - P(A AND B). + * This allows us to use the multivariate MCV stats to better + * estimate the individual terms and their overlap. * * Each time we iterate this formula, the clause "A" above is * equal to all the clauses processed so far, combined with "OR". @@ -1437,12 +1439,19 @@ statext_mcv_clauselist_selectivity(PlannerInfo *root, List *clauses, int varReli overlap_basesel, mcv_totalsel); - /* Factor these into the overall result */ - sel += clause_sel - overlap_sel; - CLAMP_PROBABILITY(sel); + /* Factor these into the result for this statistics object */ + stat_sel += clause_sel - overlap_sel; + CLAMP_PROBABILITY(stat_sel); listidx++; } + + /* + * Factor the result for this statistics object into the overall + * result. We treat the results from each separate statistics + * object as independent of one another. + */ + sel = sel + stat_sel - sel * stat_sel; } else /* Implicitly-ANDed list of clauses */ { diff --git a/src/test/regress/expected/stats_ext.out b/src/test/regress/expected/stats_ext.out index dbbe9844b2e..6e1c4f3edd1 100644 --- a/src/test/regress/expected/stats_ext.out +++ b/src/test/regress/expected/stats_ext.out @@ -1706,7 +1706,7 @@ SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE (a = 0 A SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE a = 0 OR b = 0 OR c = 0 OR d = 0'); estimated | actual -----------+-------- - 1714 | 1572 + 1571 | 1572 (1 row) DROP TABLE mcv_lists_multi; |