diff options
Diffstat (limited to 'src/backend/utils/adt')
| -rw-r--r-- | src/backend/utils/adt/selfuncs.c | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c index b0f9b2da3d2..a996f0c4939 100644 --- a/src/backend/utils/adt/selfuncs.c +++ b/src/backend/utils/adt/selfuncs.c @@ -4401,9 +4401,10 @@ estimate_hash_bucket_stats(PlannerInfo *root, Node *hashkey, double nbuckets, examine_variable(root, hashkey, 0, &vardata); - /* Look up the frequency of the most common value, if available */ + /* Initialize *mcv_freq to "unknown" */ *mcv_freq = 0.0; + /* Look up the frequency of the most common value, if available */ if (HeapTupleIsValid(vardata.statsTuple)) { if (get_attstatsslot(&sslot, vardata.statsTuple, @@ -4417,6 +4418,17 @@ estimate_hash_bucket_stats(PlannerInfo *root, Node *hashkey, double nbuckets, *mcv_freq = sslot.numbers[0]; free_attstatsslot(&sslot); } + else if (get_attstatsslot(&sslot, vardata.statsTuple, + STATISTIC_KIND_HISTOGRAM, InvalidOid, + 0)) + { + /* + * If there are no recorded MCVs, but we do have a histogram, then + * assume that ANALYZE determined that the column is unique. + */ + if (vardata.rel && vardata.rel->rows > 0) + *mcv_freq = 1.0 / vardata.rel->rows; + } } /* Get number of distinct values */ |