Hi,
The get_parameterized_baserel_size function does not differentiate for
PARTITIONED_REL and always appends the rel's own restriction clauses. However,
for PARTITIONED_REL, rel->tuples is computed in set_append_rel_size which comes
from the sum of lived childrel->rows. It is important to note that
childrel->rows is the estimated number of result tuples, meaning it already
includes the effect of the rel's own restriction clauses.
Therefore, get_parameterized_baserel_size should not append the rel's
own restriction clauses again for PARTITIONED_REL. It seems there might be a
mistake here. Although I have not found any SQL that causes issues, this looks
like a potential problem. The correct code should handle this situation
appropriately like this.
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -5365,7 +5365,10 @@ get_parameterized_baserel_size(PlannerInfo *root,
RelOptInfo *rel,
* restriction clauses. Note that we force the clauses to be treated as
* non-join clauses during selectivity estimation.
*/
- allclauses = list_concat_copy(param_clauses, rel->baserestrictinfo);
+ if (rel->reloptkind == RELOPT_BASEREL && IS_PARTITIONED_REL(rel))
+ allclauses = list_copy(param_clauses);
+ else
+ allclauses = list_concat_copy(param_clauses,
rel->baserestrictinfo);
nrows = rel->tuples *
clauselist_selectivity(root,
allclauses,
Regards,
Yajun Hu
