diff options
Diffstat (limited to 'src/backend/optimizer/path/costsize.c')
| -rw-r--r-- | src/backend/optimizer/path/costsize.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c index 480c1b7425c..875c611ab50 100644 --- a/src/backend/optimizer/path/costsize.c +++ b/src/backend/optimizer/path/costsize.c @@ -2958,6 +2958,13 @@ cost_qual_eval_walker(Node *node, cost_qual_eval_context *context) * to expect that the current ordering of the clauses is the one that's * going to end up being used. The above per-RestrictInfo caching would * not mix well with trying to re-order clauses anyway. + * + * Another issue that is entirely ignored here is that if a set-returning + * function is below top level in the tree, the functions/operators above + * it will need to be evaluated multiple times. In practical use, such + * cases arise so seldom as to not be worth the added complexity needed; + * moreover, since our rowcount estimates for functions tend to be pretty + * phony, the results would also be pretty phony. */ if (IsA(node, FuncExpr)) { @@ -3742,7 +3749,7 @@ set_function_size_estimates(PlannerInfo *root, RelOptInfo *rel) Assert(rte->rtekind == RTE_FUNCTION); /* Estimate number of rows the function itself will return */ - rel->tuples = clamp_row_est(expression_returns_set_rows(rte->funcexpr)); + rel->tuples = expression_returns_set_rows(rte->funcexpr); /* Now estimate number of output rows, etc */ set_baserel_size_estimates(root, rel); |