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| author | Alexander Korotkov | 2025-05-18 20:49:50 +0000 |
|---|---|---|
| committer | Alexander Korotkov | 2025-05-18 20:49:50 +0000 |
| commit | 3d3a81fc24b07f04df81d898f6b4e85c553ef604 (patch) | |
| tree | 80df4269d9ed7c2655ca8fa2953ac2147500ba49 /src/backend/optimizer | |
| parent | 12eee85e511ff8854ac61e8caad8cec218b20513 (diff) | |
Fix tuple_fraction calculation in generate_orderedappend_paths()
6b94e7a6da adjusted generate_orderedappend_paths() to consider fractional
paths. However, it didn't manage to interpret the tuple_fraction value
correctly. According to the header comment of grouping_planner(), the
tuple_fraction >= 1 specifies the absolute number of expected tuples. That
number must be divided by the expected total number of tuples to get the
actual fraction.
Even though this is a bug fix, we don't backpatch it. The risks of the side
effects of plan changes on stable branches are too high.
Reported-by: Andrei Lepikhov <[email protected]>
Discussion: https://postgr.es/m/3ca271fa-ca5c-458c-8934-eb148622b270%40gmail.com
Author: Andrei Lepikhov <[email protected]>
Reviewed-by: Junwang Zhao <[email protected]>
Reviewed-by: Alvaro Herrera <[email protected]>
Reviewed-by: Tom Lane <[email protected]>
Diffstat (limited to 'src/backend/optimizer')
| -rw-r--r-- | src/backend/optimizer/path/allpaths.c | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c index 905250b3325..6cc6966b060 100644 --- a/src/backend/optimizer/path/allpaths.c +++ b/src/backend/optimizer/path/allpaths.c @@ -1891,7 +1891,17 @@ generate_orderedappend_paths(PlannerInfo *root, RelOptInfo *rel, */ if (root->tuple_fraction > 0) { - double path_fraction = (1.0 / root->tuple_fraction); + double path_fraction = root->tuple_fraction; + + /* + * Merge Append considers only live children relations. Dummy + * relations must be filtered out before. + */ + Assert(childrel->rows > 0); + + /* Convert absolute limit to a path fraction */ + if (path_fraction >= 1.0) + path_fraction /= childrel->rows; cheapest_fractional = get_cheapest_fractional_path_for_pathkeys(childrel->pathlist, |