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Diffstat (limited to 'src/backend/optimizer/path')
| -rw-r--r-- | src/backend/optimizer/path/allpaths.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c index 5db1688bf04..5f74d3b36d9 100644 --- a/src/backend/optimizer/path/allpaths.c +++ b/src/backend/optimizer/path/allpaths.c @@ -620,7 +620,20 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel, * the SubqueryScanPath as not parallel-safe. (Note that * set_subquery_pathlist() might push some of these quals down * into the subquery itself, but that doesn't change anything.) + * + * We can't push sub-select containing LIMIT/OFFSET to workers as + * there is no guarantee that the row order will be fully + * deterministic, and applying LIMIT/OFFSET will lead to + * inconsistent results at the top-level. (In some cases, where + * the result is ordered, we could relax this restriction. But it + * doesn't currently seem worth expending extra effort to do so.) */ + { + Query *subquery = castNode(Query, rte->subquery); + + if (limit_needed(subquery)) + return; + } break; case RTE_JOIN: |