diff options
Diffstat (limited to 'src/backend/optimizer/path/costsize.c')
| -rw-r--r-- | src/backend/optimizer/path/costsize.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c index 88835862022..cd6dcaab190 100644 --- a/src/backend/optimizer/path/costsize.c +++ b/src/backend/optimizer/path/costsize.c @@ -663,14 +663,21 @@ cost_index(IndexPath *path, PlannerInfo *root, double loop_count, if (partial_path) { /* + * For index only scans compute workers based on number of index pages + * fetched; the number of heap pages we fetch might be so small as + * to effectively rule out parallelism, which we don't want to do. + */ + if (indexonly) + rand_heap_pages = -1; + + /* * Estimate the number of parallel workers required to scan index. Use * the number of heap pages computed considering heap fetches won't be * sequential as for parallel scans the pages are accessed in random * order. */ path->path.parallel_workers = compute_parallel_worker(baserel, - (BlockNumber) rand_heap_pages, - (BlockNumber) index_pages); + rand_heap_pages, index_pages); /* * Fall out if workers can't be assigned for parallel scan, because in |