diff options
| -rw-r--r-- | src/backend/optimizer/path/costsize.c | 7 |
1 files changed, 3 insertions, 4 deletions
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c index acd859bede..d9789c2a0e 100644 --- a/src/backend/optimizer/path/costsize.c +++ b/src/backend/optimizer/path/costsize.c @@ -2558,11 +2558,10 @@ cost_memoize_rescan(PlannerInfo *root, MemoizePath *mpath, * must look at how many scans are estimated in total for this node and * how many of those scans we expect to get a cache hit. */ - hit_ratio = 1.0 / ndistinct * Min(est_cache_entries, ndistinct) - - (ndistinct / calls); + hit_ratio = ((calls - ndistinct) / calls) * + (est_cache_entries / Max(ndistinct, est_cache_entries)); - /* Ensure we don't go negative */ - hit_ratio = Max(hit_ratio, 0.0); + Assert(hit_ratio >= 0 && hit_ratio <= 1.0); /* * Set the total_cost accounting for the expected cache hit ratio. We |