diff options
| author | Tom Lane | 2022-07-28 18:34:32 +0000 |
|---|---|---|
| committer | Tom Lane | 2022-07-28 18:34:32 +0000 |
| commit | e09d7a1262c659578065eaf7edafe606d2c8ebf2 (patch) | |
| tree | a20bedfb3536af659716e32d756a9103954ab732 /src/backend/access | |
| parent | 70a437aa45b6dcacc2ad894f95ef5bb46b26035f (diff) | |
Improve speed of hash index build.
In the initial data sort, if the bucket numbers are the same then
next sort on the hash value. Because index pages are kept in
hash value order, this gains a little speed by allowing the
eventual tuple insertions to be done sequentially, avoiding repeated
data movement within PageAddItem. This seems to be good for overall
speedup of 5%-9%, depending on the incoming data.
Simon Riggs, reviewed by Amit Kapila
Discussion: https://postgr.es/m/CANbhV-FG-1ZNMBuwhUF7AxxJz3u5137dYL-o6hchK1V_dMw86g@mail.gmail.com
Diffstat (limited to 'src/backend/access')
| -rw-r--r-- | src/backend/access/hash/hashsort.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/src/backend/access/hash/hashsort.c b/src/backend/access/hash/hashsort.c index aa61e39f26a..19563148d05 100644 --- a/src/backend/access/hash/hashsort.c +++ b/src/backend/access/hash/hashsort.c @@ -42,9 +42,10 @@ struct HSpool Relation index; /* - * We sort the hash keys based on the buckets they belong to. Below masks - * are used in _hash_hashkey2bucket to determine the bucket of given hash - * key. + * We sort the hash keys based on the buckets they belong to, then by the + * hash values themselves, to optimize insertions onto hash pages. The + * masks below are used in _hash_hashkey2bucket to determine the bucket of + * a given hash key. */ uint32 high_mask; uint32 low_mask; |