From 68119480a763d761a9cf2413f4320d9a5d4b34d5 Mon Sep 17 00:00:00 2001 From: Michael Paquier Date: Wed, 7 Jan 2026 17:52:54 +0900 Subject: [PATCH] Fix unexpected reversal of lists during catcache rehash During catcache searches, the most-recently searched entries are kept at the head of the list to speed up subsequent searches, keeping the "freshest" entries at its beginning. A rehash of the catcache was doing the opposite: fresh entries were moved to the tail of the newly-created buckets, causing a rehash to slow down a bit. When a rehash is done, this commit switches the code to use dlist_push_tail() instead of dlist_push_head(), so as fresh entries are kept at the head of the lists, not their tail. Author: ChangAo Chen Reviewed-by: John Naylor Reviewed-by: Michael Paquier Discussion: https://postgr.es/m/tencent_9EA10D8512B5FE29E7323F780A0749768708@qq.com --- src/backend/utils/cache/catcache.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/src/backend/utils/cache/catcache.c b/src/backend/utils/cache/catcache.c index 9cfda91a877..681aa923403 100644 --- a/src/backend/utils/cache/catcache.c +++ b/src/backend/utils/cache/catcache.c @@ -1013,7 +1013,14 @@ RehashCatCache(CatCache *cp) int hashIndex = HASH_INDEX(ct->hash_value, newnbuckets); dlist_delete(iter.cur); - dlist_push_head(&newbucket[hashIndex], &ct->cache_elem); + + /* + * Note that each item is pushed at the tail of the new bucket, + * not its head. This is consistent with the SearchCatCache*() + * routines, where matching entries are moved at the front of the + * list to speed subsequent searches. + */ + dlist_push_tail(&newbucket[hashIndex], &ct->cache_elem); } } @@ -1051,7 +1058,14 @@ RehashCatCacheLists(CatCache *cp) int hashIndex = HASH_INDEX(cl->hash_value, newnbuckets); dlist_delete(iter.cur); - dlist_push_head(&newbucket[hashIndex], &cl->cache_elem); + + /* + * Note that each item is pushed at the tail of the new bucket, + * not its head. This is consistent with the SearchCatCache*() + * routines, where matching entries are moved at the front of the + * list to speed subsequent searches. + */ + dlist_push_tail(&newbucket[hashIndex], &cl->cache_elem); } }