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Fix unexpected reversal of lists during catcache rehash

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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 <cca5507@qq.com>
Reviewed-by: John Naylor <johncnaylorls@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/tencent_9EA10D8512B5FE29E7323F780A0749768708@qq.com
This commit is contained in:
Michael Paquier
2026-01-07 17:52:54 +09:00
parent ba887a8cdb
commit 68119480a7
1 changed files with 16 additions and 2 deletions
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18
src/backend/utils/cache/catcache.c vendored
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@@ -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);
}
}