pgsql: Fix unexpected reversal of lists during catcache rehash

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 <cca5507(at)qq(dot)com>
Reviewed-by: John Naylor <johncnaylorls(at)gmail(dot)com>
Reviewed-by: Michael Paquier <michael(at)paquier(dot)xyz>
Discussion: https://postgr.es/m/tencent_9EA10D8512B5FE29E7323F780A0749768708@qq.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/68119480a763d761a9cf2413f4320d9a5d4b34d5

Modified Files
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src/backend/utils/cache/catcache.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)