pgsql: Allow old WAL recycling during REPACK CONCURRENTLY

Allow old WAL recycling during REPACK CONCURRENTLY

During REPACK CONCURRENTLY, logical decoding keeps replication
slot.restart_lsn pinned behind the oldest running transaction, which is
often the long-lived REPACK transaction itself. As a result, old WAL
segments are retained longer than necessary.

This commit advances the replication slot each time WAL insertion
crosses a segment boundary, so obsolete WAL files can be recycled while
REPACK is still running.

Author: Zhijie Hou <houzj(dot)fnst(at)fujitsu(dot)com>
Reviewed-by: Antonin Houska <ah(at)cybertec(dot)at>
Reviewed-by: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>

Discussion: https://postgr.es/m/TY4PR01MB17718B44164522D0798F8E898940A2@TY4PR01MB17718.jpnprd01.prod.outlook.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/45b02984e2fa9ee7bd83f7e58797b160baf0cc13

Modified Files
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src/backend/commands/repack_worker.c | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)