Dear hackers, Hi, this is a fork thread from [1]. I want to propose a small optimization for logical replication system.
Background ========== When the ALTER PUBLICATION command is executed, all entries in RelationSyncCache will be discarded anyway. This mechanism works well but is sometimes not efficient. For example, when the ALTER PUBLICATION DROP TABLE is executed, 1) the specific entry in RelationSyncCache will be removed, and then 2) all entries will be discarded twice. This happens because the pgoutput plugin registers both RelcacheCallback (rel_sync_cache_relation_cb) and SyscacheCallback (publication_invalidation_cb, rel_sync_cache_publication_cb). Then, when ALTER PUBLICATION ADD/SET/DROP is executed, both the relation cache of added tables and the syscache of pg_publication_rel and pg_publication are invalidated. The callback for the relation cache will remove an entry from the hash table, and syscache callbacks will look up all entries and invalidate them. However, AFAICS does not need to invalidate all of them. I grepped source codes and found this happens since the initial version. Currently the effect of the behavior may not be large, but [1] may affect significantly because it propagates invalidation messages to all in-progress decoding transactions. Patch overview ============ Based on the background, the patch avoids dropping all entries in RelationSyncCache when ALTER PUBLICATION is executed. It removes sys cache callbacks for pg_publication_rel and pg_publication_namespace and avoids discarding entries in sys cache for pg_publication. Apart from the above, this patch also ensures that relcaches of publishing tables are invalidated when ALTER PUBLICATION is executed. ADD/SET/DROP already has this mechanism, but ALTER PUBLICATION OWNER TO and RENAME TO do not. Regarding RENAME TO, now we are using a common function, but it is replaced with RenamePublication() to do invalidations. How do you think? [1]: https://www.postgresql.org/message-id/de52b282-1166-1180-45a2-8d8917ca7...@enterprisedb.com Best regards, Hayato Kuroda FUJITSU LIMITED
0001-Selectively-invalidate-cache-in-pgoutput.patch
Description: 0001-Selectively-invalidate-cache-in-pgoutput.patch
