mirror of
https://github.com/postgres/postgres.git
synced 2026-04-14 05:27:20 -04:00
0d3dba38c7
By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. A possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only a single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. Bump WAL version number, due to a new field in xl_running_xacts. Author: Antonin Houska <ah@cybertec.at> Reviewed-by: Álvaro Herrera <alvherre@kurilemu.de> Discussion: https://postgr.es/m/90475.1775218118@localhost |
||
|---|---|---|
| .. | ||
| src | ||
| KNOWN_BUGS | ||
| Makefile | ||
| MISSING_FEATURES | ||
| TODO | ||