From e4b0a02ef8c8c69f2a49f4ca86de12ef34e97ac3 Mon Sep 17 00:00:00 2001 From: Noah Misch Date: Sat, 21 Mar 2020 09:38:26 -0700 Subject: Skip WAL for new relfilenodes, under wal_level=minimal. Until now, only selected bulk operations (e.g. COPY) did this. If a given relfilenode received both a WAL-skipping COPY and a WAL-logged operation (e.g. INSERT), recovery could lose tuples from the COPY. See src/backend/access/transam/README section "Skipping WAL for New RelFileNode" for the new coding rules. Maintainers of table access methods should examine that section. To maintain data durability, just before commit, we choose between an fsync of the relfilenode and copying its contents to WAL. A new GUC, wal_skip_threshold, guides that choice. If this change slows a workload that creates small, permanent relfilenodes under wal_level=minimal, try adjusting wal_skip_threshold. Users setting a timeout on COMMIT may need to adjust that timeout, and log_min_duration_statement analysis will reflect time consumption moving to COMMIT from commands like COPY. Internally, this requires a reliable determination of whether RollbackAndReleaseCurrentSubTransaction() would unlink a relation's current relfilenode. Introduce rd_firstRelfilenodeSubid. Amend the specification of rd_createSubid such that the field is zero when a new rel has an old rd_node. Make relcache.c retain entries for certain dropped relations until end of transaction. Back-patch to 9.5 (all supported versions). This introduces a new WAL record type, XLOG_GIST_ASSIGN_LSN, without bumping XLOG_PAGE_MAGIC. As always, update standby systems before master systems. This changes sizeof(RelationData) and sizeof(IndexStmt), breaking binary compatibility for affected extensions. (The most recent commit to affect the same class of extensions was 089e4d405d0f3b94c74a2c6a54357a84a681754b.) Kyotaro Horiguchi, reviewed (in earlier, similar versions) by Robert Haas. Heikki Linnakangas and Michael Paquier implemented earlier designs that materially clarified the problem. Reviewed, in earlier designs, by Andrew Dunstan, Andres Freund, Alvaro Herrera, Tom Lane, Fujii Masao, and Simon Riggs. Reported by Martijn van Oosterhout. Discussion: https://postgr.es/m/20150702220524.GA9392@svana.org --- src/include/access/gistxlog.h | 1 + 1 file changed, 1 insertion(+) (limited to 'src/include/access/gistxlog.h') diff --git a/src/include/access/gistxlog.h b/src/include/access/gistxlog.h index e44922d915c..596a881e49f 100644 --- a/src/include/access/gistxlog.h +++ b/src/include/access/gistxlog.h @@ -26,6 +26,7 @@ /* #define XLOG_GIST_INSERT_COMPLETE 0x40 */ /* not used anymore */ /* #define XLOG_GIST_CREATE_INDEX 0x50 */ /* not used anymore */ #define XLOG_GIST_PAGE_DELETE 0x60 +#define XLOG_GIST_ASSIGN_LSN 0x70 /* nop, assign new LSN */ /* * Backup Blk 0: updated page. -- cgit v1.2.3