Revert "Add redo LSN to pgstats files" This reverts commit b860848232aa, that was added as a prerequisite for the support of pgstats data flush across checkpoints, linking a pgstats file to a specific checkpoint redo LSN.
As reported, this is proving to be currently problematic when going through a pg_upgrade, that does direct manipulations of the control file in the new cluster. The LSN stored in the pgstats file is not able to cope with any changes done in the control file by pg_upgrade yet, causing the pgstats file to be discarded when starting the new cluster after overriding its redo LSN (one is a `pg_resetwal -l` where the new cluster's start LSN is bumped by a hardcoded value of 8 segments, see copy_xact_xlog_xid). The least painful path going forward is likely going to be a refactor of the pgstats code so as it is possible to read and write some of its data with some routines in src/common/, so as pg_upgrade or pg_resetwal are able to update its data. The main point is that we are going to need a LSN in the stats file should we make it written at checkpoint time and not only as part of a shutdown sequence. It is too late to dive into these details for v18, so let's revert the change, and let's try to figure out all the details in the next release cycle. The pgstats file is currently only written as part of a shutdown sequence, and its contents are still lost on crash, same as older releases. Bump PGSTAT_FILE_FORMAT_ID. Reported-by: Tom Lane <t...@sss.pgh.pa.us> Discussion: https://postgr.es/m/2563883.1741826...@sss.pgh.pa.us Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/5721e5453ebc59360b6756fe72d7499c4a02177c Modified Files -------------- src/backend/access/transam/xlog.c | 2 +- src/backend/utils/activity/pgstat.c | 41 ++++++++----------------------------- src/include/pgstat.h | 5 ++--- 3 files changed, 12 insertions(+), 36 deletions(-)
