Allow WAL summarization to back up when timeline changes.
The old code believed that it was not possible to switch timelines
without first replaying all of the WAL from the old timeline, but
that turns out to be false, as demonstrated by an example from Fujii
Masao. As a result, it assumed that summarization would always
continue from the LSN where summarization previously ended. But in
fact, when a timeline switch occurs without replaying all the WAL
from the previous timeline, we can need to back up to an earlier
LSN. Adjust accordingly.
Discussion: https://postgr.es/m/CA+TgmoZGEsZodXC4f=XZNkAeyuDmWTSkpkjCEOcF19Am0mt_OA@mail.gmail.com
Branch
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REL_17_STABLE
Details
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https://git.postgresql.org/pg/commitdiff/c7cfbc5157fec24704ea102f113d97193ffe5f7f
Modified Files
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src/backend/postmaster/walsummarizer.c | 32 +++++++++++++++++++-------------
1 file changed, 19 insertions(+), 13 deletions(-)