On Sat, Aug 12, 2023 at 08:15:31PM -0700, Noah Misch wrote: > The attached 010_zero.pl, when run as part of the pg_waldump test suite, fails > at today's master (c36b636) and v15 (1bc19df). It passes at v14 (5a32af3). > Command "pg_waldump --start 0/01000000 --end 0/01000100" fails as follows: > > pg_waldump: error: WAL segment size must be a power of two between > 1 MB and 1 GB, but the WAL file "000000010000000000000002" header > specifies 0 bytes
So this depends on the ordering of the entries retrieved by readdir() as much as the segments produced by the backend. > Where it fails, the server has created an all-zeros WAL file under that name. > Where it succeeds, that file doesn't exist at all. Two decisions to make: > > - Should a clean server shutdown ever leave an all-zeros WAL file? I think > yes, it's okay to let that happen. It doesn't hurt to leave that around. On the contrary, it makes any follow-up startup cheaper the bigger the segment size. > - Should "pg_waldump --start $X --end $Y" open files not needed for the > requested range? I think no. So this is a case where identify_target_directory() is called with a fname of NULL. Agreed that search_directory could be smarter with the files it should scan, especially if we have start and/or end LSNs at hand to filter out what we'd like to be in the data folder. -- Michael
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