Disable updating fs cache during backup/restore.

[vitlibar]

Changelog category:

• Improvement

Changelog entry:

Disable updating fs cache during backup/restore. Filesystem cache must not be updated during backup/restore, it seems it just slows down the process without any profit (because the BACKUP command can read a lot of data and it's no use to put all the data to the filesystem cache and immediately evict it).

[robot-ch-test-poll]

This is an automated comment for commit 587877d with description of existing statuses. It's updated for the latest CI running
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The overall status of the commit is 🟡 pending

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[kssenii]

setting read_from_filesystem_cache_if_exists_otherwise_bypass_cache will not work if enable_filesystem_cache is disabled, see

ClickHouse/src/Disks/IO/ReadBufferFromRemoteFSGather.cpp

Lines 21 to 23 in 5ea0971

	return settings.remote_fs_cache && settings.enable_filesystem_cache
	&& (!CurrentThread::getQueryId().empty() || settings.read_from_filesystem_cache_if_exists_otherwise_bypass_cache
	|| !settings.avoid_readthrough_cache_outside_query_context);

may be better something like this?

read_settings.enable_filesystem_cache = backup_settings.read_from_filesystem_cache_if_exists_otherwise_bypass_cache;
read_settings.read_from_filesystem_cache_if_exists_otherwise_bypass_cache = backup_settings.read_from_filesystem_cache_if_exists_otherwise_bypass_cache;
read_settings.avoid_readthrough_cache_outside_query_context = false; /// not sure if needed

[vitlibar]

Thank you!

avoid_readthrough_cache_outside_query_context doesn't seem necessary because though BACKUP/RESTORE can operate in background they always have proper query id. Anyway the tests pass.

[kssenii]

also may be add a test?

[vitlibar]

also may be add a test?

I added test.

[vitlibar]

Integration tests (tsan) [6/6] - #52554