More details for 'tail prefetch size is calculated based on'

facebook / rocksdb

A library that provides an embeddable, persistent key-value store for fast storage.

http://rocksdb.org

GNU General Public License v2.0

28.09k stars 6.25k forks source link

More details for 'tail prefetch size is calculated based on' #12667

Closed andlr closed 2 months ago

andlr commented 3 months ago

These messages indicate that SST file was created by a pre-9.0.0 RocksDB. Eventually, TailPrefetchStats might be removed, so it would be more informative if log message also included name of the affected SST file.

Issue: #12664

facebook-github-bot commented 3 months ago

@hx235 has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

facebook-github-bot commented 3 months ago

@andlr has updated the pull request. You must reimport the pull request before landing.

andlr commented 3 months ago

It is a warning so we can track use cases that are at risk of regression when we finally remove TailPrefetchStats. The warnings and the risk can be mitigated by running compaction with a new enough RocksDB version (see #12664). If you still wanted to make a code change here, may I suggest a couple ideas:

As you mentioned the documentation was inadequate to know what to do. Maybe the warning text or surrounding comments could be improved.

Deduplicating the error could help with the spam problem. Maybe one warning per DB open saying N files are at risk.

Thanks for the explanation. I think in such case, it's probably enough to add name of the SST file into the log message, and a comment in code, saying that this backward compatibility won't be preserved forever

facebook-github-bot commented 3 months ago

@hx235 has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.