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https://issues.apache.org/jira/browse/CASSANDRA-299?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12742015#action_12742015
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Jonathan Ellis commented on CASSANDRA-299:
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what i'm saying is, you should still open() all tables (i don't see the benefit
in changing that, and it would cause some pain i think), but the scanning for
data files should not be per-table but at a higher level to avoid O(N) system
calls scanning datafiledirectories, when it really only needs to be O(1). (of
course the subdirs then need to be scanned per-table).
this involves breaking the current encapsulation but it will make a big
difference if we want to support 10000s of Tables. (and i think we do.)
> make table directory creation lazy
> ----------------------------------
>
> Key: CASSANDRA-299
> URL: https://issues.apache.org/jira/browse/CASSANDRA-299
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Jonathan Ellis
> Priority: Minor
> Fix For: 0.5
>
>
> checking that each subdir for each table is present on startup -- _every_
> startup -- could be a real pita.
> i think that to support 100k tables (not impossible, in a
> hosted-cassandra-as-a-service scenario) we're going to want to make table dir
> creation lazy.
> then we would want to make scanning for sstables faster by only doing one
> listdir call per datadir, to see which table subdirs are present, and then
> checking only those for sstable files. this would involve some re-org of the
> onstart code.
> (note that we don't want to prune directories if there are no sstables left
> in them, since we'd end up re-creating them at some point anyway; we just
> want to allow the lack of a table subdir to imply the same thing as an empty
> one.)
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