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https://issues.apache.org/jira/browse/CASSANDRA-9225?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14510636#comment-14510636
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Sylvain Lebresne commented on CASSANDRA-9225:
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bq. We want to split sstables based on their compressed size
Of course, I wasn't thinking clearly. Patch fixes the test with compression, +1.
> CompactionAwareWriterTest is broken with compression
> ----------------------------------------------------
>
> Key: CASSANDRA-9225
> URL: https://issues.apache.org/jira/browse/CASSANDRA-9225
> Project: Cassandra
> Issue Type: Bug
> Reporter: Sylvain Lebresne
> Assignee: Marcus Eriksson
> Priority: Trivial
> Fix For: 3.0
>
> Attachments: 0001-9225.patch
>
>
> {{CompactionAwareWriterTest}} generates a relatively small sstable and expect
> different types of compaction to split it at relatively precise sizes.
> However, the implementations of {{CompactionAwareWriter}} use
> {{writer.getOnDiskFilePointer()}} to decide when to split and with
> compression that value is updated only when an compressed block is written.
> Which means that with compression the splitting is not as precise as the test
> expects it to be and the test fails.
> Note that this imprecision in splitting is not a big deal in practice (you
> might even call it a feature) since you expect to split sstables at sizes
> that are a lot bigger than the compression block size (besides, we already
> know we are imprecise in our splitting size since we only split at partition
> boundaries). But this does make things a bit harder to test.
> So I guess we could either:
> # make the test use much bigger values so it's not affected by the
> imprecision (with the small downside that it will make the test slower)
> # remove that imprecision by making the {{CompactionAwareWriter}}
> implementations use {{writer.getFilePointer()}}.
> I don't have much personal preference but using {{getFilePointer}} sounds
> like the simpler fix, and it feels overall more predictable.
> Note that the test is not failing on trunk because unit tests do not use
> compression, you have to call {{ant test-compression}} for that (in which
> case it will fail). We might want to make compression one our randomized
> parameter of tests in the near future as I'm not sure anyone is really
> running {{ant test-compression}} on a regular basis.
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