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https://issues.apache.org/jira/browse/CASSANDRA-10520?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15885764#comment-15885764
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Branimir Lambov commented on CASSANDRA-10520:
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I'm not very comfortable with using different defaults for existing vs new
tables -- a choice like this looks fragile and can lead to confusion.
Nevertheless, my personal preference is to not introduce unnecessary risk, and
my vote would be to keep the option off by default (for both existing and new
tables).
> Compressed writer and reader should support non-compressed data.
> ----------------------------------------------------------------
>
> Key: CASSANDRA-10520
> URL: https://issues.apache.org/jira/browse/CASSANDRA-10520
> Project: Cassandra
> Issue Type: Improvement
> Components: Local Write-Read Paths
> Reporter: Branimir Lambov
> Assignee: Branimir Lambov
> Labels: messaging-service-bump-required
> Fix For: 4.x
>
> Attachments: ReadWriteTestCompression.java
>
>
> Compressing uncompressible data, as done, for instance, to write SSTables
> during stress-tests, results in chunks larger than 64k which are a problem
> for the buffer pooling mechanisms employed by the
> {{CompressedRandomAccessReader}}. This results in non-negligible performance
> issues due to excessive memory allocation.
> To solve this problem and avoid decompression delays in the cases where it
> does not provide benefits, I think we should allow compressed files to store
> uncompressed chunks as alternative to compressed data. Such a chunk could be
> written after compression returns a buffer larger than, for example, 90% of
> the input, and would not result in additional delays in writing. On reads it
> could be recognized by size (using a single global threshold constant in the
> compression metadata) and data could be directly transferred into the
> decompressed buffer, skipping the decompression step and ensuring a 64k
> buffer for compressed data always suffices.
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