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https://issues.apache.org/jira/browse/CASSANDRA-15393?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16964215#comment-16964215
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Benedict Elliott Smith commented on CASSANDRA-15393:
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So first we would have to ensure we materialise to the heap anything we hold
onto with unknown lifetime (e.g. {{ColumnIndex.firstClustering}}, much like
with flushing). I don't think there are many such places.
We could then use the fact that an {{Unfiltered}} is immediately discarded
after being written, to keep in memory at most 2 {{Unfiltered}} - the one we're
maybe using, and the one that might now have been peeked at for use in the
{{MergeIterator}}.
I don't think anything more should be needed, but we'd have to look carefully.
> Add byte array backed cells
> ---------------------------
>
> Key: CASSANDRA-15393
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15393
> Project: Cassandra
> Issue Type: Sub-task
> Components: Local/Compaction
> Reporter: Blake Eggleston
> Assignee: Blake Eggleston
> Priority: Normal
> Fix For: 4.0
>
>
> We currently materialize all values as on heap byte buffers. Byte buffers
> have a fairly high overhead given how frequently they’re used, and on the
> compaction and local read path we don’t do anything that needs them. Use of
> byte buffer methods only happens on the coordinator. Using cells that are
> backed by byte arrays instead in these situations reduces compaction and read
> garbage up to 22% in many cases.
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