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https://issues.apache.org/jira/browse/CASSANDRA-11206?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15198225#comment-15198225
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Robert Stupp commented on CASSANDRA-11206:
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Note: utests and dtests are fine now (did nothing than a rebase and re-run).
bq. partition should be added to the key cache if not already present
Yes and no. This ticket will add a _shallow_ version of {{IndexedEntry}} to the
key cache (without the IndexInfo objects as these cause a lot of heap
pressure). So, when the {{IndexInfo}} objects are actually needed, these will
be read from disk. My understanding of
{{UnfilteredRowIteratorWithLowerBound#getPartitionIndexLowerBound}} is, that it
uses the IndexInfo objects that are already in the key-cache and will go to
disk if there is a key-cache miss. If we would re-read the IndexInfo objects in
{{UnfilteredRowIteratorWithLowerBound#getPartitionIndexLowerBound}}, this would
add overhead. Or did I get it wrong and
{{UnfilteredRowIteratorWithLowerBound#getPartitionIndexLowerBound}} accesses
the same partition as {{IndexState}} does? If that's the case, we can maybe
pass the current, "fully accessible" {{IndexedEntry}} to
{{UnfilteredRowInteratorWithLowerBound}} (not checked that yet).
We could (in theory) add stuff to the partition summary or change the
serialized index - but unfortunately not in 3.x.
> Support large partitions on the 3.0 sstable format
> --------------------------------------------------
>
> Key: CASSANDRA-11206
> URL: https://issues.apache.org/jira/browse/CASSANDRA-11206
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Jonathan Ellis
> Assignee: Robert Stupp
> Fix For: 3.x
>
>
> Cassandra saves a sample of IndexInfo objects that store the offset within
> each partition of every 64KB (by default) range of rows. To find a row, we
> binary search this sample, then scan the partition of the appropriate range.
> The problem is that this scales poorly as partitions grow: on a cache miss,
> we deserialize the entire set of IndexInfo, which both creates a lot of GC
> overhead (as noted in CASSANDRA-9754) but is also non-negligible i/o activity
> (relative to reading a single 64KB row range) as partitions get truly large.
> We introduced an "offset map" in CASSANDRA-10314 that allows us to perform
> the IndexInfo bsearch while only deserializing IndexInfo that we need to
> compare against, i.e. log(N) deserializations.
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