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https://issues.apache.org/jira/browse/CASSANDRA-11206?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15328785#comment-15328785
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Michael Kjellman commented on CASSANDRA-11206:
----------------------------------------------
going thru the changes and have some questions :)
# RowIndexEntry$serializedSize used to return the size of the index for the
entire row. As the size of the IndexInfo elements are variable length I'm
having trouble understanding how the new/current implementation does this:
{code}
private static int serializedSize(DeletionTime deletionTime, long headerLength,
int columnIndexCount)
{
return TypeSizes.sizeofUnsignedVInt(headerLength)
+ (int) DeletionTime.serializer.serializedSize(deletionTime)
+ TypeSizes.sizeofUnsignedVInt(columnIndexCount);
}
{code}
# In the class level Javadoc for IndexInfo there is a lot of comment about
serialization format changes and even a comment "Serialization format changed
in 3.0" yet I don't see any corresponding changes in BigFormat$BigVersion
> 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
> Components: Local Write-Read Paths
> Reporter: Jonathan Ellis
> Assignee: Robert Stupp
> Labels: docs-impacting
> Fix For: 3.6
>
> Attachments: 11206-gc.png, trunk-gc.png
>
>
> 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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