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https://issues.apache.org/jira/browse/CASSANDRA-6810?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13977484#comment-13977484
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Jonathan Ellis commented on CASSANDRA-6810:
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related: CASSANDRA-4324
> SSTable and Index Layout Improvements/Modifications
> ---------------------------------------------------
>
> Key: CASSANDRA-6810
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6810
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Benedict
> Labels: performance
> Fix For: 3.0
>
>
> Right now SSTables are somewhat inefficient in their storage of composite
> keys. I propose resolving this by merging (some of) the index functionality
> with the storage of keys, through introducing a composite btree/trie
> structure (e.g. string b-tree) to represent the key, and for this structure
> to index into the cell position in the file. This structure can then serve as
> both an efficient index and the key data itself.
> If we then offer the option of (possibly automatically decided for you at
> flush) storing this either packed into the same file directly prepending the
> data, or in a separate key file (with small pages), with an uncompressed page
> cache we can get good performance for wide rows by storing it separately and
> relying on the page cache for CQL row index lookups, whereas storing it
> inline will allow very efficient lookups of small rows where index lookups
> aren't particularly helpful. This removal of extra data from the index file,
> however, will allow CASSANDRA-6709 to massively scale up the efficiency of
> the key cache, whilst also reducing the total disk footprint of sstables and
> (most likely) offering better indexing capability in similar space
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