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From "Benedict (JIRA)" <>
Subject [jira] [Resolved] (CASSANDRA-6810) SSTable and Index Layout Improvements/Modifications
Date Mon, 30 Jun 2014 16:02:24 GMT


Benedict resolved CASSANDRA-6810.

    Resolution: Duplicate

> SSTable and Index Layout Improvements/Modifications
> ---------------------------------------------------
>                 Key: CASSANDRA-6810
>                 URL:
>             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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