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https://issues.apache.org/jira/browse/CASSANDRA-8931?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14646225#comment-14646225
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Jonathan Ellis commented on CASSANDRA-8931:
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Good idea. This will save a lot of memory.
> IndexSummary (and Index) should store the token, and the minimal key to
> unambiguously direct a query
> ----------------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-8931
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8931
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Benedict
> Assignee: Stefania
> Labels: performance
>
> Since these files are likely sticking around a little longer, it is probably
> worth optimising them. A relatively simple change to Index and IndexSummary
> could reduce the amount of space required significantly, reduce the CPU
> burden of lookup, and hopefully bound the amount of space needed as key size
> grows. On writing first we always store the token before the key (if it is
> different to the key); then we simply truncate the whole record to the
> minimum length necessary to answer an inequality search. Since the data file
> contains the key also, we can corroborate we have the right key once we've
> looked up. Since BFs are used to reduce unnecessary lookups, we don't save
> much by ruling the false positives out one step earlier.
> An improved follow up version would be to use a trie of shortest length to
> answer inequality lookups, as this would also ensure very long keys with
> common prefixes would not significantly increase the size of the index or
> summary. This would translate to a trie index for the summary keying into a
> static trie page for the index.
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