Benedict created CASSANDRA-8931:
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Summary: 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
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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