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Posted to issues@quickstep.apache.org by "Harshad Deshmukh (JIRA)" <ji...@apache.org> on 2017/03/23 15:46:41 UTC

[jira] [Created] (QUICKSTEP-85) Don't use hash table load factor when exact estimate is known

Harshad Deshmukh created QUICKSTEP-85:
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             Summary: Don't use hash table load factor when exact estimate is known
                 Key: QUICKSTEP-85
                 URL: https://issues.apache.org/jira/browse/QUICKSTEP-85
             Project: Apache Quickstep
          Issue Type: Improvement
          Components: Storage
            Reporter: Harshad Deshmukh
            Assignee: Harshad Deshmukh


By default the join hash tables use a load factor of 0.5, which means we allocate double the amount of estimated space required by the hash table. In cases when the estimate is accurate (either the stats are perfect or the hash table is being built on a stored table) we should not use this load factor, thereby saving space.



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