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https://issues.apache.org/jira/browse/DERBY-890?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Mamta A. Satoor updated DERBY-890:
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Urgency: Normal
Labels: derby_triage10_11 (was: )
> Improve query processing of Derby by evaluating common sub expressions only
> once, rather than evaluating them many times.
> -------------------------------------------------------------------------------------------------------------------------
>
> Key: DERBY-890
> URL: https://issues.apache.org/jira/browse/DERBY-890
> Project: Derby
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 10.1.3.1, 10.2.1.6
> Environment: generic
> Reporter: Satheesh Bandaram
> Labels: derby_triage10_11
>
> Improve Derby query processing by evaluating common sub-expressions only
> once. There have been discussions about common expression evaluations in
> DerbyDev list in the past that can be searched on for details.
> Here is one example query that could benifit by this optimization. Reported
> by Harri Pesonen.
> Select min(i) from BIG_TABLE is fast (with index on i) where as Select
> min(i), min(i)+1 from BIG_TABLE is slooow.
> There are potentially many possible queries that could benifit by this
> optimization.
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