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https://issues.apache.org/jira/browse/DERBY-7173?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17913038#comment-17913038
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Richard Evans commented on DERBY-7173:
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Additionally, with 2 query clauses, and accumulating the time taken:
# in prepareStatement
# in executeQuery
# looping over the result set
The first two average out at around 0.02ms whilst the third averages out at
around 7.6ms.
With a single query clause, all three average out at about 0.02ms.
Seems that with two query clauses, almost all of the time is taken retrieving
the results.
> Very poor performance with a = ? AND b = ? OR a = ? AND b = ? in query
> ----------------------------------------------------------------------
>
> Key: DERBY-7173
> URL: https://issues.apache.org/jira/browse/DERBY-7173
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.16.1.1
> Reporter: Richard Evans
> Priority: Major
> Attachments: lkp.java
>
>
> Execute a query like:
> SELECT * FROM table WHERE col1 = ? AND col2 = ? OR col1 = ? AND col2 = ?
> Performance is significantly worse then the simpler:
> SELECT * FROM table WHERE col1 = ? AND col2 = ?
> even though both col1 and col2 are indexed.
> Simple test case attached - run with db directory and number of OR clauses in
> query - use 2 for first example above and 1 for second.
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