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https://issues.apache.org/jira/browse/DERBY-4818?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12914464#action_12914464
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Rick Hillegas commented on DERBY-4818:
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Hi Trung,
You may be interested in reading this high level description of the Derby
optimizer: http://db.apache.org/derby/papers/optimizer.html The Derby optimizer
considers left-deep join trees. That means that for a query with N tables, the
time spent optimizing the query is roughly proportional to N! . As the number
of tables grows, the number of possible plans mushrooms.
Hope this is useful,
-Rick
> Derby is taking a long time to parse SQLs with more than 9 tables for the
> first time.
> -------------------------------------------------------------------------------------
>
> Key: DERBY-4818
> URL: https://issues.apache.org/jira/browse/DERBY-4818
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.4.1.3
> Environment: All OS platforms and all JVM versions on Derby 10.4.1.3
> Reporter: Trung Tran
>
> I have SQLs with 9 or more tables and it takes a couple of minutes to compile
> these SQLs for the first time. I'm assuming that the optimizer is taking a
> long time to figure out the query plan.
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