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From "Mamta A. Satoor (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-573) Provider support for optimizer overrides in Derby.
Date Tue, 20 Sep 2005 05:54:28 GMT
    [ http://issues.apache.org/jira/browse/DERBY-573?page=comments#action_12329952 ] 

Mamta A. Satoor commented on DERBY-573:

There was discussion about various possible options to support optimizer hints in the past.
One thread on this is titled "Optimizer hints?" at http://mail-archives.apache.org/mod_mbox/db-derby-dev/200412.mbox/%3c41C360A6.3050400@Sourcery.Org%3e.
The other thread is titled "Join order and access path" at http://mail-archives.apache.org/mod_mbox/db-derby-dev/200502.mbox/%3cBAY3-F62B405CA29E874AB32DA5CF6F0@phx.gbl%3e.
In the absence of SQL standard way of implementing this and based on the 2 email threads,
I proposed to implement this with special comments --PROPERTIES.

Also, since the time I wrote the functional spec, I have been tweaking the parser to ignore
white spaces(this includes " ", "\t") between -- and PROPERTIES to make parser more flexible
about how a user specifies the properties. My work in the parser to support the optimizer
hints is not completely finished. Hope to make more progress in couple days.

> Provider support for optimizer overrides in Derby.
> --------------------------------------------------
>          Key: DERBY-573
>          URL: http://issues.apache.org/jira/browse/DERBY-573
>      Project: Derby
>         Type: New Feature
>   Components: SQL
>     Versions:
>     Reporter: Mamta A. Satoor
>     Assignee: Mamta A. Satoor
>  Attachments: optimizeroverrides.html
> Derby's query optimizer usually makes the best choice of join order and access path.
The default join strategy ususally works the best too. However, there are some cases in which
user may want to override the optimizer or the default values. Providing support for optimizer
overrides will allow users to hand-tune the optimizer for queries. 

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