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From Knut Anders Hatlen <knut.hat...@oracle.com>
Subject Re: How Much Memory for hash joins
Date Thu, 28 Feb 2013 17:34:13 GMT
Mike Matrigali <mikem_app@sbcglobal.net> writes:

> I have always assumed that the intent of the option is per opened
> "table" in store.  This is not user friendly at all since user does
> not really know how this matches up to their query, which is likely
> why the option was never made public for a zero admin db.

There's a brief discussion in DERBY-4620 on how this setting could be
auto-tuned.

Also, the memory estimates we use for the hash tables are inaccurate
(they are too low), so maxMemoryPerTable is effectively higher than its
nominal value. There's a patch attached to the issue that fixes the
estimates, but I've been hesitant to check it in, since it changes a lot
of query plans in the regression tests (wisconsin & co).

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