On 30/04/2013 5:20 PM, Nico Williams wrote:
On Tue, Apr 30, 2013 at 11:59 AM, Richard Hipp <[email protected]> wrote:
http://www.sqlite.org/draft/queryplanner-ng.html
That's quite interesting.
Should the user have a way to influence the query planner? Perhaps by
indicating a cost for each table source? SQL is supposed to let the
RDBMS pick the best query plan, but the RDBMS can't always pick the
best plan... in such cases users like to have a way to dictate the
plan. And/or the RDBMS could keep state about different plans tried
in the past and learn to pick better plans, but this sounds very
complicated.
My experience with cross joins and TPCH Q8 suggests that in cases like
this the user's not necessarily going to pick a good join ordering,
either. At least I had bad luck with it. Being able to force certain
access methods (use *this* index, not that one) would be helpful, though
(does "+" do that or just suggest it?).
Ryan
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