cost_agg() with AGG_HASHED does not account for startup costs

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От David Rowley
Тема cost_agg() with AGG_HASHED does not account for startup costs
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Msg-id CAKJS1f9ygX3uFd4oHx_ZwrLTnEL1T8dqseHF2F4w9haCkhqJdQ@mail.gmail.com
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Ответы Re: cost_agg() with AGG_HASHED does not account for startup costs  (Tom Lane <tgl@sss.pgh.pa.us>)
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During working on allowing the planner to perform GROUP BY before joining I've noticed that cost_agg() completely ignores input_startup_cost when aggstrategy == AGG_HASHED.

I can see at least 3 call to cost_agg() which pass aggstrategy as AGG_HASHED that are also passing a possible non-zero startup cost.

The attached changes cost_agg() to include the startup cost, but does nothing for the changed plans in the regression tests.

Is this really intended?

Regards

David Rowley

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 David Rowley                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services
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