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Re: How to construct an exact plan

From: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
To: Pei He <hepeimail(at)gmail(dot)com>
Cc: Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: How to construct an exact plan
Date: 2010-08-30 19:41:50
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Lists: pgsql-hackers
2010/8/30 Pei He <hepeimail(at)gmail(dot)com>:
> Hi,
> I am hacking postgresql 8.2.5. a) and b) do not work for me.
> The situation is that I made a join operator, and a scan operator.
> And, The join operator requires the scan operator as the inner. So, I
> need to have the full control of the join plan.
> I am not ready to provide the optimization support for the two new
> operators. And, I want to run some performance tests before working on
> the optimization part.
> So, I want to know if it is possible to directly create a path or a
> plan, and do a unit test for the operators.

yes, it is possible - but it isn't simple. I thing, so better is
simple implementation of all parts and then runtime blocking some (for
you not interesting) buildin methods via SET enable_.... to off.


Pavel Stehule

> Thanks
> --
> Pei
> On Mon, Aug 30, 2010 at 1:59 PM, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
>>> I have developed a new operators, and I want to do some tests on it.
>>> I do not want the optimizer to choose the plan for me, and I need to
>>> construct a plan as exact as I want.
>>> Can anyone provide me a way to achieve that?
>> a) easy: choose a simple enough query that its plan is always predictable.
>> b) moderate: choose a query whose plan is predictable if you manipulate
>> the enable_* configuration settings
>> c) hard: hack the PostgreSQL planner to choose a specific execution
>> plan, and recompile Postgres.
>> --
>>                                  -- Josh Berkus
>>                                     PostgreSQL Experts Inc.
> --
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