Re: How to construct an exact plan

2010/8/30 Pei He <hepeimail@gmail.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.

Regards

Pavel Stehule

>
> Thanks
> --
> Pei
>
> On Mon, Aug 30, 2010 at 1:59 PM, Josh Berkus <josh@agliodbs.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.
>>                                     http://www.pgexperts.com
>>
>
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