From: | David Rowley <dgrowleyml(at)gmail(dot)com> |
---|---|
To: | Amit Langote <amitlangote09(at)gmail(dot)com> |
Cc: | Andy Fan <zhihui(dot)fan1213(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: Wired if-statement in gen_partprune_steps_internal |
Date: | 2021-04-08 10:40:46 |
Message-ID: | CAApHDvrWOBRzX=D+328=i8ZVOzzHd-O85to1E8e9wgVTuz43Vg@mail.gmail.com |
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On Thu, 8 Apr 2021 at 21:04, Amit Langote <amitlangote09(at)gmail(dot)com> wrote:
> + * These partition pruning steps come in 2 forms; operation steps and combine
> + * steps.
>
> Maybe you meant "operator" steps? IIRC, the reason why we named it
> PartitionPruneStepOp is that an op step is built to prune based on the
> semantics of the operators that were involved in the matched clause.
> Although, they're abused for pruning based on nullness clauses too.
> Maybe, we should also updated the description of node struct as
> follows to consider that last point:
Oh right. Thanks. I fixed that.
> * PartitionPruneStepOp - Information to prune using a set of mutually ANDed
> * OpExpr and any IS [ NOT ] NULL clauses
>
> + * Combine steps (PartitionPruneStepCombine) instruct the partition pruning
> + * code how it should produce a single set of partitions from multiple input
> + * operation steps.
I didn't add that. I wasn't really sure if I understood why we'd talk
about PartitionPruneStepCombine in the PartitionPruneStepOp. I thought
the overview in gen_partprune_steps_internal was ok to link the two
together and explain why they're both needed.
> I think the last part should be: ...from multiple operation/operator
> and [ other ] combine steps.
Change that and pushed.
David
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