Re: numbering plan nodes

On Thu, Sep 17, 2015 at 9:01 PM, Kouhei Kaigai <kaigai@ak.jp.nec.com> wrote:
> I entirely agree with the idea of plan-node identifier, however,
> uncertain whether the node-id shall represent physical location on
> the dynamic shared memory segment, because
> (1) Relatively smaller number of node type needs shared state,
>     thus most of array items are empty.
> (2) Extension that tries to modify plan-tree using planner_hook
>     may need to adjust node-id also.
>
> Even though shm_toc_lookup() has to walk on the toc entries to find
> out the node-id, it happens at once on beginning of the executor at
> background worker side. I don't think it makes a significant problem.

Yes, I was thinking that what would make sense is to have each
parallel-aware node call shm_toc_insert() using its ID as the key.
Then, we also need Instrumentation nodes.  For those, I thought we
could use some fixed, high-numbered key, and Tom's idea.

Are there extensions that use planner_hook to do surgery on the plan
tree?  What do they do, exactly?

-- 
Robert Haas
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