| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Pushdown target list below gather node (WAS Re: WIP: Upper planner pathification) |
| Date: | 2016-03-17 13:40:50 |
| Message-ID: | 25837.1458222050@sss.pgh.pa.us |
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Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> writes:
> While reading above code changes, it looks like it is assuming that subpath
> and subplan will always be same (as it is verifying projection capability
> of subpath and attaching the tlist to subplan), but I think it is possible
> that subpath and subplan correspond to different nodes when gating Result
> node is added on to top of scan plan by create_scan_plan().
A little more thought will show you that that's not actually relevant,
because the tlist computation would have happened (or not) below the
gating Result. If gating Results had an impact on
apply_projection_to_path's decisions we'd have had to do something about
that before this.
regards, tom lane
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