| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> |
| Cc: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Yuzuko Hosoya <hosoya(dot)yuzuko(at)lab(dot)ntt(dot)co(dot)jp>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Runtime pruning problem |
| Date: | 2019-04-17 03:54:01 |
| Message-ID: | 2018.1555473241@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> writes:
> On 2019/04/17 11:29, David Rowley wrote:
>> Where do you think the output list for EXPLAIN VERBOSE should put the
>> output column list in this case? On the Append node, or just not show
>> them?
> Maybe, not show them?
Yeah, I think that seems like a reasonable idea. If we show the tlist
for Append in this case, when we never do otherwise, that will be
confusing, and it could easily break plan-reading apps like depesz.com.
What I'm more worried about is whether this breaks any internal behavior
of explain.c, as the comment David quoted upthread seems to think.
If we need to have a tlist to reference, can we make that code look
to the pre-pruning plan tree, rather than the planstate tree?
regards, tom lane
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