| From: | Stephen Frost <sfrost(at)snowman(dot)net> |
|---|---|
| To: | Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com>, Kohei KaiGai <kaigai(at)kaigai(dot)gr(dot)jp>, Shigeru Hanada <shigeru(dot)hanada(at)gmail(dot)com>, Jim Mlodgenski <jimmy76(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PgHacker <pgsql-hackers(at)postgresql(dot)org>, Peter Eisentraut <peter_e(at)gmx(dot)net> |
| Subject: | Re: Custom Scan APIs (Re: Custom Plan node) |
| Date: | 2014-03-04 14:23:45 |
| Message-ID: | 20140304142345.GC12995@tamriel.snowman.net |
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| Lists: | pgsql-hackers |
* Ashutosh Bapat (ashutosh(dot)bapat(at)enterprisedb(dot)com) wrote:
> During EXPLAIN, ExecInitNode() is called. If ExecInitNode() fires queries
> to foreign servers, those would be fired while EXPLAINing a query as well.
> We want to avoid that. Instead, we can run EXPLAIN on that query at foreign
> server. But again, not all foreign servers would be able to EXPLAIN the
> query e.g. file_fdw. OR totally avoid firing query during ExecInitNode(),
> if it's for EXPLAIN (except for ANALYSE may be).
Agreed that we wouldn't want to actually run a query when it's just
being explain'd. If the FDW can't tell the difference then we'd need to
address that, of course. A similar issue would, presumably, be around
prepare/execute, though I haven't looked yet. These kinds of issues are
why it was option '#2' instead of '#1'. :) I'm not sure they're able to
be addressed. :/
Thanks,
Stephen
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