| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Noah Misch <noah(at)leadboat(dot)com>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Simon Riggs <simon(at)2ndquadrant(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: postgres_fdw vs. force_parallel_mode on ppc |
| Date: | 2016-03-04 15:33:41 |
| Message-ID: | 5781.1457105621@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> Sure. If you have an idea what the right thing to do is, please go
> ahead.
Yeah, I'll modify the patch and commit sometime later today.
> I actually don't have a clear idea what's going on here. I
> guess it's that the wait_for_stats() guarantees that the stats message
> from the index insertion has been received but the status messages
> from the "trunc" tables might not have gotten there yet.
That's what it looks like to me. I now think that the apparent
connection to parallel query is a mirage. The reason we've only
seen a few cases so far is that the flapping test is new: it
wad added in commit d42358efb16cc811, on 20 Feb. If we left it
as-is, I think we'd eventually see the same failure without forcing
parallel mode. In fact, that's pretty much what you describe below,
isn't it? The pg_sleep is sort of half-bakedly substituting for
a proper wait.
regards, tom lane
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