From: | Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> |
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To: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Andres Freund <andres(at)2ndquadrant(dot)com>, Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com>, Amit Langote <amitlangote09(at)gmail(dot)com>, Fabrízio Mello <fabriziomello(at)gmail(dot)com>, Thom Brown <thom(at)linux(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Parallel Seq Scan |
Date: | 2015-03-13 08:42:08 |
Message-ID: | 5502A2E0.2080900@lab.ntt.co.jp |
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Lists: | pgsql-hackers |
On 13-03-2015 PM 05:32, Amit Langote wrote:
> On 12-03-2015 PM 11:46, Amit Kapila wrote:
>> [parallel_seqscan_v10.patch]
>
> There may be a bug in TupleQueueFunnelNext().
>
> 1) I observed a hang with stack looking like:
>
> #0 0x00000039696df098 in poll () from /lib64/libc.so.6
> #1 0x00000000006f1c6a in WaitLatchOrSocket (latch=0x7f29dc3c73b4,
> wakeEvents=1, sock=-1, timeout=0) at pg_latch.c:333
> #2 0x00000000006f1aca in WaitLatch (latch=0x7f29dc3c73b4, wakeEvents=1,
> timeout=0) at pg_latch.c:197
> #3 0x000000000065088b in TupleQueueFunnelNext (funnel=0x17b4a20, nowait=0
> '\000', done=0x17ad481 "") at tqueue.c:269
> #4 0x0000000000636cab in funnel_getnext (funnelstate=0x17ad3d0) at
> nodeFunnel.c:347
> ...
> <snip>
>
> 2) In some cases, there can be a segmentation fault with stack looking like:
>
> #0 0x000000396968990a in memcpy () from /lib64/libc.so.6
> #1 0x00000000006507e7 in TupleQueueFunnelNext (funnel=0x263c800, nowait=0
> '\000', done=0x2633461 "") at tqueue.c:233
> #2 0x0000000000636cab in funnel_getnext (funnelstate=0x26333b0) at
> nodeFunnel.c:347
> #3 0x0000000000636901 in ExecFunnel (node=0x26333b0) at nodeFunnel.c:179
> ...
> <snip>
>
> I could get rid of (1) and (2) with the attached fix.
Hit send too soon!
By the way, the bug seems to be exposed only with a certain pattern/sequence
of workers being detached (perhaps in immediate successive) whereby the
funnel->nextqueue remains incorrectly set.
The patch attached this time.
By the way, when I have asserts enabled, I hit this compilation error:
createplan.c: In function ‘create_partialseqscan_plan’:
createplan.c:1180: error: ‘Path’ has no member named ‘path’
I see following line there:
Assert(best_path->path.parent->rtekind == RTE_RELATION);
Thanks,
Amit
Attachment | Content-Type | Size |
---|---|---|
TupleQueueFunnelNext-bugfix.patch | text/x-diff | 878 bytes |
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