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Re: BUG #6222: Segmentation fault on unlogged table

From: Merlin Moncure <mmoncure(at)gmail(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, pgsql-bugs(at)postgresql(dot)org, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: BUG #6222: Segmentation fault on unlogged table
Date: 2011-09-26 16:17:04
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-bugs
On Mon, Sep 26, 2011 at 11:08 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Mon, Sep 26, 2011 at 11:40 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> To check my work, I did this:
>> --- a/src/backend/executor/execQual.c
>> +++ b/src/backend/executor/execQual.c
>> @@ -5003,6 +5003,7 @@ ExecQual(List *qual, ExprContext *econtext, bool
>> resultForNull)
>>                Datum           expr_value;
>>                bool            isNull;
>> +               Assert(!IsA(clause, List));
>>                expr_value = ExecEvalExpr(clause, econtext, &isNull, NULL);
>>                if (isNull)
>> And in fact the test case (when run against the unlogged tables) fails
>> that assertion:
>> TRAP: FailedAssertion("!(!((((Node*)(clause))->type) == T_List))",
>> File: "execQual.c", Line: 5006)
>> Now I'm not too sure why that is happening yet, but I'm leaning toward
>> the idea that the bug here is timing-related and that unlogged tables
>> aren't the cause, but rather just make it easier to hit whatever the
>> race condition is by removing some overhead.
> I cannot reproduce this on commit
> e6faf910d75027bdce7cd0f2033db4e912592bcc.  But on the very next commit
> I can:
> commit e6faf910d75027bdce7cd0f2033db4e912592bcc
> Author: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
> Date:   Fri Sep 16 00:42:53 2011 -0400
>    Redesign the plancache mechanism for more flexibility and efficiency.
> Tom, any thoughts?

hm. any relation to YAMAMOTO Takashi's recent email, [BUGS] bug in
plancache.c, which hasn't hit the archives yet?

> "GetCachedPlan can pass the 'qlist' to the planner twice.
if i understand the code correctly, it's unsafe because the planner is
destructive wrt the input tree.  for my application, it often causes
a crash in executor."


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Subject: Re: BUG #6222: Segmentation fault on unlogged table
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