Re: BUG #6222: Segmentation fault on unlogged table

On Mon, Sep 26, 2011 at 11:08 AM, Robert Haas <robertmhaas@gmail.com> wrote:
> On Mon, Sep 26, 2011 at 11:40 AM, Robert Haas <robertmhaas@gmail.com> wro=
te:
>> 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)
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0Datum =A0 =A0 =A0 =A0 =A0 expr_value;
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0bool =A0 =A0 =A0 =A0 =A0 =A0isNull;
>>
>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 Assert(!IsA(clause, List));
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0expr_value =3D ExecEvalExpr(clause, econt=
ext, &isNull, NULL);
>>
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0if (isNull)
>>
>> And in fact the test case (when run against the unlogged tables) fails
>> that assertion:
>>
>> TRAP: FailedAssertion("!(!((((Node*)(clause))->type) =3D=3D 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. =A0But on the very next commit
> I can:
>
> commit e6faf910d75027bdce7cd0f2033db4e912592bcc
> Author: Tom Lane <tgl@sss.pgh.pa.us>
> Date: =A0 Fri Sep 16 00:42:53 2011 -0400
>
> =A0 =A0Redesign the plancache mechanism for more flexibility and efficien=
cy.
>
> 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."

merlin