On 2018/07/05 9:40, Andres Freund wrote:
> On 2018-07-02 17:14:14 +0900, Amit Langote wrote:
>> I studied this a bit and found a bug that's causing the crash.
>>
>> The above mentioned commit has this hunk:
>>
>> @@ -1309,6 +1311,9 @@ hypothetical_dense_rank_final(PG_FUNCTION_ARGS)
>> PG_RETURN_INT64(rank);
>>
>> osastate = (OSAPerGroupState *) PG_GETARG_POINTER(0);
>> + econtext = osastate->qstate->econtext;
>> + if (!econtext)
>> + osastate->qstate->econtext = econtext =
>> CreateStandaloneExprContext();
>>
>> In CreateStandloneExprContext(), we have this:
>>
>> econtext->ecxt_per_query_memory = CurrentMemoryContext;
>>
>> /*
>> * Create working memory for expression evaluation in this context.
>> */
>> econtext->ecxt_per_tuple_memory =
>> AllocSetContextCreate(CurrentMemoryContext,
>> "ExprContext",
>> ALLOCSET_DEFAULT_SIZES);
>>
>> I noticed when debugging the crashing query that CurrentMemoryContext is
>> actually per-tuple memory context of some expression context of the
>> calling code, which would get reset before getting here again. So, it's
>> wrong of hypothetical_dense_rank_final to call CreateStandloneExprContext
>> without first switching to an actual per-query context.
>>
>> Attached patch seems to fix the crash.
>
> Thanks, that looks correct. Pushed!
Thank you.
Regards,
Amit
