Re: Server crashed with dense_rank on partition table.

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!

- Andres