Re: Optimizing nested ConvertRowtypeExpr execution

On Mon, Apr 2, 2018 at 1:40 AM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> Hi,
>
> On 2018-02-26 17:20:05 +0530, Ashutosh Bapat wrote:
>> In a multi-level partitioned table, a parent whole-row reference gets
>> translated into nested ConvertRowtypeExpr with child whole-row
>> reference as the leaf. During the execution, the child whole-row
>> reference gets translated into all all intermediate parents' whole-row
>> references, ultimately represented as parent's whole-row reference.
>> AFAIU, the intermediate translations are unnecessary. The leaf child
>> whole-row can be directly translated into top parent's whole-row
>> reference. Here's a WIP patch which does that by eliminating
>> intermediate ConvertRowtypeExprs during ExecInitExprRec().
>
> Why is this done appropriately at ExecInitExpr() time, rather than at
> plan time? Seems like eval_const_expressions() would be a bit more
> appropriate (being badly named aside...)?

That seems to be a better idea. Here's patch.

--
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company