Re: Optimizing nested ConvertRowtypeExpr execution

On Tue, Apr 3, 2018 at 10:48 AM, Ashutosh Bapat
<ashutosh(dot)bapat(at)enterprisedb(dot)com> wrote:
>>
>> 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.
>

Previous patch didn't try to fold the ConvertRowtypeExpr::arg into a Const.

postgres=# create table t1 (a int, b int, c int) partition by range(a);
postgres=# create table t1p1 partition of t1 for values from (0) to
(100) partition by range(b);
postgres=# create table t1p1p1 partition of t1p1 for values from (0) to (50);
postgres=# explain verbose select (1, 2, 3)::t1p1p1::t1p1::t1; --
notice Rowexpression here.
QUERY PLAN
-------------------------------------------
Result (cost=0.00..0.01 rows=1 width=32)
Output: (ROW(1, 2, 3)::t1p1p1)::t1
(2 rows)

Here's patch fixing that. With this patch
postgres=# explain verbose select (1, 2, 3)::t1p1p1::t1p1::t1;
QUERY PLAN
-------------------------------------------
Result (cost=0.00..0.01 rows=1 width=32)
Output: '(1,2,3)'::t1
(2 rows)

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