Remove changing volatile to singleqe for queries with outer quals

[red1452]

Remove changing volatile to singleqe for queries with outer quals

Function handle_gen_seggen_volatile_path is used in 6X to make single QE query
from queries on replicated tables with volatile function. It adds Motion and
Result nodes to make query at one segment correctly. In 7X it does not need to
do, because if query contains outer quals, nodes result and materialize will be
added by bring_to_outer_query.

Function handle_gen_seggen_volatile_path was not removed, because it contains
check, which restricts DML queries on replicated tables with filter, which
contains volatile functions.

Also, this patch adds tests from commit 7ef4218.

[Stolb27]

Please reword PR description. Why adding of Motion by the mentioned function is incorrect? Which consequences is leaded? The bring_to_outer_query is able to produce both kind of motions (Gather or Broadcast). What is the case when the handle_gen_seggen_volatile_path still needed that makes you to exclude it only partially?

[Stolb27]

Why does empty upperrestrictinfo sign that there is no outer queries?

[red1452]

I updated the comment above.

[Stolb27]

I see. You filtered out cases for bring_to_outer_query from this condition. Why problem manifests itself only in case of not null upperrestrictinfo? What are other cases to execute Segment General only on Single QE?

Function handle_gen_seggen_volatile_path was not removed, because it contains
check, which restricts DML queries on replicated tables with filter, which
contains volatile functions.

It's quite strange to leave complex transformation logic only for exact checks. Do we still needed these transformations?

[red1452]

Functions handle_gen_seggen_volatile_path, bring_to_outer_query and bring_to_singleQE make the same things, but in the different cases. Function handle_gen_seggen_volatile_path works when locus is general or segment general or replicated and there is volatile function. Function bring_to_outer_query works when locus is not general and not outer query and there is outer quals. Function bring_to_singleQE works when locus is not general and not entry and not single QE and not outer query.
I think removing or union of these functions must be done in the other ticket, which will be complex refactoring of it. My patch just fix double work of these functions, when handle_gen_seggen_volatile_path and bring_to_outer_query work together. It does not needed to execute function handle_gen_seggen_volatile_path if function bring_to_outer_query will be executed (in case of non null upperrestrictinfo).

[red1452]

One of some queries, which will be changed if handle_gen_seggen_volatile_path is removed:

create table t_hashdist(a int, b int, c int) distributed by (a);
create table t_replicate_volatile(a int, b int, c int) distributed replicated;
explain (costs off) select * from t_replicate_volatile, t_hashdist where t_replicate_volatile.a > random();

Plan before:

                              QUERY PLAN                              
----------------------------------------------------------------------
 Nested Loop
   ->  Gather Motion 3:1  (slice1; segments: 3)
         ->  Seq Scan on t_hashdist
   ->  Materialize
         ->  Result
               ->  Gather Motion 1:1  (slice2; segments: 1)
                     ->  Seq Scan on t_replicate_volatile
                           Filter: ((a)::double precision > random())
 Optimizer: Postgres query optimizer
(9 rows)

Plan after:

                        QUERY PLAN                        
----------------------------------------------------------
 Gather Motion 3:1  (slice1; segments: 3)
   ->  Nested Loop
         ->  Seq Scan on t_replicate_volatile
               Filter: ((a)::double precision > random())
         ->  Materialize
               ->  Seq Scan on t_hashdist
 Optimizer: Postgres-based planner
(7 rows)

[Stolb27]

Function handle_gen_seggen_volatile_path is used in 6X to make single QE query
from queries on replicated tables with volatile function. It adds Motion and
Result nodes to make query at one segment correctly.

In my opinion, the function transforms only part of query, not the whole one.