#463 EXECUTE DIRECT queries with particular GROUP BY clause return strange binary results.

[cbx]

The next query returns strange result.
EXECUTE DIRECT ON (datanode1) $$SELECT relkind FROM pg_class GROUP BY relname, relkind$$;

It should return like Table A, but it returns like Table B.

Table A

 relkind 
---------
 i
 r
 v
 t
(4 rows)

Table B

 relkind 
---------
 h


 \x18
 `


 8


 \x10
 X


 0
 x

 \x08
 P


 (
 p


 H

And next queries return the right results.

# execute direct on (datanode1) $$select relkind from pg_class group by relkind$$;
# execute direct on (datanode1) $$select relname, relkind from pg_class group by relname, relkind$$;

It seems that this problem is produced when select target does not contain all of the columns listed in the GROUP BY clause.

[cbx]

A query to a regular table work well.

cx=# create table tbl as select generate_series(1,10) as a, generate_series(1,10) as b;
INSERT 0 10
cx=# execute direct on (datanode2) $$select b from tbl group by a,b$$;
 b  
----
  7
 10
  4
  3
(4 rows)

On master_pg93_merge, this issue may cause psql disconnection.

cx=# execute direct on (datanode1) $$select tablename from pg_catalog.pg_tables group by schemaname,tablename$$;
The connection to the server was lost. Attempting reset: Failed.
!>

This query doesn't make coordinator to be aborted.

[cbx]

A datanode is returning the right result but a coordinator is returning wrong result.
I think this issue is bug of coordinator.