Re: [PATCH] Erase the distinctClause if the result is unique by definition

On Tue, Feb 11, 2020 at 12:22 AM Ashutosh Bapat <ashutosh.bapat.oss@gmail.com> wrote:

[PATCH] Erase the distinctClause if the result is unique by
 definition

I forgot to mention this in the last round of comments. Your patch was actually removing distictClause from the Query structure. Please avoid doing that. If you remove it, you are also removing the evidence that this Query had a DISTINCT clause in it.

Yes, I removed it because it is the easiest way to do it.  what is the purpose of keeping the evidence?

Suppose after a DDL, the prepared statement need to be re-parsed/planned 

if it is not executed or it will prevent the DDL to happen.  

-- session 2

postgres=# alter table t alter column b drop not null;
ALTER TABLE

-- session 1:

postgres=# explain execute st(1);
                         QUERY PLAN
-------------------------------------------------------------
 Unique  (cost=1.03..1.04 rows=1 width=4)
   ->  Sort  (cost=1.03..1.04 rows=1 width=4)
         Sort Key: b
         ->  Seq Scan on t  (cost=0.00..1.02 rows=1 width=4)
               Filter: (c = $1)
(5 rows)