Re: Fix error message when trying to alter statistics on included column

On 2018-Jun-28, Yugo Nagata wrote:

> According to the error message, it is not allowed to alter statistics on
> included column because this is "non-expression column".
> 
>  postgres=# create table test (i int, d int);
>  CREATE TABLE
>  postgres=# create index idx on test(i) include (d);
>  CREATE INDEX
>  postgres=# alter index idx alter column 2 set statistics 10;
>  ERROR:  cannot alter statistics on non-expression column "d" of index "idx"
>  HINT:  Alter statistics on table column instead.
> 
> However, I think this should be forbidded in that this is not a key column 
> but a included column. Even if we decide to support expressions in included
> columns in future, it is meaningless to do this because any statistics on 
> included column is never used by the planner.

I agree with this reasoning, so I pushed this patch.  Thanks!  I added a
couple of lines in the regress file for this feature also.

Teodor, Alexander, now would be the time to express dissent :-)

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
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