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

On Thu, Jun 28, 2018 at 5:28 AM, Yugo Nagata <nagata(at)sraoss(dot)co(dot)jp> 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.
>
> Attached is the patch to fix the error message. In this fix, column number
> is checked first. After applying this, the message is changed as below;
>
> postgres=# alter index idx alter column 2 set statistics 10;
> ERROR: cannot alter statistics on included column "d" of index "idx"

I think you should add an open item for this.

--
Robert Haas
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