Re: misleading error message in ProcessUtilitySlow T_CreateStatsStmt

On Fri, Aug 29, 2025 at 5:46 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> =?utf-8?Q?=C3=81lvaro?= Herrera <alvherre@kurilemu.de> writes:
> > I propose to use this report:
>
> > ERROR:  cannot create statistics on specified relation
> > DETAIL:  CREATE STATISTICS only supports tables, materialized views, foreign tables, and partitioned tables.
>
> WFM, although I think you could shorten it to "tables, materialized
> views, and foreign tables".  We generally expect that partitioned
> tables are included when saying "tables", no?  I'm not dead set on
> that either way, though.
>

https://www.postgresql.org/docs/current/sql-copy.html
use "COPY TO can be used only with plain tables, not views, and does
not copy rows from child tables or child partitions"

>
> Alternatively, maybe the right fix is to move the parse-analysis
> work into CreateStatistics altogether.  I think there is not a
> very good argument for ProcessUtilitySlow doing all that stuff.
> It's supposed to mainly just be a dispatching switch(), IMO.
>
seems doable.
transformStatsStmt, CreateStatistics both used only twice, refactoring arguments
should be fine.
please check the attached POC, regress tests also added.

main idea is
first check CreateStatsStmt->relations,
then call transformStatsStmt, transformStatsStmt only to transform
CreateStatsStmt->exprs.
also the above complaint about the relation lock issue will be resolved.