Re: misleading error message in ProcessUtilitySlow T_CreateStatsStmt

jian he <jian.universality@gmail.com>

From: jian he <jian.universality@gmail.com>

To: Álvaro Herrera <alvherre@kurilemu.de>

Cc: Tom Lane <tgl@sss.pgh.pa.us>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Kirill Reshke <reshkekirill@gmail.com>

Date: 2025-09-04T04:54:37Z

Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

CREATE STATISTICS: improve misleading error message
- cbd3732cbbaa 14.20 landed
- 4529861cc408 15.15 landed
- f30c04682cdf 16.11 landed
- f9b41f3e1ecd 17.7 landed
- 38883916e41c 18.0 landed
- 9ec0b29976b6 19 (unreleased) landed
- f9a7622483c3 15.15 landed
- f225473cbae2 19 (unreleased) landed
- e9fb314c7ad8 17.7 landed
- d84a6c3dad1f 16.11 landed
- b830f9d67463 14.20 landed
- 3eea4dc2c7cf 18.0 landed
Glossary: improve definition of "relation"
- 16a9165ce4a4 19 (unreleased) landed
Extended statistics on expressions
- a4d75c86bf15 14.0 cited

Attachments

v3-0001-refactor-CreateStatsStmt.patch (text/x-patch) patch v3-0001

On Fri, Aug 29, 2025 at 8:48 PM Álvaro Herrera <alvherre@kurilemu.de> wrote:
>
> > > 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.
>
> Yeah, I like how this turned out.  I found out this was introduced in
> commit a4d75c86bf15.

Previously, CreateStatistics and ProcessUtilitySlow opened the same relation
twice with a ShareUpdateExclusiveLock.  This refactor ensures the relation is
opened with ShareUpdateExclusiveLock only once and also reduces redundant error
checks.
The logic is now more intuitive: we first error checking
CreateStatsStmt->relations and then call transformStatsStmt to parse analysis
CreateStatsStmt->exprs.

please check the attached refactor CreateStatsStmt.