Re: misleading error message in ProcessUtilitySlow T_CreateStatsStmt

Kirill Reshke <reshkekirill@gmail.com>

From: Kirill Reshke <reshkekirill@gmail.com>

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

Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>

Date: 2025-08-21T15:20:52Z

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

On Thu, 21 Aug 2025 at 17:00, jian he <jian.universality@gmail.com> wrote:
>
> hi.

Hi!

>   RangeVar   *rel = (RangeVar *) linitial(stmt->relations);
>   if (!IsA(rel, RangeVar))

These two lines are weird. Looks like  linitial(stmt->relations)
should be assigned to variable with type Node* first?

>
> for example:
>
> create or replace function tftest(int) returns table(a int, b int) as $$
> begin
>   return query select $1, $1+i from generate_series(1,5) g(i);
> end;
> $$ language plpgsql immutable strict;
>
> CREATE STATISTICS alt_stat2 ON a, b FROM tftest(1);
> ERROR:  only a single relation is allowed in CREATE STATISTICS
>
> this error message seem misleading?

I wouldn’t say this is misleading, but " a single relation" is indeed
not precise enough. IMO we need a more precise term to distinguish
regular relation and table func.

> also this error check seems duplicated in CreateStatistics?
>

Indeed.

-- 
Best regards,
Kirill Reshke