Thread: BUG #16670: pgstattuple ERROR: relation "sql_implementation_info" does not exist

The following bug has been logged on the website:

Bug reference:      16670
Logged by:          Marc Rechté
Email address:      mrechte@gmail.com
PostgreSQL version: 13.0
Operating system:   CentOS8
Description:

Hello,

I get an error with pgstattuple extension.

On PG13.0:
# select tablename,
(pgstattuple_approx(tablename::regclass)).approx_free_space from pg_tables
where schemaname = 'public'  and
(pgstattuple_approx(tablename::regclass)).approx_free_percent > 10;
ERROR:  relation "sql_implementation_info" does not exist

On PG12.3:
# select tablename,
(pgstattuple_approx(tablename::regclass)).approx_free_space from pg_tables
where schemaname = 'public'  and
(pgstattuple_approx(tablename::regclass)).approx_free_percent > 10;
ERROR:  relation "sql_packages" does not exist

Note that the where clause on approx_free_percent is the error cause.

Thanks

PG Bug reporting form <noreply@postgresql.org> writes:
> # select tablename,
> (pgstattuple_approx(tablename::regclass)).approx_free_space from pg_tables
> where schemaname = 'public'  and
> (pgstattuple_approx(tablename::regclass)).approx_free_percent > 10;
> ERROR:  relation "sql_implementation_info" does not exist

This is not a bug.  We don't guarantee anything about the evaluation
order of WHERE clauses.  Even if we did, this query has got bugs of
its own: it will fail on tablenames that would require quoting,
such as names containing spaces, dots, uppercase letters, etc.

You could write

(quote_ident(schemaname)||'.'||quote_ident(tablename))::regclass

to avoid both of those issues.  There are still going to be some race
condition problems around just-dropped tables, though.

            regards, tom lane