Re: BUG #15998: query to return a table column list gives error on amissing foreign data wrapper library

On Tue, Sep 10, 2019 at 6:46 PM PG Bug reporting form
<noreply@postgresql.org> wrote:
> Have been able to reproduce the behavior on postgres 10 and 11 with the
> postgres_fdw on centos 7 on ppc64le.
> Take a postgres database with foreign servers and foreign tables.
> remove the fdw library.
> i simulated this by
> mv postgres_fdw.so postgres_fdw.so.xx
>
> run the query below on a normal table
> the query needs to be adjusted to to have a table oid  (version runs in
> postgres 11)
> SELECT
>              typ.oid AS typoid, nspname, relname, attname, attrelid, attnum,
> attnotnull,
>              attidentity != '' AS isidentity,
>              CASE WHEN typ.typtype = 'd' THEN typ.typtypmod ELSE atttypmod
> END AS typmod,
>              CASE WHEN atthasdef THEN (SELECT pg_get_expr(adbin, cls.oid)
> FROM pg_attrdef WHERE adrelid = cls.oid AND adnum = attr.attnum) ELSE NULL
> END AS default,
>              CASE WHEN col.is_updatable = 'YES' THEN true ELSE false END AS
> is_updatable,
>              EXISTS (
>                SELECT * FROM pg_index
>                WHERE pg_index.indrelid = cls.oid AND
>                      pg_index.indisprimary AND
>                      attnum = ANY (indkey)
>              ) AS isprimarykey,
>              EXISTS (
>                SELECT * FROM pg_index
>                WHERE pg_index.indrelid = cls.oid AND
>                      pg_index.indisunique AND
>                      pg_index.indnkeyatts = 1 AND
>                      attnum = pg_index.indkey[0]
>              ) AS isunique
>         FROM pg_attribute AS attr
>         JOIN pg_type AS typ ON attr.atttypid = typ.oid
>           JOIN pg_class AS cls ON cls.oid = attr.attrelid
>         JOIN pg_namespace AS ns ON ns.oid = cls.relnamespace
>         LEFT OUTER JOIN information_schema.columns AS col ON
> col.table_schema = nspname AND
>              col.table_name = relname AND
>              col.column_name = attname
>         WHERE
>              atttypid <> 0 AND
>              relkind IN ('r', 'v', 'm') AND
>              NOT attisdropped AND
>              nspname NOT IN ('pg_catalog', 'information_schema') AND
>              attnum > 0 AND
>              ((attr.attrelid=1354075 AND attr.attnum=1))
> ORDER BY attnum
>
> throws error
> ERROR:  could not access file "$libdir/postgres_fdw": No such file or
> directory

I'm now traveling, so I cannot try to reproduce this.  Could you send
the EXPLAIN output for this query?

> commenting out the case statement
>  CASE WHEN col.is_updatable = 'YES' THEN true ELSE false END AS
> is_updatable,
>
> causes the query to run without error.

Seems reasonable to me; the is_updatable reference would cause the
IsForeignRelUpdatable() call for postgres_fdw foreign tables IIUC, so
removing that would be a workaround for this issue if that works for
you.

Best regards,
Etsuro Fujita