Re: SELECT ... FOR UPDATE OF

On Thu, Dec 17, 2020 at 5:29 AM PG Doc comments form <noreply(at)postgresql(dot)org>
wrote:

> The following documentation comment has been logged on the website:
>
> Page: https://www.postgresql.org/docs/13/sql-select.html
> Description:
>
> The FOR UPDATE clause of the SELECT statement can be followed by an OF
> clause, but this is never explained at all in the documentation, as far as
> I
> can tell. What does it do? This needs to be written down.
>

It is. "If specific tables are named in a locking clause, then only rows
coming from those tables are locked;"

> For example, when attempting to use the OF clause in a particular query, I
> get the error "FOR UPDATE must specify unqualified relation names". The
> documentation doesn't provide enough information for me to understand what
> I
> have done wrong, so I will have to use trial and error to solve my problem.
>

A relation name is qualified if it has a schema in front of it. I'll agree
that the docs don't indicate that "table_name" has to be unqualified. But
mostly the OF clause points to the relations named within the query itself,
not to the original relation as recorded in the catalog.

David J.