Re: Schema variables - new implementation for Postgres 15 - Mailing list pgsql-hackers

Hi,

On Tue, Jan 25, 2022 at 09:35:09AM +0100, Pavel Stehule wrote:
> út 25. 1. 2022 v 6:18 odesílatel Julien Rouhaud <rjuju123@gmail.com> napsal:
>
> > I think the lock should be
> > acquired during IdentifyVariable.  It should probably be optional as one
> > codepath only needs the information to raise a warning when a variable is
> > shadowed, so a concurrent drop isn't a problem there.
> >
>
> There is a problem, because before the IdentifyVariable call I don't know
> if the variable will be shadowed or not.
>
> If I lock a variable inside IdentifyVariable, then I need to remember if I
> did lock there, or if the variable was locked already, and If the variable
> is shadowed and if lock is fresh, then I can unlock the variable.

But in transformColumnRef() you already know if you found a matching column or
not when calling IdentifyVariable(), so you know if an existing variable will
shadow it right?

Couldn't you call something like

    lockit = node == NULL;
        varid = IdentifyVariable(cref->fields, &attrname, &not_unique, lockit);

The only other caller is transformLetStmt(), which should always lock the
variable anyway.