Re: SESSION SESSION - bug or intentional?

On Wed, Sep 30, 2015 at 5:49 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> "David G. Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> writes:
> > On Wed, Sep 30, 2015 at 2:52 PM, Joe Conway <mail(at)joeconway(dot)com> wrote:
> >> I was looking at something in gram.y when I noticed that the following
> >> production works:
> >> SET SESSION SESSION CHARACTERISTICS AS TRANSACTION READ ONLY;
> >> "SESSION SESSION" seems fairly odd -- is it intentional?
>
> > However, SET SESSION AUTHORIZATION is defined as thus:
> > SET [ SESSION | LOCAL ] SESSION AUTHORIZATION user_name
>
> Yeah. SET LOCAL SESSION AUTHORIZATION is valid and useful. The optional
> SESSION is just a noise word here, but disallowing it would be
> non-orthogonal compared to other similar syntaxes.
>

​While I get the gist of what you are saying the phrase:

"[...] but disallowing it would be non-orthogonal compared to other similar
syntaxes."

doesn't compute for me. You mind trying that again?

​I take it that means that disallowing it would be "inconsistent" given
what we allow in similar commands.​

Given that conclusion shouldn't the following be modified?
​http://www.postgresql.org/docs/devel/static/sql-set-transaction.html​
SET [ SESSION | LOCAL ] SESSION CHARACTERISTICS AS TRANSACTION
transaction_mode [, ...]

Both are allowed though the one is redundant and the other (presumably)
ignored, repsectively.

A code comment in the grammar would be warranted at the least - not going
there myself.

I haven't tried to figure out what exactly LOCAL results in if specified
vis-a-vis the presence of absence of an active transcation.

David J.