Обсуждение: SESSION SESSION - bug or intentional?

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SESSION SESSION - bug or intentional?

От
Joe Conway
Дата:
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?

Joe

--
Crunchy Data - http://crunchydata.com
PostgreSQL Support for Secure Enterprises
Consulting, Training, & Open Source Development


Re: SESSION SESSION - bug or intentional?

От
"David G. Johnston"
Дата:
On Wed, Sep 30, 2015 at 2:52 PM, Joe Conway <mail@joeconway.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?

​Scanning the SET and SET TRANSACTION it doesn't appear to be something they are documented as allowing.

However, SET SESSION AUTHORIZATION is defined as thus:

SET [ SESSION | LOCAL ] SESSION AUTHORIZATION user_name

​which implies that we don't ​take pains to avoid it.  Since:

"The SESSION and LOCAL modifiers are a PostgreSQL extension, as is the RESET syntax."

The standard doesn't have any undue influence on our particular decision.

David J.


Re: SESSION SESSION - bug or intentional?

От
Tom Lane
Дата:
"David G. Johnston" <david.g.johnston@gmail.com> writes:
> On Wed, Sep 30, 2015 at 2:52 PM, Joe Conway <mail@joeconway.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.
        regards, tom lane



Re: SESSION SESSION - bug or intentional?

От
"David G. Johnston"
Дата:
On Wed, Sep 30, 2015 at 5:49 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
"David G. Johnston" <david.g.johnston@gmail.com> writes:
> On Wed, Sep 30, 2015 at 2:52 PM, Joe Conway <mail@joeconway.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?
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.