Re: proposal: schema PL session variables

2016-02-12 22:41 GMT+01:00 Jim Nasby <Jim.Nasby@bluetreble.com>:

On 2/12/16 2:58 PM, Pavel Stehule wrote:

    So I think adding something like this needs to at least address
    *how* SQL level access would work, *when* it's eventually implemented.


I understand - and I agree.

small note: Private variables should not be executed from any SQL,
because SQL has not directly related schema. It can be executed only
from SQL embedded in some object with attached schema - PL functions,
views, constraints, .. So for this use case, the important information
is info about a container. We have to hold info about related schema in
planner/executor context.

I think that's probably true, but this also shows why we need to consider different PLs too. As it stands right now, the only way to access a variable outside of plpgsql would be to call a plpgsql function, and currently there's no way to make a plpgsql function private. So for this to work, private variables probably need to be exposed directly through the pl handler.

Again, I'm not saying this all has to be implemented up front, but there needs to be a plan for how it would work.

I think it would be a good idea to start a wiki page on this topic to start collecting stuff together.

I wrote some basic info - https://wiki.postgresql.org/wiki/CREATE_PRIVATE_VARIABLE

I changed my opinion on initialization part. The private variables with non null default should be initialized in session start. It is much more practical and it can be used for triggering some ON CONNECT custom routines.

Regards

Pavel

 

--
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
Data in Trouble? Get it in Treble! http://BlueTreble.com