Re: proposal: session server side variables

From: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
To: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
Cc: Craig Ringer <craig(at)2ndquadrant(dot)com>, Fabrízio de Royes Mello <fabriziomello(at)gmail(dot)com>, Joe Conway <mail(at)joeconway(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: proposal: session server side variables
Date: 2016-12-28 15:42:28
Message-ID: alpine.DEB.2.20.1612281629270.4911@lancre
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Hello,

>> Why should they? If it is a session variable, being created when needed or
>> used with the right type could be enough?
>
> You cannot to trust some fuzzy object - or you have to play hard game with
> securing content - hashing, coding, decoding - it is slow, cpu intensive

I'm afraid that I do not understand. I do not think that a hash get in
memory is particularly costly. I do not see how you could do less that
that to manage variables with associated values.

>> Currently the big issue of plpgsql_check is work with temporary tables.
>
> No, I mean so when you use temporary tables inside plpgsql functions, then
> the static analyze like plpgsql check is almost impossible.

> I cannot to speak instead you, but lot of people prefer static analyze of
> code.

Hmmm... I know a little bit about that field, ISTM that you are speaking
of the current capabilities of a particular static analysis tool, but I'm
not sure that the tool capabilities could not be enhanced to manage more
things.

> The static analyze can be done only on static (persistent metadata).

A session variable is a bit like a global temporary variable. A static
analysis tool could take into account a global temporary variable.

> You cannot do it with dynamic (unfixed in schema) objects.

The private session variables I suggested have a fixed (static) name, and
their type could be infered by a static analysis tool, eg:

...
DECLARE @foo BOOLEAN PRIVATE;
-- I know that there is private a boolean variable "@foo" of unknown value
SET @foo = TRUE;
--- I know that @foo is true...
...

--
Fabien.

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