Обсуждение: Expression index with function based on current_user?

I have private tables such as this (Very simplified):
CREATE TABLE private.t_foo ( ...
);
REVOKE ALL ON private.t_foo FROM public;

Different users have access to different  data in the table, so I do 
this view:
CREATE VIEW foo AS SELECT * FROM private.t_foo WHERE private.haveaccess();
GRANT ALL ON foo TO public;

Using rules I then make the view updatable (In reality views fetch and 
write data to multiple tables usually). This works fine, but I have some 
thought on performance in the future.

The function private.haveaccess()'s result depends on the currently 
logged in user, is it still possible to create an expression index over 
that function?

// Fredrik Olsson

>
>The function private.haveaccess()'s result depends on the currently logged 
>in user, is it still possible to create an expression index over that 
>function?
>
>// Fredrik Olsson
>

Hello,

All functions and operators used in an index definition must be "immutable", 
that is, their results must depend only on their arguments and never on any 
outside influence. ... And your function is vollatile => you can't to do 
expression index.

Regards
Pavel Stehule

_________________________________________________________________
Emotikony a pozadi programu MSN Messenger ozivi vasi konverzaci. 
http://messenger.msn.cz/

Ühel kenal päeval, K, 2006-02-08 kell 12:26, kirjutas Fredrik Olsson:
> I have private tables such as this (Very simplified):
> CREATE TABLE private.t_foo (
>   ...
> );
> REVOKE ALL ON private.t_foo FROM public;
> 
> Different users have access to different  data in the table, so I do 
> this view:
> CREATE VIEW foo AS
>   SELECT * FROM private.t_foo WHERE private.haveaccess();
> GRANT ALL ON foo TO public;
> 
> Using rules I then make the view updatable (In reality views fetch and 
> write data to multiple tables usually). This works fine, but I have some 
> thought on performance in the future.
> 
> The function private.haveaccess()'s result depends on the currently 
> logged in user, is it still possible to create an expression index over 
> that function?

No, but you probably can crete index on static function
user_has_access(username) and then use that func in
private.haveaccess()

------------
Hannu

Fredrik Olsson <fredrik.olsson@treyst.se> writes:
> CREATE VIEW foo AS
>   SELECT * FROM private.t_foo WHERE private.haveaccess();
> GRANT ALL ON foo TO public;

If the function is parameterless as you show, what is it accomplishing
that could not be done with grant/revoke on the view?

If it is not parameterless, you had better be more specific about what
it depends on.
        regards, tom lane