On Fri, Sep 25, 2009 at 1:04 PM, Jan Janak jan@ryngle.com wrote:
On Fri, Sep 25, 2009 at 12:17 AM, Grzegorz Stanislawski stangrze@netitel.pl wrote:
Maybe we could start by implementing the easier version, that would give us the possibility to configure the query string but not its parameters. That's trivial to implement. Later we could add support for arbitrary parameters that are resolved to AVPs, selects, PVs, whatever.
Version capable of resolving variables would be very useful for accounting, and this is actually already done for db_extra modparam.
While having variable resolving for lookup queries might be overkill especially that in some cases some PVs or AVPs are not yet known which may lead to errors and confusion, i'd suggest not to trivialize it to syntax of mysql_prepare. Having well defined %1 %2 or something like this, would allow to for example use "select .. from credentials where user=%1 and domain=%2" when multidomain support is enabled and "select .. .. where user=%1" when not. simple parser in module init could change % macros to ? and add certain keys to list for further execution.
That's not trivial to implement anymore, unlike my simplified proposal with '$' above. It's not only about the parser, you have to change the way how you pass parameters to the query in the module and that's the more complicated part. I am not saying that it is difficult to do, but it takes some planning and coding.
And if we eventually do something like this, I'd prefer to do that one little extra step and implement support for selects, PVs, and AVPs instead of escape sequences like %1 and %2. The query from your example might then look like this:
select ... where user=@authorization.username and domain=@from.uri.host
Internally escape sequences like %1 and %2 would almost always be resolved to selects or PVs anyway simply because there are so many of them, they are convenient to use and they can extract almost anything from SIP messages or the proxy environment.
And I forgot to mention that patches are very much welcome, so if you implement any of this, I'd be happy to include it.
Thanks! Jan.