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.
[...] From what i have learned, in most cases, there is a fixed small set of quite stable (not changed often) attributes which are used every time packet is processed. It might be better to have it loaded in one query together with credentials/domainid, (or even stored in domain cache). Having attributes in one row with user credentials is not something unusual, expression like modparam("avpops","db_scheme","email_scheme:table=subscriber;value_col=email_address;value_type=string") is common in many scripts.
There is no need to store any attributes in the credentials table. You can get everything with one query from both credentials and user_attrs tables like this:
mysql> select c.uid, c.password, a.name, a.value from credentials as c, user_attrs as a where auth_username='abc' and a.uid=c.uid; +-----+----------+------------------+---------------------+ | uid | password | name | value | +-----+----------+------------------+---------------------+ | 2 | heslo | datetime_created | 2009-04-06 16:44:18 | +-----+----------+------------------+---------------------+ 1 row in set (0.00 sec)
In the example above columns uid and password come from table credentials, columns name and value are the AVPs for the user stored in user_attrs table.
Minimizing the number of queries per SIP message is something I have had on my todo list for quite a while, including the optimization above. I have done some private experiments with this stuff and managed to cut the number of queries down to 2 per SIP message with MySQL. Those two queries loaded all the attributes, digest credentials, URIs and contacts from location table.
So yes, cutting down the number of queries is another thing worth doing. I did not want throw this in yet because we haven't agreed on a database schema and having a databases schema that supports this efficiently is a precondition for such optimizations. So right now we need to agree on the database schema for sip-router.
Jan.