Creating an SQL join in Mediawiki's php framework - php

Question

Background:
Mediawiki's PHP framework provides functions for creating SQL statements to be executed against the application. Creating a simple SELECT FROM WHERE statement is easy and well documented, but I'm trying to create a JOIN statement and I don't understand the documentation. The examples are fragmented and disjointed.
Current attempt:
The SQL I'm trying to recreate is as follows. Using phpmyadmin I've tested this code and it returns the results I need:
SELECT user.user_id, user.user_name, user.user_real_name, user.user_email
FROM user
LEFT JOIN ipblocks ON user.user_id = ipblocks.ipb_user
WHERE ipblocks.ipb_id IS NULL
Translating this into Mediawiki's framework looks something like this, but this code doesn't work. The function documentation is here.
$result = $this->dbr->select(
array( $this->dbr->tableName( 'user' )),
array( 'user_name', 'user_id', 'user_email' ),
array( 'ipb_id' => 'NULL'),
__METHOD__,
array( 'GROUP_BY' => 'user_id DSC' ),
array( 'ipblocks' => array( 'LEFT JOIN', 'user_id=ipb_user' ) )
);
The SQL generated by this code can be checked by calling selectSQLText() instead. This function returns the generated SQL rather than executing it. The calling convention is the same. THis results in the following SQL:
SELECT user_name,user_id,user_email
FROM `user`
WHERE ipb_id = 'NULL'
I can see why the function has returned this, but I don't understand why the last two parameters have been ignored. The GROUP_BY and JOIN parts have been ignored. Why is this and how do I correct the code?
Thanks.

Answer 1

I'm not an user of Mediawiki, I've just glossed over the function documentation. As for grouping, I believe you should use GROUP BY array key, not GROUP_BY. As for joins, I think you must include ipblocks table in $table parameter in order to use it in $join_conds.
So, try this:
$result = $this->dbr->select(
array( 'user', 'ipblocks' ),
array( 'user_name', 'user_id', 'user_email' ),
array( 'ipb_id' => null),
__METHOD__,
array( 'GROUP BY' => 'user_id DSC' ),
array( 'ipblocks' => array( 'LEFT JOIN', 'user_id=ipb_user' ) )
);