Added the ability to forcibly set NULL for fields in settings proxy_mysql_query_rule

[identw]

Pull Request (PR) description

I found not convenient behavior:

Suppose a rule with digest has been configured:

   proxy_mysql_query_rule { "mysql_query_rule-1":
            rule_id               => 1,
            active                => 1,
            digest                => '0xDBF868B2AA296BC5',
            destination_hostgroup => 2,
            apply                 => 1,
   }

It creates in proxysql such a rule:

Admin> SELECT rule_id,match_pattern,digest FROM mysql_query_rules WHERE rule_id = 1 AND match_pattern IS NULL;
+---------+---------------+--------------------+
| rule_id | match_pattern | digest             |
+---------+---------------+--------------------+
| 1       | NULL          | 0xDBF868B2AA296BC5 |
+---------+---------------+--------------------+

NOTE: match_pattern is real NULL
Then I replace digest to match_pattern:

   proxy_mysql_query_rule { "mysql_query_rule-1":
            rule_id               => 1,
            active                => 1,
            match_pattern         => '^SELECT',
            destination_hostgroup => 2,
            apply                 => 1,
   }

Then:

+---------+---------------+--------------------+
| rule_id | match_pattern | digest             |
+---------+---------------+--------------------+
| 1       | ^SELECT       | 0xDBF868B2AA296BC5 |
+---------+---------------+--------------------+

But I would like to have digest equal NULL =(.

I tried to set digest to undef:

proxy_mysql_query_rule { "mysql_query_rule-1":
    rule_id               => 1,
    active                => 1,
    digest                => undef,
    match_pattern         => '^SELECT',
    destination_hostgroup => 2,
    apply                 => 1,
}

Then:

Admin> SELECT rule_id,match_pattern,digest FROM mysql_query_rules WHERE rule_id = 1;
+---------+---------------+--------------------+
| rule_id | match_pattern | digest             |
+---------+---------------+--------------------+
| 1       | ^SELECT       | 0xDBF868B2AA296BC5 |
+---------+---------------+--------------------+
1 row in set (0.00 sec)

But digest not changed =(.

I tried to set digest to NULL:

   proxy_mysql_query_rule { "mysql_query_rule-1":
            rule_id               => 1,
            active                => 1,
            digest                => 'NULL',
            match_pattern         => '^SELECT',
            destination_hostgroup => 2,
            apply                 => 1,
   }

Then:

Admin> SELECT rule_id,match_pattern,digest FROM mysql_query_rules WHERE rule_id = 1;
+---------+---------------+--------+
| rule_id | match_pattern | digest |
+---------+---------------+--------+
| 1       | ^SELECT       | NULL   |
+---------+---------------+--------+

But digest is not real NULL =(:

Admin> SELECT rule_id,match_pattern,digest FROM mysql_query_rules WHERE rule_id = 1 AND digest IS NULL;
Empty set (0.00 sec)
Admin> 

I corrected this behavior with my edit. Now when setting NULL, the real NULL value is written into the proxysql:

   proxy_mysql_query_rule { "mysql_query_rule-1":
            rule_id               => 1,
            active                => 1,
            digest                => 'NULL',
            match_pattern         => '^SELECT',
            destination_hostgroup => 2,
            apply                 => 1,
   }

Admin> SELECT rule_id,match_pattern,digest FROM mysql_query_rules WHERE rule_id = 1 AND digest IS NULL;
+---------+---------------+--------+
| rule_id | match_pattern | digest |
+---------+---------------+--------+
| 1       | ^SELECT       | NULL   |
+---------+---------------+--------+
1 row in set (0.00 sec)

Admin> 

This Pull Request (PR) fixes the following issues

[alexjfisher]

Seems to work ok. Thanks! There's a small limitation in that if the value has already been set to the string 'NULL' puppet will think it is already insync and won't attempt to fix it.

[alexjfisher]

@identw Thanks again. Sorry it took so long to review and merge.