Mysql – Large accounting table, best way to partitioning by two dates


I need to create a log table to stores the connections to out network (last 3 years, after that the log will go into backup). The hardware/software used is proprietary, and for accounting it just call our custom script with some arguments like this:

  • when a user connects (our_script START user mac ip);
  • when a user disconnects (our_script STOP user mac ip in_bytes out_bytes more)

Sometimes we do not receive the disconnect message. So we need to adapt to this.

So far I came up with this structure for the accounting table:

CREATE TABLE `accounting` (
  `user` varchar(50) NOT NULL DEFAULT '',
  `mac` varchar(20) NOT NULL DEFAULT '',
  `ip` varchar(15) NOT NULL DEFAULT '',
  `ipv6` varchar(39) DEFAULT NULL,
  `start_datetime` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  `stop_datetime` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  `in_bytes` bigint(32) unsigned DEFAULT '0',
  `out_bytes` bigint(32) unsigned DEFAULT '0',
  `more_columns` varchar(255) default NULL, 
  PRIMARY KEY (`user`,`mac`,`ip`,`start_datetime`,`stop_datetime`),
  KEY `prim_ipv6` (`user`,`mac`,`ipv6`,`start_datetime`,`stop_datetime`),
  KEY `user` (`user`) USING HASH,
  KEY `mac` (`mac`) USING HASH,
  KEY `ip` (`ip`) USING HASH,
  KEY `ipv6` (`ipv6`) USING HASH,
  KEY `start_datetime` (`start_datetime`),
  KEY `stop_datetime` (`stop_datetime`)

The query used for writing are (these needs to be real fast):

  • when a user connects a simple insert
  • when a user disconnects update accounting set stop_datetime=now(), in_bytes=$in_bytes, out_bytes=$out_bytes, more_columns=$more where user="$user" and ip="$ip" and stop_datetime="0000-00-00 00:00:00" order by start_datetime DESC limit 1;, this is a workaround in the case we have more then one row for start, we just update the last start.

A better workaround, is to update the stop_datetime for rows without it, at every start, and use another column for storing that this is not a normal stop, I think I will go with the second workaround.

We have 2 ways to select from this table (this could be slower max 1 – 2 sec):

  • select the last 50 connection for a user: select ... where user="$user" order by start_datetime DESC limit 50;, for this the user HASH key is handy, beacause AFAIK HASH is better than BTREE for equality.
  • select witch user was connected with ip=$ip on date=$date select ... where ip="$ip" and $date between start_datetime and stop_datetime;

This table will hold between 0.5 to 1 bilion rows, that's why I thought to partition it.
The best option is to partition it by month, but I have 2 relevant dates, and at the begining/end of the month start will be in one partition, stop will be in another.

The questions:

  • Witch is the best way to do partitions, by start_datetime, by stop_datetime, by start_datetime with subpartitions for stop_datetime ?

  • Do I realy need to partitionate ?

  • Do you have any other suggestion on how to improve this ?

Thank you

Best Answer

Since stop_datetime will not be known at insert time the partition must be done by start_datetime.

I think partitioning by day (date_format(start_datetime, '%Y-%m-%d')) would be adequate since 1 billion rows divided by (3 years * 365 days) ≃ 900,000 rows per partition

Updating indexes is expensive and it happens at inserts, updates and deletes. Keep the indexes to a minimum. If the main queries will be those selects then I would keep the primary key like the following and trash all the other keys:

PRIMARY KEY (`user`,`start_datetime`,`stop_datetime`,`mac`,`ip`)