MySQL, is there a way to tell when was database last changed/modified

MySQL

I'm creating MySQL dump of 5 databases every hour. 3 of those databases very rarely change, so creating a MySQL dump for those 3 dbs is pretty much a waste of time and resources.

Is there a way I can retrieve a unix epoch seconds of when a specific db was last changed/updated? I would compare it with latest dump file and only dump another one if there are changes.

So question again: How can I get the unix epoch datetime of last update/change of a specific database?

Best Answer

Only works for MyISAM tables

You can run a MySQL query against the information_schema table:

Example (replace dbname with your database name):

SELECT UNIX_TIMESTAMP(MAX(UPDATE_TIME)) as last_update 
FROM information_schema.tables 
WHERE TABLE_SCHEMA='dbname' 
GROUP BY TABLE_SCHEMA;

Related Solutions

MySQL connection spike out of nowhere

My guess is that you have some long running queries in your application. When they are executed they cause the connection to stay checked out of the pool for a long time (relative to the usual usage pattern), this causes your pool to become exhausted, grow, and continue to grow up to its maximum, at which point any remaining workers block waiting on connections to be released.

The first thing will be to track down when this happens, that is, is it a cyclical event, or random. If its the former you're in luck, as you can be ready time it happens. If you can't determine a pattern then you'll have to be vigilant.

You may be able to figure this from looking at your website monitoring logs, or sar from your database to see if there are any correlating spikes.

If you can catch your database when its under load, you should execute the following commands on the mysql server

show innodb status;
show processlist;

The former will print out diagnostic information about the innodb engine (you are using innodb right?), the latter will print out the first few hundred chars of the query that was executing. Look for queries that have been running for a long time, queries generating temporary tables on disk, and queries that are blocked on a resource.

After that, the hard work begins. Use EXPLAIN to estimate the cost of the query, and the resources it uses. Avoid queries that require sorting on disk via a tmp table. Look for long running reporting jobs, or other scheduled maintenance tasks that periodically lock or saturate your database. It could be something as simple as the backup task, or a job that rolls up old purchase order data.

I recommend having these three settings in your /etc/my.cnf

log_slow_queries
log-queries-not-using-indexes
set-variable = long_query_time=1

For a web application doing 20-30 requests per second, you can't afford to have anything show up in these logs.

btw, IMHO its pointless to increase your connection pool's size beyond your original size as this will only delay the onset of pool exhaustion by at best, a few seconds, and only put more pressure on your db right when it doesn't need it.

Mysql – How to tell if a MySQL database is being accessed

How about the query:

SHOW FULL PROCESSLIST

This will show you connections to the database, what user they are logged in with, the state of the connection, and any currently running command.

Best Answer

Related Solutions

MySQL connection spike out of nowhere

Mysql – How to tell if a MySQL database is being accessed

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