Finding fragmented MySQL tables and optimising them - bash script

Via here


Note: if you just want to find fragmented tables and don't want to optimise, just comment out the "OPTIMIZE TABLE" line in the script below

#!/bin/sh

echo -n "MySQL username: " ; read username
echo -n "MySQL password: " ; stty -echo ; read password ; stty echo ; echo

mysql -u $username -p"$password" -NBe "SHOW DATABASES;" | grep -v 'lost+found' | while read database ; do
mysql -u $username -p"$password" -NBe "SHOW TABLE STATUS;" $database | while read name engine version rowformat rows avgrowlength datalength maxdatalength indexlength datafree autoincrement createtime updatetime checktime collation checksum createoptions comment ; do
if [ "$datafree" -gt 0 ] ; then
fragmentation=$(($datafree * 100 / $datalength))
echo "$database.$name is $fragmentation% fragmented."
mysql -u "$username" -p"$password" -NBe "OPTIMIZE TABLE $name;" "$database"
fi
done
done

Find fragmented tables in MySQL

Via Mindraven:

Over time some of your MySQL tables may end up fragmented. If you run any type of diagnostic script like mysqltuner, it will even tell you how many of your tables are fragmented. You can easily fix this by optimizing the fragmented tables. The problem is, you might not know which tables are fragmented.

Here’s a quick little query you can run that will give you the tables that are fragmented and how badly fragmented they are:

select TABLE_NAME, TABLE_SCHEMA, Data_free from information_schema.TABLES where TABLE_SCHEMA NOT IN ('information_schema', 'mysql') and Data_Free >0;

Just in case anyone didn’t catch the optimize bit above. Once you’ve found your fragmentend tables, you can fix them with the following query, replacing %TABLENAME% with the actual table name:

optimize table %TABLENAME%

mysql dumping via an ssh tunnel

First , connect to the remote mysql instance via an ssh tunnel on port 10000

ssh -f -N -L 10000:localhost:3306 remoteuser@remoteserver

Try out the connection via the mysql client

mysql -u remote_sql_user --password=remote_sql_pass -h 127.0.0.1 -P 10000 remote_db_name

Type "show databases" , and you should see a list of databases available on the remote sql instance.

To dump out a database locally, quit the mysql client, and type :

mysqldump --host=127.0.0.1 --port=10000 --user=remote_sql_user ==password="remote_sql_pass" --verbose > /your_local_directory/name_of_db.sql


For very large db dumps, it is faster to use zcat & gzip, then pipe to mysql :

gzip name_of_db.sql

zcat name_of_db.sql.gz | mysql -u local_sql_user --password=local_sql_pass --database=name_of_db