Optimize only fragmented tables in MySQL

When you are using MySQL, you will (likely) have tables that can be fragmented. In MySQL terms this is called "OPTIMIZE".

You could simply OPTIMIZE every table in every database, but during an OPTIMIZE, the tables are locked, so writing is not possible.

To minimize the time that MySQL will be locked (and results cannot be written), here is a script that checks fragmentation of every table of every database. Only if a table is fragmented, the table is OPTIMIZED.


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"

Result will look something like this:

MySQL username: root
MySQL password:
database.cache_filter is 19% fragmented.
meinit.cache_filter optimize status OK
database.cache_page is 35% fragmented.
meinit.cache_page optimize status OK

You may comment out that line with OPTIMIZE TABLE in it, if you are just interested in seeing the fragmentation.

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References Red Hat Certified Architect By Robert de Bock Robert de Bock
Curriculum Vitae By Fred Clausen +31 6 14 39 58 72
By Nelson Manning [email protected]