1. Generally reducing fragmentation in the data/index files will reduce the footprint of
tables on disk, and can be more efficient to query. With innodb you need to be using the
innodb-file-per-table option, and then you can use OPTIMIZE TABLE table; to rebuild it.
You don't get detailed progress like with myisamchk, but that's not important anyway.
You can estimate how long it will take by keeping track of how long any given ALTER /
OPTIMIZE takes in GB/hr.
2. Don't stare at the screen. Start it, script the process & have it email your
phone when it's done. Do something else in the mean time.
3. Yes, innodb table will take more space on disk. If you have a really long primary
key, and lots of secondary indexes, then it can take a *lot* more. Disk is cheap, don't
worry about it.
From: Hank [mailto:heskin@stripped]
Sent: Tuesday, September 28, 2010 3:29 PM
Subject: Migrating my mindset from MyISAM to InnoDB
Primarily due to many positive posts I've seen about MySQL 5.5 and
advances in InnoDB, I'm seriously considering converting all my MyISAM
databases to InnoDB. I don't need many of the InnoDB features, but
if I'm going to upgrade from 4.1.14 to 5.5, I might as well bit the
bullet since that seems to be the direction of MySQL/Oracle.
I've been using MySQL 4.1.14 for years in my production environment,
including one master and several slaves for report and long running
Every 6 to 12 months the master MYI index files grow fairly large, so
I take the production database offline, and run myisamchk -r on the
index files to rebuild them and shrink them back down again. I usually
get a 20% to 30% space saving and improved performance after the
rebuilds. This has worked very well for me for, well, almost 10 years
And when I say "large" my two main tables have about 200 million rows,
and the myisamchk can take between 60-160 minutes to complete.
I very much like how verbose myisamchk is in detailing which index it
is currently rebuilding, and the progress in terms of records
SO, my questions are this:
1. With InnoDB, do the indexes ever need to be rebuilt to reduce index
size and improve performance like I get with MyISAM?
2. If so, are there any tools like myisamchk to monitor the InnoDB
index rebuild process, other than issuing a "repair table..." and
staring indefinitely at a blank screen until it finishes hours later?
3. I've been testing the rebuild process during upgrading using
"alter table <table_name> engine=innodb" to convert my tables from
4.1.14 to 5.5.6, and I'm seeing a 130% increase (more than double) in
the raw disk space required for the new InnoDB tables compared to
their old MyISAM counterparts. (I am using single-file-per-table). Is
this normal? If not, how can I adjust the space requirements for
these tables so they don't take up so much additional space?
I'm sure I'll have more questions later, but many thanks for your
comments and thoughts.
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