> -----Original Message----- > From: Devananda [mailto:[EMAIL PROTECTED] > Sent: Thursday, September 22, 2005 19:03 > To: Jeff > Cc: mysql@lists.mysql.com > Subject: Re: MyISAM to InnoDB > > > Jeff wrote: > >>-----Original Message----- > >>From: Devananda [mailto:[EMAIL PROTECTED] > >>Sent: Thursday, September 22, 2005 16:14 > >>To: Jeff > >>Cc: mysql@lists.mysql.com > >>Subject: Re: MyISAM to InnoDB > >> > >> > >>Jeff wrote: > >> > >>>True, is there a way to tell a slave to not replicate > >> > >>certain queries > >> > >>>like alter table or would I need to get creative and stop > >> > >>replication > >> > >>>and all writes to the main database, then issue the alter table > >>>statement, then restart replication with a set global > >>>slave_sql_skip_counter=1 so that it skips the alter statemtent? > >> > >>There's a much easier way - issue the statement "SET > >>SQL_LOG_BIN = 0;" > >>before issuing any ALTER TABLE statements. This will cause all > >>statements for the duration of that session to not be > written to the > >>binlog. See http://dev.mysql.com/doc/mysql/en/set-option.html > >>for more > >>information. > >> > > > > > > First off, thanks for the help to you and Bruce both! > > > You're quite welcome, Jeff :) > > > When you say here, "for the duration of that session" does > that mean > > that only queries I issue with my connection skip the > binlog? Or do > > all queries during that time skip the binlog. In other > words, when I > > SET SQL_LOG_BIN = 0; should I first stop all applications > writing to > > the database to prevent missing data in the slaves? > > > > > It only affects that connection. Bruce wrote a response at about the > same time I did; his covers this topic as well. SQL_LOG_BIN > is a session > variable, meaning that it only affects the current session > (connection). > So, any applications running at the same time will not be > affected by a > change to this variable, and if you close your client and > reconnect, you > will have to set the variable again. As Bruce suggested, it's best to > set it only when you need it and unset it immediately > afterwards (as a > precaution against operator error, not because it affects the server). > > I do want to point out that while the commands you issue > (after setting > SQL_LOG_BIN to 0) will not be written to the binlog (thus > will not run > on any slave reading from this server), they may affect other running > processes on the server. If, for example, you run an ALTER TABLE on a > table currently in MyISAM format, the table will be locked and all > processes running on that server that read from / write to that table > will wait until that ALTER finishes. Setting SQL_LOG_BIN to 0 doesn't > affect this in any way - it _only_ affects whether statements > from that > specific session are recorded in the binary log. >
Thanks, that answer my question regarding SQL_LOG_BIN varialbe. > Side question - you've stated that you are planning to migrate to > InnoDB, but you haven't said anything to the list about how much data > you have. Just be aware that it can take a lot of time and disk space > for MySQL to transfer all your data from one format to the other (of > course depending on how much data you have) and if anything > goes wrong > during that time, the results will probably not be what you > expect, or > want. I would advise you to at least investigate an alternate > approach > if you have a lot of data - take the server you are going to > migrate out > of the 'cluster' and make sure it is not processing any data / no > clients are connecting to it; dump all your data to text files, > preferably separating your data definition statements (ie > CREATE TABLE > statements) from your actual data; modify the CREATE statements to > specify the InnoDB engine; lastly load all the data from the > text files > into MySQL, and bring this server back into the 'cluster'. > > If you don't have a _lot_ of data, then it may not be worth all that > work. Of course, "a lot" is subjective; I'd say, based purely > on my own > experiences with this, that if you are going to migrate 1G of > data, you > will probably be better off exporting / alter the text files / > importing. If you have 10's or 100's of G of data, I would strongly > recommend that you do it this way. And regardless of how much > data you > have, it is, IMHO, safer to export/import. Well like you say a "lot" of data is subjective. Our situation is this; we currently have a DB01 up and running and in production. We're moving to a more redundant data center and have purchased new hardware to migrate the database to (new server will be DB03). The speed of the database directly affects our profitability. This being the case I've suggested to our developers that we take the opertunity to migrate the tables involved in heavy write actions from MyISAM to InnoDB on the new DB03 server before we put it into production. Currently I have DB03 up and running (all MyISAM) at the new datacenter and doing circular replication with DB01 over VPN. No apps or users are currently writing or even reading from DB03 yet. Even if we migrate selected tables in DB03 to InnoDB I'd like to keep the downstream (one way) replicated servers using MyISAM as most of the activity on those is read only. As for the size of the tables in question, they are currently; 2gig Table1.MYD 200M Table1.MYI 14k Table1.frm 422k Table2.MYD 114k Table2.MYI 11k Table2.frm Our lead developer here has made the statement, "why not just convert the entire db to InnoDB for the sake of simplicity and ease?" As far as I'm concerned, simplicity and ease would be to leave it as is but we're looking to eek out as much speed in our transactions as possible so simplicity, ease and performance don't always go together. If I understand what your suggesting above I should: 1) Stop all writes/read to the table (just replication at this point) 2) Issue a "show create table" statement for Table1 and Table2, save these results and modify the engine type to InnoDB for later use. 3) Dump all data from Table1 and Table2 to text files. 4) Setup the db for InnoDB use (add variables to my.cnf file as needed to support InnoDB). 5) Restart the database (make sure replication doesn't start) 6) Issue a SQL_LOG_BIN=0 7) Drop the old Table1 and Table2 8) Use the previousely created "create table" queries to rebuild Table1 and Table2 in InnoDB 9) Re-import the data from the text files into the new Table1 and Table2 10) Issue a SQL_LOG_BIN=1 11) Restart replication. If you're > interested, I would > be happy to talk more about a method to automate this process > over many > tables / lots of data. > > > Best Regards, > Devananda vdv > I'd be very interested to discuss that. Even if I don't use it in this particular situation, knowledge never hurts! ;o) Thanks! jeff -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
