On Tue, Mar 16, 2010 at 12:16 PM, Rehan Iftikhar <[email protected]> wrote: > Tom > > Thanks for the great summary! I found the MySQL Differences page on the > Drizzle wiki and I was pleasantly surprised how technical and thorough it > is. It should serve as a suitable bridge between Sasha Pachev's book and the > current (future) state of Drizzle.
Indeed, Tom, that was an excellent summary! Thanks! Rehan, if you have questions, feel free to join us on Freenode IRC #drizzle. We're always available for questions :) Cheers! Jay > I will try and keep a log (wiki?) of notes while reading Sasha's book and > groking the MySQL/Drizzle source and post the link on the Drizzle Wiki. > > On Mon, Mar 15, 2010 at 10:25 PM, Tom Hanlon <[email protected]> > wrote: >> >> Rehan, >> >> On 16 Mar 2010, at 00:15, Rehan Iftikhar wrote: >> >>> Hi >>> >>> I was wondering how relevant the content in Understanding MySQL Internals >>> (http://www.amazon.com/Understanding-MySQL-Internals-Sasha-Pachev/dp/0596009577) >>> is to drizzle? >>> >> >> >> Sasha Pachev's book on mySQL internals would be significantly more >> relevant to Drizzle than a book on Oracle internals. >> >> The Core Drizzzle team are likely going to clam that the two are very >> different, but they have spent the last year making it different, and >> working on the differences. So the similarities might be somewhat invisible >> to them. So I will take a shot at an overview and they can correct me as >> needed. >> >> I would say that until the Drizzle internals book is written that book >> would be the closest. I think most would agree that the differences are >> significant, but still the core of drizzle is a derived work from MySQL. In >> addition the storage engine concept and compatibility with the major MySQL >> storage engines such as innodb is in drizzle as well. >> >> I can not find my copy of Sasha Pachev's book or I would go through it and >> tell you how well it covers the concepts that are similar. >> >> The Drizzle team can add some details but as far as I can tell here are >> some things that are different and some things that are the same. >> >> Authentication: >> Drizzle is plugin based PAM and http_auth and others. >> MySQL built in authentication of user,host, password at the DB, >> table and column level. Stored in a database table >> >> Thread management: >> I assume that this is similar. MySQL until very recently had a >> single multi threaded process. A thread was allocated per connection. That >> thread might be cached when the user disconnected and re-used for an >> incoming connection. In recent versions a "pool of threads" optimization has >> been added where a pool of threads is allocated for user connections and >> those threads are used as needed. I am not sure what code base drizzle >> started with and how stable pool of threads was anyhow, so what drizzle >> uses.. I do not know. >> >> Parser: >> I have not heard much chatter about the drizzle parser so I assume >> it is derived from the MySQL parser. I imagine MySQL dual license model >> caused the MySQL parser to not reuse some open source parser libraries so >> perhaps the code has been cleaned up.. but I am only guessing. >> >> Optimizer: >> I have not heard much chatter here either, so I assume that the >> optimizer is derived from the MySQL optimizer as well. The drizzle team can >> correct me if I am wrong. >> >> Replication: >> MySQL relied upon what had been a statement based binary log. >> Meaning that if a statement might have changed data, it was written to a log >> file at the SQL layer and the slave would replay the statements. Features >> were added in MySQL 5.1 to instead of logging the statements that may have >> changed or added rows we instead ask the storage engine for copies of the >> changes and place those in a "row" based replication log the binary log. >> Statement based was still supported and it was/is messy. Statement based had >> some issues, but row based added some issues and some confusion and some >> bugs. >> Drizzle, tore all of that out and implemented replication >> capability based upon google protocol buffers. >> http://code.google.com/apis/protocolbuffers/docs/overview.html Jay covers >> the internals fairly well in a series of blog posts >> here..http://www.joinfu.com/2009/10/drizzle-replication-changes-in-api-to-support-group-commit/ >> >> It is fair to say that there are significant differences between >> the two systems regarding replication. >> >> Transaction stuff: >> mySQL at the core was not a transactional database, it was made to >> work somehow with transactional storage engines. I sometimes would think of >> the MySQL server or the SQL layer as coordinating a group transaction to the >> underlying storage engines. The relationship was complicated, and it >> complicated replication somewhat in ways that are a little complicated to go >> into, but in a purely transactional system the same log and system that is >> used for transactional consistency and durability can typical be used to >> assist the replication process. I am not sure what Drizzles statement of >> intent regarding transactions is. But it is important to note that the MySQL >> way.. led to a somewhat messy implementation and it seems that Drizzle is >> hard at work even lately in terms of cleaning that up. >> >> It seems that any Database that allows plugins for Storage engines >> is going to have to hand off the Durability Requirements to the storage >> engines so in a rough outline things are somewhat similar, but the >> differences will be many. >> >> I could picture Drizzle be more transactional and still allowing the >> storage engines to ignore the transactional stuff. Whereas MySQL was not >> transaction and forced the storage engines to do extra work in order to be >> transactional. >> >> If you are looking for an understanding of the Relational Model and how >> SQL is optimized and how Joins are performed, I found Dan Tow's book SQL >> tuning http://www.amazon.com/SQL-Tuning-Dan-Tow/dp/0596005733 to be helpful. >> It goes through the concepts of indexes and joins really well. >> >> If I find my copy of Sasha Paschev's book I can give you a better review. >> >> >> >> -- >> Tom Hanlon >> >> >> >> >> >> >> >> >>> -- >>> -Rehan >>> _______________________________________________ >>> Mailing list: https://launchpad.net/~drizzle-discuss >>> Post to : [email protected] >>> Unsubscribe : https://launchpad.net/~drizzle-discuss >>> More help : https://help.launchpad.net/ListHelp >> > > > > -- > -Rehan > > _______________________________________________ > Mailing list: https://launchpad.net/~drizzle-discuss > Post to : [email protected] > Unsubscribe : https://launchpad.net/~drizzle-discuss > More help : https://help.launchpad.net/ListHelp > > _______________________________________________ Mailing list: https://launchpad.net/~drizzle-discuss Post to : [email protected] Unsubscribe : https://launchpad.net/~drizzle-discuss More help : https://help.launchpad.net/ListHelp
