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.
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<https://launchpad.net/%7Edrizzle-discuss> >> Post to : [email protected] >> Unsubscribe : >> https://launchpad.net/~drizzle-discuss<https://launchpad.net/%7Edrizzle-discuss> >> More help : https://help.launchpad.net/ListHelp >> > > -- -Rehan
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