Personally, I recent the statement; 'Considering MySQL has proven itself time and time again in terms of reliability, licencing flexibility and performance, such statements are baseless regardless of what arguments you make for which features'; based on experience, mysql proved that it was not reliable, tho performance was top of the line.
In my opinion, if you're concerned with reliability, mysql should not be an option. I had daily table corruptions, and thus one of my main tasks was to run mysql repair jobs regularly, just to keep everything running. Granted, postgresql has it's own problems, mainly with performance and lack of a proper master / slave replication model, but that's a small price to pay for reliability. Just my $0.02 worth. Regards, John Hansen -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Chris Nolan Sent: Sunday, February 15, 2004 4:42 PM To: dbmail-dev@dbmail.org Subject: Re: [Dbmail-dev] some speed tests Dear Aaron, My comments are also inline. :-) On Sun, 2004-02-15 at 12:27, Aaron Stone wrote: > Comments inline... > > Chris Nolan <[EMAIL PROTECTED]> said: > > > Forgive the bluntness of the statement, but why is anyone even > > worrying > > about transactions as they relate to MySQL??? > > Because we are currently structured to have a single set of mid-level > database operations that are translated into specific low-level > database function calls. The upside is that there isn't any database > specific handling outside of these mid-level functions. The downside > is that we need to make sure that function calls for certain features > are consistent with analogous features in each database and that they > carry with them enough information to make the appropriate low-level > call. A good example is the last inserted id number. In MySQL, you > only need the database connection identifier to get this. In > PostgreSQL, yo need both the database connection and the table > identifier. For DBMail to have a mid-level function that worked for > both, we'd have to make sure that it took both arguments and used them > as needed for whichever database's low-level calls were being used. > (Those were off the top of my head, so they may be incorrect, but they > do illustrate my point.) I've looked through the DBMail source code on a few occassions and even released a dodgy tool to convert Cyrus mailboxes to DBMail a while ago. The fact that I can use the calls present in the DB modules and avoid having to write queries by hand for each different DB is an excellent feature of the DBMail API. I have nothing negative to say here at all. > > > COMMIT in MySQL is passed to the table handler. In the case of > > MyISAM > > tables, the handler disregards the statement. For InnoDB and BDB tables, > > COMMIT acts as it does in PostgreSQL. > > So then we have THREE different configurations to consider, and need > to be sure to design the mid-level interface appropriately. My statement was meant to say that the MyISAM table handler will just disregard BEGIN and COMMIT statements, just as it parses but ignores CHECK and FOREIGN KEY constraints in table creation, thus illustrating that you wouldn't need to add a mysql-with-transactions directory to the source tree. > > > So various people in this thread implying that MySQL isn't really a > > database need to do some more reading. > > If you're referring to my suggestion that the transaction functions > are a noop for MySQL, then you're reading too deeply... I just didn't > realize that InnoDB would handle transactions entirely normally. My apologies, I was not referring to you at all! Yourself and your collegues have provided the world with a very, very funky mail repository! I was referring to someone who said in the body of their message posted to another branch of this thread "the supposed database mysql". Considering MySQL has proven itself time and time again in terms of reliability, licencing flexibility and performance, such statements are baseless regardless of what arguments you make for which features. For example, Visual FoxPro's backend is technically a database but provides nothing in the way of a privilege system (you need write access to record locking, so filesystem-level controls are no good either). > > > In summary, just encapsulate everything in transaction blocks and > > the > > underlaying database will act appropriately. > > Right. That's what we're talking about. > > Is the entire point of your comment that we can safely use > > BEGIN; > > .. whatever dbmail does... > > COMMIT; > > regardless of whether or not we know if the host database actually > supports these keywords? You could have just said that. I could have, but then I would have risked putting an end to the thread. :-) Please accept my apology - I never meant to offend yourself or anyone else who contributes to DBMail. It seems my reading of the post I mentioned above caused me to be a bit heavier than I should have been. But yes, you have perfectly summarised the point of my comment. > > > Regards, > > > > Chris > > > > Aaron Stone wrote: > > > > >I don't even know where to begin in terms of designing the delivery > > >chain around transactions. Could we do it as simply as adding > > >functions... > > > > > > void db_begin_transaction(void); > > > void db_flush_transaction(void); (or db_commit_...?) > > > > > >and then calling these functions before and after each major > > >section of database code? For the delivery chain, we could do it > > >inside of insert_message(). For dbmail-smtp, this basically means > > >that the execution of the whole program is within one transaction. > > >For dbmail-lmtpd, it means that each message is delivered within a > > >transaction but the miscellaneous queries before the main message > > >delivery chain are not transacted. For MySQL, these functions would > > >be noops. > > > > > >Thing that might work? > > > > > >Aaron > > > > > > > > >Thomas Mueller <[EMAIL PROTECTED]> said: > > > > > > > > > > > >>Hi Aaron, > > >> > > >> > > >> > > >>>Do you have any way of narrowing this down to specific queries > > >>>that are taking the longest and/or are being executed the most? > > >>>That would identify which low-level database functions are being > > >>>called, then we can just trace our way up the call chain to see > > >>>who's misbehaving or acting on a flawed design. Also, if you > > >>>could run similar tests against the latest 1.2, it would help to > > >>>give a frame of reference, particularly for my delivery chain > > >>>design. > > >>> > > >>> > > >>That's simple: the main design flaw (actually that's no design > > >>flaw I think, that's because the so called database MySQL couldn't > > >>do transactions in the past) is that dbmail doesn't use > > >>transaction. > > >> > > >>Because of that AutoCommit is used and whenever dbmail does > > >>anySqlQuery Postgres does 'BEGIN; anySqlQuery; COMMIT;' - and that > > >>is terribly slow. To ensure the Durability in ACID the database > > >>has to fflush() every transaction to stable storage! That's why > > >>there is only one solution: we have to use transaction. > > >> > > >>With transactions we could remove the integrity checks of > > >>dbmail-maintenance too, because the database guarantees integrity. > > >> > > >>Anyway, I did a trace of all SQL queries when a mail is copied > > >>using IMAP. I got 35 SELECT, 4 INSERT, 5 UPDATE (44 db operations > > >>to insert one mail?). > > >> > > >>When searching for the sequential scan I found something quite > > >>interesting in the docs: the planer decides for every scan if a > > >>seqScan is cheaper that an index scan, and does a seqScan even if > > >>an index > > >>exists: > > >> > > >>dbmail=> explain SELECT mailbox_idnr FROM mailboxes WHERE owner_idnr=2; > > >> QUERY PLAN > > >>--------------------------------------------------------- > > >> Seq Scan on mailboxes (cost=0.00..1.06 rows=3 width=8) > > >> Filter: (owner_idnr = 2) > > >>(2 rows) > > >> > > >>The table has an index on owner_idnr. > > >> > > >>So I should repeat this test with a database with several hundred > > >>to thousand user, several dozen mailboxes for each user and > > >>several dozen mails in each mailbox to find out if all required > > >>indizes are there. Did anyone write a script to create such a > > >>database? > > >> > > >>But I found a strange query: > > >>SELECT mailbox_idnr FROM mailboxes WHERE mailbox_idnr = '4' AND > > >>owner_idnr = '2' mailbox_idnr is the primary key so that could be > > >>optimized to: SELECT 4 > > >>;-) > > >> > > >> > > >>I don't have a 1.2 installation, I'm sorry. > > >> > > >> > > >>-- > > >>MfG Thomas Mueller - http://www.tmueller.com for pgp key (95702B3B) > > >>_______________________________________________ > > >>Dbmail-dev mailing list > > >>Dbmail-dev@dbmail.org > > >>http://twister.fastxs.net/mailman/listinfo/dbmail-dev > > >> > > >> > > >> > > > > > > > > > > > > > > > > > > > > > _______________________________________________ > > Dbmail-dev mailing list > > Dbmail-dev@dbmail.org > > http://twister.fastxs.net/mailman/listinfo/dbmail-dev > > > > _______________________________________________ Dbmail-dev mailing list Dbmail-dev@dbmail.org http://twister.fastxs.net/mailman/listinfo/dbmail-dev
