Thanks Paul, it looks like you are correct. Two 'Kieran Kelleher' email stated:
> There is also no row locking on EO_PK_TABLE with myisam, so you will get > primary key clashes and subsequent failed inserts if the db is sufficiently > contended. and > (1) Never use MyISAM - no transactional support means a failed > editingContext.saveChanges() will not result in a rollback and semi-saved > changes to the database..... data integrity goes out the window. Use InnoDB > .... don't just convert live DB though, dump/import to a standby server, > configure InnoDB first completely and actually do a little bit of studying > the MySQL docs to understand how. Also, get a head start here: > https://github.com/kierankelleher/gic-mysql-tools > > (2) Don't create "real" foreign key constraints because MySQL does not > support deferred constraints (which is the biggest negative of using MySQL). > Instead just manually create indexes on every foreign key field. Otherwise > your performance will deteriorate as tables sizes get larger. Seems like sound advise. I now have some careful un-picking to do. Also, incase anyone is interested, I eventually found the primary key generation code in JDBCPlugIn.class : newPrimaryKeys(int count, EOEntity entity, JDBCChannel channel) Other DB plugins do their own thing, but the MySQL one appears to fall back on JDBCPlugIn. Thanks again, Mark On 17 May 2013, at 21:18, Paul Yu wrote: > Well you certainly should not use MyIsam system. Innodb is the right answer. > See Kieran's post on this subject. > > But I'm not sure that will be the end of your issues. > > Sent from my iPad > > On May 17, 2013, at 4:03 PM, Mark Gowdy <go...@mac.com> wrote: > >> Hi, >> >> We have started getting more of these errors recently, now that the system >> is under more load. >> >> ---- >> EvaluateExpression failed: >> <com.webobjects.jdbcadaptor._MySQLPlugIn$MySQLExpression: "INSERT INTO >> queue_item(ITEM_DATE, ... etc....) >> Duplicate entry '4183884' for key 'PRIMARY' >> ---- >> >> I believe the problem is due to the fact that there is more than one >> instance trying to write to the 'queue_item' table, and the EO_PK_TABLE >> mechanism is handing out the same ID more than once. >> Probably something to do with locking. >> >> Our Database is MySQL 5, and the EO_PK_TABLE is of type MyISAM. >> >> I tried to find the mechanism that allocate the primary key, but I keep >> bumping up against: >> >> EOAdaptorChannel: >> @Deprecated >> public NSDictionary<String, Object> primaryKeyForNewRowWithEntity(EOEntity >> entity){ >> return null; >> } >> >> >> Any advise would be appreciated, >> >> Thanks, >> >> Mark >> >> _______________________________________________ >> Do not post admin requests to the list. They will be ignored. >> Webobjects-dev mailing list (Webobjects-dev@lists.apple.com) >> Help/Unsubscribe/Update your Subscription: >> https://lists.apple.com/mailman/options/webobjects-dev/pyu%40mac.com >> >> This email sent to p...@mac.com
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