Hi Peter,
I see that query_lock is supposed to lock the rows that it specifies.
MySQL only supports locks on rows with the InnoDB engine. But as far as I know, when installing the mysql tables with kamdbctl, the tables are added with the MyISAM engine.
So, should I start modifying the install scripts so that we use InnoDB engine, or is a table-lock sufficient when myisam is used? Mysql will not give an error if the engine does not support locking on individual rows. So the experience will be transparent for the end user, except for the locking of the whole table.
Also, it is important that the columns that the query compares against, is indexes, or else the table will be locked even if the table engine is InnoDB. I'm not sure if presence only queries for indexed columns?
Regards,
Håkon