mysql denormalization with triggers, specific advice - mysql

Question

I'm considering adding some denormalized information in my database by adding one denormalized table fed by many (~8) normalized tables, specifically for improving select query times of a core use case on my site.
The problems with the current method of querying are:
Slow query times, there are between 8 and 12 joins (some of the left joins) to access the information for this Use Case this can take ~ 3000ms for some queries.
Table Locking / Blocking, When information is updated during busy times of the day or week, (because I'm using MyIsam tables) queries are locked / blocked and this can cause further issues (connections running out, worse performance)
I'm using Hibernate (3.5.2), Mysql 5.0 (all MyIsam tables) and Java 1.6
I'd like some specific suggestions (preferrably based on concrete experience) about exactly what would be the best way to update the the denormalized table.
The following come to my mind
Create a denormalized table with the InnoDb type so that I get row level locking rather than table locking
Create triggers on the properly normalized tables that update the denormalized table,
I'm looking for:
Gotchas - things that I may not be thinking about that will affect my desired result.
Specific MySql settings that may improve performance, reduce locking / blocking on the denormalized table.
Best approaches to writing the Triggers for this scenario.
?
Let me know if there is any other information needed to help answer this question.
Cheers.

Answer 1

I've now implemented this, so I thought I'd share what I did, I asked a mate who's a dba (Greg) for a few tips and his answers basically drove my implementation:
Anyway like "Catcall" implied using TRIGGERS (in my case at least) probably wasn't the best solution. Greg suggested creating two denormalized tables with the same schema, then creating a VIEW that would alternate between the two denormalised tables one being "active" and the other being "deactive" the active table would be the one that was being actively queried by my web application and the deactive table could be updated with the denormalised information.
My application would run queries against the VIEW whose name would stay the same.
That's the crux of it.
Some implementation details (mysql 5.0.n):
I used stored procedures to update the information and then switch the View from denorm_table_a to denorm_table_b.
Needed to update the permissions for my database user
GRANT CREATE, CREATE VIEW, EXECUTE, CREATE ROUTINE, ALTER ROUTINE, DROP, INSERT, DELETE, UPDATE, ALTER, SELECT, INDEX on dbname.* TO 'dbuser'#'%';
For creating a copy of a table the: CREATE TABLE ... LIKE ....; command is really useful (it also copies the index definitions as well)
Creating the VIEW was simple
CREATE OR REPLACE VIEW denorm_table AS SELECT * FROM denorm_table_a;
CREATE OR REPLACE VIEW denorm_table AS SELECT * FROM denorm_table_b;
I created a special "Denormalised Query" Object in my middle tier which then mapped (through hibernate) to the denormalised table (or View in fact) and allowed easy and flexible querying throught Hibernate Criteria mechanism.
Anyway hope that helps someone if anyone needs any more details let me know,
Cheers
Simon

Answer 2

Here is I solution that I used to denormalize a mysql one-to-many relation using a stored procedure and triggers:
https://github.com/martintaleski/mysql-denormalization
It explains a simple blog article to article image relation, you will need to change the fields the fields and queries to apply it to your scenario.