Why opensource?

Start from a specific situation: you are on a tight schedule, with pressure from management to approve or prove an issue on the software release being tested, and the counterpart R&D team blames you that the metrics are wrong. Actually, you check the application and they are right… looking into the source code u see the bug, u fix it, and within hours u are back on the main business, finalizing the testing activity. Now, what would have happened with a proprietary testing tool? You couldn’t have checked the code. You would have had to argue with the ur R&D team about the existence of the issue, and with the vendor on the other side. Project would have been delayed or QA totally skipped, with all the risk it takes having a potentially broken release in production. Is it worth the money of the proprietary tool? I preferred to convince my management to spend in R&D resources in my team, and get a solution we could trust. It has proven to be a good choice

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subqueries do not get cached

WTF???

…the cache is not used for queries of the following types:

* Prepared statements
* Queries that are a subquery of an outer query
* Queries executed within the body of a stored function or trigger

http://dev.mysql.com/doc/refman/5.0/en/query-cache-operation.html

+

For certain cases, a correlated subquery is optimized. For example:

val IN (SELECT key_val FROM tbl_name WHERE correlated_condition)

Otherwise, they are inefficient and likely to be slow. Rewriting the query as a join might improve performance.

http://dev.mysql.com/doc/refman/5.1/en/correlated-subqueries.html

I have 5 nested views… from 1 to 4, I have GROUP BY, ORDER BY, JOIN of the data over themselfs and other amenities… and on a ~2milion rows table, it doesn’t take more than 14 seconds…

the last view… has a subquery… evaluating the data related to the “currently evaluated row”, looking on the same table for values of “the same group”… and it gets DAMN SLOW… cause the “query cache” mechanism of MySQL does not kick in

k, tomorrow morning I go for the rewriting… I’ll create a VIEW about the data I need to be correlated, and I’ll JOIN it… let’s see 🙂