Search Results for: covered query

Advanced MySQL Query Tuning: Webinar followup Q&A

Thanks to all who attended my “MySQL Query Tuning” webinar on July 24.  If you missed it, you can you can download the slides and also watch the recorded video. Thank you for the excellent questions after the webinar as well. Query tuning is a big topic and, due to the limited time, I had […]

MySQL Webinar: Advanced Query Tuning

On July 24 at 10 a.m. PDT, I will be delivering a Webinar on Advanced MySQL Query Tuning. I will focus on optimizing the common slow queries with group by and order by. Those queries usually create temporary tables and perform a “filesort” operation. I will show how to optimize those queries so that they […]

MySQL Query Patterns, Optimized – Webinar questions followup

On Friday I gave a presentation on “MySQL Query Patterns, Optimized” for Percona MySQL Webinars.  If you missed it, you can still register to view the recording and my slides. Thanks to everyone who attended, and especially to folks who asked the great questions.  I answered as many as we had time for  during the session, but here […]

Analyzing Slow Query Table in MySQL 5.6

Next week I’m teaching an online Percona Training class, called Analyzing SQL Queries with Percona Toolkit.  This is a guided tour of best practices for pt-query-digest, the best tool for evaluating where your database response time is being spent. This month we saw the GA release of MySQL 5.6, and I wanted to check if any […]

Query_cache and column level privileges

Recently we were puzzled by question how query_cache works with column level privileges. The question was appeared as we discovered function query_cache_send_result_to_client is called before real parsing of query, so at the moment of execution the query_cache is not able to know which columns are accessed. Looking into source code I found out that in […]

Duplicate indexes and redundant indexes

About every second application I look at has some tables which have redundant or duplicate indexes so its the time to speak about these a bit. So what is duplicate index ? This is when table has multiple indexes defined on the same columns. Sometimes it is indexes with different names, sometimes it is different […]