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Index Condition Pushdown in MySQL 5.6 and MariaDB 5.5 and its performance impact

 | March 12, 2012 |  Posted In: Benchmarks, Insight for DBAs, MySQL

I have been working with Peter in preparation for the talk comparing the optimizer enhancements in MySQL 5.6 and MariaDB 5.5. We are taking a look at and benchmarking optimizer enhancements one by one. So in the same way this blog post is aimed at a new optimizer enhancement Index Condition Pushdown (ICP). Its available […]

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What does Handler_read_rnd mean?

 | June 15, 2010 |  Posted In: Insight for Developers, MySQL

MySQL’s SHOW STATUS command has two counters that are often confusing and result in “what does that mean?” questions: Handler_read_rnd Handler_read_rnd_next As I understand it, there is some historical context to the choice of names here, hearkening back to before I was involved with MySQL, way back when it was a wrapper around ISAM tables […]

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A workaround for the performance problems of TEMPTABLE views

 | May 19, 2010 |  Posted In: Insight for Developers, MySQL

MySQL supports two different algorithms for views: the MERGE algorithm and the TEMPTABLE algorithm. These two algorithms differ greatly. A view which uses the MERGE algorithm can merge filter conditions into the view query itself. This has significant performance advantages over TEMPTABLE views. A view which uses the TEMPTABLE algorithm will have to compute the […]

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Joining on range? Wrong!

 | May 17, 2010 |  Posted In: Insight for Developers, MySQL

The problem I am going to describe is likely to be around since the very beginning of MySQL, however unless you carefully analyse and profile your queries, it might easily go unnoticed. I used it as one of the examples in our talk given at phpDay.it conference last week to demonstrate some pitfalls one may […]

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When the subselect runs faster

 | March 18, 2010 |  Posted In: Insight for Developers, MySQL

A few weeks ago, we had a query optimization request from one of our customer. The query was very simple like:

This column in the table is looks like this:

The table have 549252 rows and of course, there is an index on the col1. MySQL estimated the cardinality of that index as […]

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