EXPLAIN EXTENDED can tell you all kinds of interesting things

While many people are familiar with the MySQL EXPLAIN command, fewer people are familiar with “extended explain” which was added in MySQL 4.1 EXPLAIN EXTENDED can show you what the MySQL optimizer does to your query. You might not know this, but MySQL can dramatically change your query before it actually executes it. This process […]

A workaround for the performance problems of TEMPTABLE views

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 […]

Debugging problems with row based replication

MySQL 5.1 introduces row based binary logging. In fact, the default binary logging format in GA versions of MySQL 5.1 is ‘MIXED’ STATEMENT*;   The binlog_format  variable can still be changed per sessions which means it is possible that some of your binary log entries will be written in a row-based fashion instead of the […]

fadvise – may be not what you expect

I often hear suggestion to use

system call to avoid caching in OS cache. We recently made patch for

, which supposes to create archive without polluting OS cache, as like in case with backup, you do not really expect any benefits from caching. However working on the patch, I noticed, that

with […]

Getting around optimizer limitations with an IN() list

There was a discussion on LinkedIn one month ago that caught my eye: Database search by “within x number of miles” radius? Anyone out there created a zipcode database and created a “search within x numer of miles” function ? Thankful for any tips you can throw my way.. J A few people commented that […]

Tokyo Tyrant -The Extras Part III : Write Bottleneck

This is part 3 of my Tyrant extra’s, part 1 focused on durability, part 2 focused on the perceived performance wall. #3.  Tokyo Cabinet Can have only a single writer thread, bottlenecking performance When writing an application using Tokyo Cabinet only one connection can be opened as a “writer”  while the rest are readers.  Tyrant […]