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Search Results for: lock_time

A TokuDB Stall Caused by Conflicting Transactions When Opening a Table

One of our customers reported that ‘create table select from’ statements stall for a period of time equal to the TokuDB lock timeout.  This indicated a lock conflict between multiple transactions.  In addition, other MySQL …


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 …


How to find MySQL queries worth optimizing ?

One question I often get is how one can find out queries which should be optimized. By looking at pt-query-digest report it is easy to find slow queries or queries which cause the large portion …


Hidden columns of query_review_history table

You can use pt-query-digest to process a MySQL slow query log and store historical values for review trend analysis into query_review_history table. According to its official documentation you can populate many columns in that table …


Identifying the load with the help of pt-query-digest and Percona Server

Overview Profiling, analyzing and then fixing queries is likely the most oft-repeated part of a job of a DBA and one that keeps evolving, as new features are added to the application new queries pop …


When Does InnoDB Update Table Statistics? (And When It Can Bite)

An InnoDB table statistics is used for JOIN optimizations and helping the MySQL optimizer choose the appropriate index for a query. If a table’s statistics or index cardinality becomes outdated, you might see queries which …


Ultimate MySQL variable and status reference list

I am constantly referring to the amazing MySQL manual, especially the option and variable reference table. But just as frequently, I want to look up blog posts on variables, or look for content in the …


Is your server’s performance about to degrade?

I’ve been talking and writing a bit lately about the scaling problems I’m seeing on fast servers running lots of queries. As a rough guide, I’m seeing this in servers running 20k queries per second …


InnoDB: look after fragmentation

One problem made me puzzled for couple hours, but it was really interesting to figure out what’s going on. So let me introduce problem at first. The table is

Table has 11864696 rows and …


Profiling MySQL stored routines

These days I’m working with a customer who has an application based entirely on stored routines on MySQL side. Even though I haven’t worked much with stored procedures, I though it’s going to be a …