Post: Hijacking Innodb Foreign Keys
…a table rebuild. In some real life production cases you might find tables…row in set (0.00 sec) mysql> create table parentx(i int) engine=innodb; ERROR 1005 (HY000): Can’t create table…The post...
View ArticlePost: The Optimization That (Often) Isn't: Index Merge Intersection
…MySQL could only use one index per table in a…how the server should be finding and manipulating data, they can be quite effective. In…rows: 32404 Extra: Using where 1 row in set (0.00 sec) Making this...
View ArticlePost: Recovering Innodb table Corruption
…rows and it was too little while skipping 80 rows was OK. Again using binary search you can find out how many rows…The post Post: Recovering Innodb table Corruption appeared first on MySQL Performance...
View ArticlePost: Troubleshooting MySQL Memory Usage
…how it uses MySQL to identify potential causes. Is it working with large blobs ? Using user variables ? Prepared Statements ? memory tables ? In a…how many user variables are allocated (and how much...
View ArticlePost: MySQL 5.6 vs MySQL 5.5 and the Star Schema Benchmark
… findings here. Just a few notes: I tested two scenarios: a …in 587MB of raw data, mostly in one table (lineorder). Each of the 13 queries were executed serially in a…rows in set (0.00 sec) After...
View ArticlePost: MySQL Slow query log in the table
…MySQL 5.1 get MySQL slow query log logged in mysql.slow_log table instead of the file as you had in…table format for slow_log is CSV with no indexes typical operations like finding how many queries...
View ArticlePost: Data compression in InnoDB for text and blob fields
…in a table while leaving other columns uncompressed? While working on a customer case this week I saw an interesting problem where a table had many…MySQL 5.5) you can now leverage table compression by...
View ArticlePost: MySQL EXPLAIN limits and errors.
…how many rows will be examined MySQL will still print full number. Here is example: mysql> explain select * from lt limit 10; +—-+————-+——-+——-+—————+———+———+——+——+————-+ | id | select_type |...
View ArticlePost: How to find MySQL queries worth optimizing ?
…rows in set (0.00 sec) In this case we actually join 2 tables but because the access type to the tables is “const” MySQL…how many rows query sends after group by, distinct and aggregate functions are...
View ArticlePost: MySQL Query Patterns, Optimized - Webinar questions followup
…many…a random value, look up the row with “=” instead of “>” and be guaranteed to find…rows in the `kind_type` table to be first, then look up matching rows in `title` by a…in this case to force...
View ArticlePost: Schema changes - what's new in MySQL 5.6?
…rows in set (0.01 sec) What you see above is how changing table‘s structure works in MySQL in…many possible scenarios! OVERHEAD The fact that a table is ready for writes during Online DDL in…The post...
View ArticleFull Text Search Webinar Questions Followup
I presented a webinar this week to give an overview of several Full Text Search solutions and compare their performance. Even if you missed the webinar, you can register for it, and you’ll be emailed...
View ArticleDifferences between READ-COMMITTED and REPEATABLE-READ transaction isolation...
As an instructor with Percona I’m sometimes asked about the differences between the READ COMMITTED and REPEATABLE READ transaction isolation levels. There are a few differences between READ-COMMITTED...
View ArticleInnoDB Full-text Search in MySQL 5.6 (part 1)
I’ve never been a very big fan of MyISAM; I would argue that in most situations, any possible advantages to using MyISAM are far outweighed by the potential disadvantages and the strengths of InnoDB....
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Understanding the maximum number of columns in a MySQL table
This post was initially going to be two sets of polls: “What is the maximum number of columns in MySQL?” and “What is the minimum maximum number of columns in MySQL?”. Before you read on, ponder those...
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The small improvements of MySQL 5.6: Duplicate Index Detection
Here at the MySQL Performance Blog, we’ve been discussing the several new features that MySQL 5.6 brought: GTID-based replication, InnoDB Fulltext, Memcached integration, a more complete performance...
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Using the new spatial functions in MySQL 5.6 for geo-enabled applications
Geo-enabled (or location enabled) applications are very common nowadays and many of them use MySQL. The common tasks for such applications are:Find all points of interests (i.e. coffee shops) around...
View Articleinnodb_stats_on_metadata and slow queries on INFORMATION_SCHEMA
INFORMATION_SCHEMA is usually the place to go when you want to get facts about a system (how many tables do we have? what are the 10 largest tables? What is data size and index size for table t?, etc)....
View Article2 cases for MySQL server overload
Your MySQL server is overloaded. You see hundreds of running queries in the SHOW PROCESSLIST taking many seconds to run, or can’t connect at all because all connections slots are busy. If you have...
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Analyzing WordPress MySQL queries with Query Analytics
This blog, MySQLPerformanceBlog.com, is powered by WordPress, but we never really looked into what kind of queries to MySQL are used by WordPress. So for couple months we ran a Query Analytics (part of...
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