Post: Using flow control functions for performance monitoring queries
…in MySQL Queries as they are often abused used to create queries which are poorly readable as well as can hardly be optimized…often have different performance profile. mysql> select count(*) cnt,...
View ArticlePost: Feature Idea: Finding columns which query needs to access
In query examinations it is often interesting which columns query needs to access to provide result set as it … it has to be done manually – look at SELECT clause, WHERE clause, ORDER BY GROUP BY and…...
View ArticlePost: MySQL: Followup on UNION for query optimization, Query profiling
… in MySQL. IN range allows to optimize lookups on the second key part, while BETWEEN and other ranges do not. Using same access type in… happens during query execution – very helpful for MySQL...
View ArticlePost: Shard-Query EC2 images available
… difference In general, a column store performs about 8x-10x better than a row store for queries which access… to use are shown in the EC2 console. That the “private ip” field is selected in the list...
View ArticlePost: Distributed Set Processing with Shard-Query
… need to make some minor abstraction modifications in the data access layer. Shard-Query can provide query execution plans based on the relational algebra… projections were selected for a UNIQUE CHECK...
View ArticlePost: Flexviews - part 3 - improving query performance using materialized views
… a table with CREATE TABLE .. AS SELECT. In fact, this is actually part of …access the orders, order_lines and customers tables directly (the tables on which dashboard_customer_sales is built), then...
View ArticlePost: Join Optimizations in MySQL 5.6 and MariaDB 5.5
…6 config: optimizer_switch=’index_condition_pushdown=off’ optimizer_switch=’mrr=on’ optimizer_switch=’mrr_cost_based=off’ optimizer_switch=’batched_key_access=on’ … optimizer switches and variables in...
View ArticlePost: Multi Range Read (MRR) in MySQL 5.6 and MariaDB 5.5
…in query times between MySQL 5.5 and MySQL 5.6/MariaDB 5.5 This is another area of improvement in the optimizer, as it is clearly a part of the optimizer‘s job to select the best query…The post Post:...
View ArticlePost: MySQL 5.6: Improvements in the Nutshell
…Optimizations – More efficient Optimizer Replication – Optimized… Configuration – - Table Access instrumentation – - …Selection in queries – Full Text Search index for Innodb – Microsecond TIME...
View ArticlePost: MySQL Query Patterns, Optimized - Webinar questions followup
…query in a suboptimal form. Q: Doesn’t the primary key solution for random selection…accesses these first, by looking up the keywords you specify. It doesn’t matter what order you specify the...
View ArticlePost: Schema changes - what's new in MySQL 5.6?
…in MySQL 5.6 is that during the ALTER operation a table being changed can still be fully accessible…Query OK, 1 row affected (0.01 sec) Session1> select max(rev_id) from revision; +————-+ |...
View ArticlePost: InnoDB Full-text Search in MySQL 5.6: Part 3, Performance
...Query Performance Recall the queries that were used in the previous post from this series: 1. SELECT...read/write access) are being exercised here, but I am quite surprised by queries #3 ... | init...
View ArticlePost: Schema Design in MongoDB vs Schema Design in MySQL
…| Michael | | 4 | Cinderella | +—-+————+ mysql> select * from passports; …in…access pattern of the application. This should not be neglected as creating a wrong schema design is a recipe for...
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SQL Injection Questions Followup
I presented a webinar today about SQL Injection, to try to clear up some of the misconceptions that many other blogs and articles have about this security risk. You can register for the webinar even...
View ArticleMySQL Indexing Best Practices: Webinar Questions Followup
I had a lot of questions on my MySQL Indexing: Best Practices Webinar (both recording and slides are available now) We had lots of questions. I did not have time to answer some and others are better...
View ArticleHow 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 of the...
View ArticleTools and Techniques for Index Design Webinar Questions Followup
I presented a webinar this week to give an overview of Tools and Techniques for Index Design. Even if you missed the webinar, you can register for it, and you’ll be emailed a link to the recording.I’d...
View ArticleFull table scan vs full index scan performance
Earlier this week, Cédric blogged about how easy we can get confused between a covering index and a full index scan in the EXPLAIN output. While a covering index (seen with EXPLAIN as Extra: Using...
View ArticleMySQL 5.5 and MySQL 5.6 default variable values differences
As the part of analyzing surprising MySQL 5.5 vs MySQL 5.6 performance results I’ve been looking at changes to default variable values. To do that I’ve loaded the values from MySQL 5.5.30 and MySQL...
View ArticleMySQL optimizer: ANALYZE TABLE and Waiting for table flush
The MySQL optimizer makes the decision of what execution plan to use based on the information provided by the storage engines. That information is not accurate in some engines like InnoDB and they are...
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