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Non-Deterministic Order for SELECT with LIMIT

 | April 7, 2017 |  Posted In: Insight for DBAs, MySQL

Non-Deterministic Order

In this blog, we’ll look at how queries in systems with parallel processing can return rows in a non-deterministic order (and how to fix it). Short story: Do not rely on the order of your rows if your query does not use ORDER BY. Even with ORDER BY, rows with the same values can be sorted differently. To fix this […]

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Column Store Database Benchmarks: MariaDB ColumnStore vs. Clickhouse vs. Apache Spark

 | March 17, 2017 |  Posted In: Apache Spark, Big Data, Column Store Database, MySQL

Column Store Database

This blog shares some column store database benchmark results, and compares the query performance of MariaDB ColumnStore v. 1.0.7 (based on InfiniDB), Clickhouse and Apache Spark. I’ve already written about ClickHouse (Column Store database). The purpose of the benchmark is to see how these three solutions work on a single big server, with many CPU cores and large amounts of […]

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ClickHouse: New Open Source Columnar Database

 | February 13, 2017 |  Posted In: Benchmarks

Clickhouse

For this blog post, I’ve decided to try ClickHouse: an open source column-oriented database management system developed by Yandex (it currently powers Yandex.Metrica, the world’s second-largest web analytics platform). In my previous set of posts, I tested Apache Spark for big data analysis and used Wikipedia page statistics as a data source. I’ve used the same data as […]

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MySQL 8.0: Descending Indexes Can Speed Up Your Queries

 | October 20, 2016 |  Posted In: MySQL

MySQL 8.0.1

In this blog, we’ll discuss descending indexes in MySQL 8.0. Summary The future MySQL 8.0 will (probably) have a great new feature: support for index sort order on disk (i.e., indexes can be physically sorted in descending order). In the MySQL 8.0 Labs release (new optimizer preview), when you create an index you can specify the […]

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Upgrading to MySQL 5.7? Beware of the new STRICT mode

 | October 18, 2016 |  Posted In: MySQL

STRICT mode

This blog post discusses the ramifications of STRICT mode in MySQL 5.7. In short By default, MySQL 5.7 is much “stricter” than older versions of MySQL. That can make your application fail. To temporarily fix this, change the SQL_MODE to NO_ENGINE_SUBSTITUTION (same as in MySQL 5.6):

MySQL 5.7, dates and default values The default SQL_MODE in MySQL 5.7 […]

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MySQL 5.7 Performance Tuning Immediately After Installation

 | October 12, 2016 |  Posted In: InnoDB, MySQL

MySQL 5.7 Performance Tuning

This blog updates Stephane Combaudon’s blog on MySQL performance tuning, and covers MySQL 5.7 performance tuning immediately after installation. A few years ago, Stephane Combaudon wrote a blog post on Ten MySQL performance tuning settings after installation that covers the (now) older versions of MySQL: 5.1, 5.5 and 5.6. In this post, I will look […]

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MySQL 8.0: The end of MyISAM

 | October 11, 2016 |  Posted In: MySQL

MySQL 8.0.1

This blog discusses the gradual end of MyISAM in MySQL. The story that started 20 years ago is coming to its end. I’m talking about the old MyISAM storage engine that was the only storage provided by MySQL in 1995, and was available in MySQL for 20+ years. Actually, part of my job as a MySQL consultant […]

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