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Search Results for: redundant index

Redundant index is not always bad

About year ago Peter wrote about redundant indexes and mentioned sometimes it is good to leave two indexes, even one is first part of another. I’m speaking about BTREE indexes, for example, KEY (A), and …


Duplicate indexes and redundant indexes

About every second application I look at has some tables which have redundant or duplicate indexes so its the time to speak about these a bit. So what is duplicate index ? This is when …


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 schema, online DDL and several other InnoDB and …


Find and remove duplicate indexes

Having duplicate keys in our schemas can hurt the performance of our database: They make the optimizer phase slower because MySQL needs to examine more query plans. The storage engine needs to maintain, calculate and …


Extending Index for Innodb tables can hurt performance in a surprising way

One schema optimization we often do is extending index when there are queries which can use more key part. Typically this is safe operation, unless index length increases dramatically queries which can use index can …


How Percona does a MySQL Performance Audit

Our customers or prospective customers often ask us how we do a performance audit (it’s our most popular service). I thought I should write a blog post that will both answer their question, so I …


Getting MySQL to use full key length

There is one bug, or “missing feature” in MySQL Optimizer which may give you hard time causing performance problems which may be hard to track down, it is using only part of the index when …


A technical WebScaleSQL review and comparison with Percona Server

The recent WebScaleSQL announcement has made quite a splash in the MySQL community over the last few weeks, and with a good reason. The collaboration between the major MySQL-at-scale users to develop a single code …


TokuMX tip: Create any field name you want

A common MongoDB tip is to create short field names to save storage space. Because MongoDB does not compress its data on disk and stores field names in each document, using longer field names leads …


Data compression in InnoDB for text and blob fields

Have you wanted to compress only certain types of columns 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 …