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Search Results for: query count rows of all tables in access

New OLAP Wikistat benchmark: Introduction and call for feedbacks

I’ve seen my posts on Ontime Air traffic and Star Schema Benchmark got a lot of interest (links: https://www.percona.com/blog/2010/01/07/star-schema-bechmark-infobright-infinidb-and-luciddb/ https://www.percona.com/blog/2009/10/02/analyzing-air-traffic-performance-with-infobright-and-monetdb/ https://www.percona.com/blog/2009/10/26/air-traffic-queries-in-luciddb/ https://www.percona.com/blog/2009/11/02/air-traffic-queries-in-infinidb-early-alpha/ ). However benchmarks by itself did not cover all cases I would want, …


Missing Data – rows used to generate result set

As Baron writes it is not the number of rows returned by the query but number of rows accessed by the query will most likely be defining query performance. Of course not all row accessed …


Database access Optimization in Web Applications.

This is pretty simple approach I often use called to optimize web application performance if problem happens with few pages. If we have “everything is slow” problem looking at slow query logs may be better …


INSERT INTO … SELECT Performance with Innodb tables.

Everyone using Innodb tables probably got use to the fact Innodb tables perform non locking reads, meaning unless you use some modifiers such as LOCK IN SHARE MODE or FOR UPDATE, SELECT statements will not …


Why MySQL could be slow with large tables ?

If you’ve been reading enough database related forums, mailing lists or blogs you probably heard complains about MySQL being unable to handle more than 1.000.000 (or select any other number) rows by some of the …


‘Indexing’ JSON documents for efficient MySQL queries over JSON data

MySQL meets NoSQL with JSON UDF I recently got back from FOSDEM, in Brussels, Belgium. While I was there I got to see a great talk by Sveta Smirnova, about her MySQL 5.7 Labs release …


InnoDB’s multi-versioning handling can be Achilles’ heel

I believe InnoDB storage engine architecture is great for a lot of online workloads, however, there are no silver bullets in technology and all design choices have their trade offs. In this blog post I’m …


DBA 101: Sometimes forgotten functionality in the MySQL client

The MySQL client has some functionalities some of us never use. Why would you use them and what is the added value of this? Every DBA and developer has had a moment when he or …


The power of MySQL’s GROUP_CONCAT

In the very early days of Percona Vadim wrote very nice post about GROUP_CONCAT. But I want to show you a bit more about it. When is GROUP_CONCAT useful? Usually while working with Support customers …