Search Results for: how to count single column value in mysql code

MySQL Users Conference – Innodb

It might look like it is too late to write about stuff happened at Users Conference but I’m just starting find bits of time from processing accumulated backlog. The Theme of this Users Conference was surely Storage Engines both looking at number of third party storage engine presented, main marketing message – Storage Engine partnership […]

MySQL Prepared Statements

If you care about archiving best performance in your application using MySQL you should learn about prepared statements. These do not neccesary provide performance beneft but they may, they also have other benefits. As a quick introduction – before MySQL 4.1 there were only textual statements and textual protocol for data transfer – query was […]

INSERT ON DUPLICATE KEY UPDATE and summary counters.

INSERT … ON DUPLICATE KEY UPDATE is very powerful but often forgotten MySQL feature. It was introduced in MySQL 4.1 but I still constantly see people unaware of it. Myself I like this feature big deal because it is designed in truly MySQL style – very efficient solution for freqent task while keeping it beautiful […]

Store UUID in an optimized way

A few years ago Peter Zaitsev, in a post titled “To UUID or not to UUID,” wrote: “There is timestamp based part in UUID which has similar properties to auto_increment and which could be used to have values generated at same point in time physically local in BTREE index.” For this post I’ve rearranged the timestamp part […]

When (and how) to move an InnoDB table outside the shared tablespace

In my last post, “A closer look at the MySQL ibdata1 disk space issue and big tables,” I looked at the growing ibdata1 problem under the perspective of having big tables residing inside the so-called shared tablespace. In the particular case that motivated that post, we had a customer running out of disk space in his […]

Is Synchronous Replication right for your app?

I talk with lot of people who are really interested in Percona XtraDB Cluster (PXC) and mostly they are interested in PXC as a high-availability solution.  But, what they tend not to think too much about is if moving from async to synchronous replication is right for their application or not. Facts about Galera replication […]

Avoiding auto-increment holes on InnoDB with INSERT IGNORE

Are you using InnoDB tables on MySQL version 5.1.22 or newer? If so, you probably have gaps in your auto-increment columns. A simple INSERT IGNORE query creates gaps for every ignored insert, but this is undocumented behaviour. This documentation bug is already submitted. Firstly, we will start with a simple question. Why do we have […]

Shard-Query adds parallelism to queries

Preamble: On performance, workload and scalability: MySQL has always been focused on OLTP workloads. In fact, both Percona Server and MySQL 5.5.7rc have numerous performance improvements which benefit workloads that have high concurrency. Typical OLTP workloads feature numerous clients (perhaps hundreds or thousands) each reading and writing small chunks of data. The recent improvements to […]

Debugging problems with row based replication

MySQL 5.1 introduces row based binary logging. In fact, the default binary logging format in GA versions of MySQL 5.1 is ‘MIXED’ STATEMENT*;   The binlog_format  variable can still be changed per sessions which means it is possible that some of your binary log entries will be written in a row-based fashion instead of the […]