MySQL 5.5 brought many performance enhancements and expanded the feature set of the popular open-source RDBMS.

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Emulating WITH clause in MySQL/query perfomance review

I have never really worked with MySQL queries till this last week. I was tasked with making a simple tool for my department that tracks contacts. Here are the 2 tables and the type of data they ...
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95 views

Understanding Indexes and using them better

I've been spending some time trying to optimise our MySQL queries that we use which essentially joins one table with 2 million rows onto another which has 1-2 million. I know MySQL is able to easily ...
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26 views

How do I recover from MySQL InnoDB table/index corruption?

While trying to upgrade a database (in place) I got the following error. The server starts up and everything seems to be fine, except that the table mentioned in the message is no longer accessible. ...
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120 views

Lost Connection to mysql server at 'reading authorization packet', system error 0"

OK, this has been bugging me all afternoon now, I have a new MySQL Database '5.5.40-0+wheezy1-log' running on Debian Linux. It is to all extents and purposes a clean install. I have created two ...
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30 views

pt-online-schema-change with circular replication

So I have an alter table (adding 4 columns) to do on a fairly large table (74 million rows). The problem is this table has firstly to remain online and writable during the whole operation and ...
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263 views

What to do with unused RAM on a MySQL database server?

For years I have been running dedicated servers with more or less limited ressources, resulting in unsatisfying performance of the web application (Drupal). Tools like Matthew Montgomery's MySQL ...
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65 views

Refactoring IN Subquery, Avoiding Query in a Loop

I've got a table which was designed as both the current data set for participants, as well as being the historical changeset for those participants. This table has been in use for approximately three ...
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81 views

MySQL query with order by decreased performance

Here is my schema: CREATE TABLE `UserMst` ( `UserID` mediumint(8) unsigned NOT NULL AUTO_INCREMENT, `EMailID` varchar(50) DEFAULT NULL, `UserName` varchar(20) DEFAULT NULL, `FullName` ...
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51 views

crossplatform mysql_install_db script in mysql 5.5.34 on Windows

I downloaded mysql-5.5.34-win32.zip and found out there is mysql_install_db.pl script. However mysql 5.5 documentation says: mysql_install_db is a shell script and is available only on Unix ...
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195 views

Upgrading from MySQL 5.5 to 5.6 - timestamp issue?

I'm looking at upgrading my Percona Server setup from 5.5 to 5.6. Reading the upgrade docs from MySQL sounds mostly straightforward except for anything involving time/date columns. As far as I can ...
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2k views

Why does CAST(1 AS SIGNED INTEGER) return a BIGINT on MySQL?

If I do CAST(1 AS SIGNED INTEGER) I always end up getting a BIGINT returned, for example: $ mysql -u root -p --column-type-info Enter password: --- Copyright and help message snipped for brevity --- ...
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635 views

Fastest way to perform simple operations on 1 million rows

I have a simple table with more than 1 million rows in an InnoDB MySQL table. Here are the steps that I need to perform on each row: SELECT * FROM tbl where work_done=0 make some data processings ...
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34 views

table scheme definiation it this way that insert duplicate into another table

I have a table in which there is a column name with SP varchar(10) NOT NULL. I want that column always to be unique so i created unique index on that column . My table schema as follows : CREATE ...
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443 views

Incorrect information in .frm file after a power outage?

CentOS release 6.3 (Final) x86_64 mysql Ver 14.14 Distrib 5.5.31, for Linux (x86_64) using readline 5.1 SHOW SLAVE STATUS\G: Slave_IO_Running: Yes Slave_SQL_Running: No ...
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500 views

MySQL InnoDB slow inserts

I'm currently struggling with an MySQL Community Server 5.5.27 when inserting large numbers of rows into a table. We're running a 24 core Intel Xeon machine with an SSD software raid array. I did some ...
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22 views

How do I configure MySQL to store specific entire InnoDB tables on a different drive in Windows ( Server )?

After skimming the MySQL ( 5.5 ) docs on Partitioning, that seems to deal with breaking parts of the same table off onto other drives. I'm struggling to find information on how I pinpoint an ...
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509 views

SELECT + INSERT + Query Cache = MySQL lock up

MySQL server seems to constantly lock up and stop responding on certain types of queries and eventually (after couple of minutes of not responding) give up with an error "MySQL server has gone away", ...
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118 views

MySQL Replication - Used to work, now get error 2026

I've had replication running now for about 2 years, with 1 master and 2 slaves. Both are through an SSL connection. I'm using MySQL 5.5.15 on the master (CentOS), and MySQL 5.14.46 on the slaves (on a ...
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44 views

MySQL - Randomly long DESCRIBE queries

I have several queries like this (running on MySQL 5.5): DESCRIBE `TABLE`; And it randomly takes 5-10 seconds on my production servers. We have an ORM that caches this data once per day (per web ...
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168 views

innobackupex: What causes Slave_open_temp_tables did not become zero after waiting 15 minutes?

As you might know, in order to assure a consistent replication state, the slave should be backup only when there are no open temporary tables: ...
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149 views

Error in alter table reorganize partition for MySQL Cluster

My cluster contains 48 million rows and cluster contains 4 storage nodes . After that I add online storage node and executed alter table 'customer_tbl' reorganize partition. Some parameters of ...
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1k views

“Lost connection to MySQL server during query” error

I have MySQL 5.5.20 and this table: mysql> desc country; +----------------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | ...
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42 views

Is there a canonical list of MySQL defaults which should be changed

I'm setting up a new mysql server as we're building a new app at work. Most of the developers/operations guys are familiar with mysql. Many of mysql's settings (eg strict mode) are set badly by ...
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544 views

MySQL cluster stuck in start phase 4, how to proceed?

Over the weekend our cluster we set up for evaluation had one of its data nodes lose network connectivity briefly. This was while another data node was in the middle of a restart (which had been going ...
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106 views

How to create multi volume file backup using symantec backup.exec

I am using symantec backup .exec for backup and restore in mysql server . Now I am in need to take larger database backup in tape .But it exeeds the tape storage and I am trying to create a multi ...
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88 views

How to profile individual queries using PERFORMANCE_SCHEMA

I've been looking at SHOW PROFILES, which seems ideal for what I am doing. However, I've noticed a warning that SHOW PROFILES is being deprecated and that PERFORMANCE_SCHEMA should be used instead. ...
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87 views

MySQL replication backup

How to take MySQL Master-Master and Master-Slave replication backup?. I have setup Master-Master replication with a separate slave for each master on Ubuntu. What happens if, I issue or schedule ...
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185 views

How to speed up this query

MySQL doesn't have nearest neighbor search so. So I try to come up with a "distance" that's reasonable so the number of returned query is around 20-200. That way innodb doesn't have to compute ...
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236 views

mysql server is not sending result set back after query execution to client and staying in sending data state

When I pass a query from my Java application to mysql server, it stays in Sending Data state and not returning result set back to application. When I execute the same query in SQLYog directly, it ...
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5 views

Can MySQL Index Merge an Composite index with a single column index?

I am tuning a query and currently have an index as following : Index 1 : (col1, col2) An example query would be : SELECT * FROM t1 WHERE col1 = '1' AND col3 = '2'; I have created an index on ...
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5 views

Mysql Master - Master Replication

i have established a master A and master B replication between two servers.Both are getting replicated.But it is limited with only one database. My questions 1.How to create a new database in ...
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16 views

Slow Query Performance - Can't Debug

I have a MySQL query that I am trying to debug the performance issue but cannot. I know that the majority of the query is reading/processing rows (Sending Data state). However, in the explain output, ...
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8 views

Oddness with MySQL with InnoDB - CPU capped at 50%

I have MySQL 5.5.22 with InnoDB, running on multiple c3.8xlarge EC2 instances. Which is to say, the VMs are set up with 32 CPUs & 59 GB RAM There are no CPU controls in MySQL, right? Then why ...
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6 views

unable to add data source on idashboard admin

I am in the process of adding data source on iDashboard , Data Source section. So, for that I downloaded the driver from here which is mysql-connector-java-5.0.8-bin-jar and currently trying to enter ...
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2 views

Doctrine and Mysql

This year I have started to use DoctrineORM and ZF2. I design my DB structure in MySql Workbench then sync the code with my test db, staging and production as required. Generally this works very ...
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16 views

How to solve MySql Slave Error 1452 Foreign key constraint fails?

I am site administrator. We use to have a mysql 5.5.40 master(db01) - slave(db02) setup. One day our master server (db01) got down due to hardware failure. So we switched our site to slave (db02) ...
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29 views

Horribly slow MySQL (InnoDB) updates, multiple workers

I've created a PHP daemon that reads records from a MySQL InnoDB-table, analyses it and then updates the record. This process is spread between multiple workers (and servers) using Redis. However, ...
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11 views

Trying to create a trigger to fill two columns (MySQL)

I am trying to create a trigger to update columns on a table when a new record is added to another table. This is the code I am using CREATE TRIGGER `hire` AFTER INSERT ON `hire` FOR EACH ROW BEGIN ...
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10 views

Daemon Waiting for activation in mysql event

When I do, SHOW PROCESSLIST; on mysql, for my event, I see the following result: Q1 )Why does it shows Waiting for next activation all the time? Q2) At times my scheduler turns off which causes my ...
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55 views

Configuration help my.cnf Mysql

Is the following my.cnf file OK for a dedicated server with 56GB of RAM (on ubuntu server and 8 processors)? I'm running just one website on the server and there is a high demand on my cpu from ...
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70 views

Following mysqltuner suggestions: query_cache_size and join_buffer_size

So I am following the suggestions of mysqltuner, and so far I've had great results, the server is performing well (dedicated VPS running a large Magento eCommerce store) There is only two issues left ...
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37 views

MySQL Crash due to “InnoDB Assertion” after Query

Current setup: Ubuntu 12.04 LTS MySQL 5.5.31 Current Use: Slave - Only ETL queries 64 GB RAM Intel(R) Xeon(R) CPU X5670 @ 2.93GHz - 12 Cores - Hyperthreaded (24 Logical) MySQL Main Settings: ...
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30 views

Last synchronization time between master and slave (replication)

During replication process where a Master is connected with slave. Some times connection between these two goes down. Any options to get the details of the last synchronization time?
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30 views

MySQL “ERROR 1005 (HY000): Can't create table 'foo' (errno: 13)”

Windows Server 2008 MySQL 5.5.39 using the root user with full privileges granted to the DB. I know errno: 13 is a permissions issue. I've seen several answers to this for linux where setting ...
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93 views

Incorrect table definition; there can be only one TIMESTAMP column with CURRENT_TIMESTAMP in DEFAULT or ON UPDATE clause

CREATE TABLE approvalreasonexemption ( `id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT, `personId` INT(10) UNSIGNED NOT NULL, `reasonId` INT(10) UNSIGNED NOT NULL, `createdBy` INT(10) ...
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33 views

Best upgrade path for MySql 4.1 to 5.5?

Background Our production environment runs on a system that nobody wanted to update for a long period of time. With a new sherrif in town, we're going to update it. Production is MySql 4.1 with ...
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8 views

Why pages not made young is zero?

In results of Show INNODB Status showed me very weird result: Pages made young 81821279, not young 0 The official statement says: Pages made young, not young: The number of old pages that were ...
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61 views

Too much IO to MySQL InnoDB log files

I am using MySQL version: 5.5.38 I have dedicated HDD to InnoDB log files using innodb-log-group-home-dir option. atopsar -d 30 shows big load (>50%) to this HDD The thing is that I have only 75 ...
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43 views

Soundex on a Large Table

I had a table of names, containing 200,000 rows. This has now been updated to include over 11 million rows. The table is queried using a SOUNDS LIKE 'str' and the result is then passed through ...
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20 views

Unaccounted for MySQL Processes

I am running a MySQL 5.5.38 on a VM running Ubuntu server 12.04. At certain times of the day around 12 mid day, CPU Utilization and loads spikes to over 90% with the MySQLD Process accounting for most ...