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

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stress testing mysql - maximizing qps for a single user

I am running a stress test and I am trying to churn out as much qps as I can for a single user. I know this is a loaded question so I will try to be more specific. Trying to target 30,000 qps with a ...
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44 views

Will composite indexes or unique indexes help with query performance?

I need help with identifying indexes to increase performance of the following query. I'm currently using v5.5 with InnoDB. I cannot modify the query. However, I can add indexes as needed. The ...
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26 views

How can I determine the performance (rows/second) for a certain query on one of my tables?

I want to find the performance (rows/second) for an UPDATE query on one of my tables so I can adjust my WHERE clause to select an appropriate number of records. The table has around 10 million rows. ...
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97 views

Slow queries InnoDB occasionaly

I have the next table: CREATE TABLE `sessions` ( `session_id` char(32) COLLATE utf8_unicode_ci NOT NULL, `session_expires` int(11) NOT NULL DEFAULT '0', `session_data` varchar(10000) COLLATE ...
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1answer
55 views

How can I make multiple joins on the same table?

I have a table (signal) which contains references to two other tables (ee and eeav). I want to perform an SQL Query which combines the data from ee and eeav tables. The situation is as follows: The ...
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23 views

How to ensure accents are view as different characters when adding to unique indexes?

What can I do to ensure MySQL views the following as two different values? Bee Bée When I try to create a unique index, it fails because they're the same value. I looked at the following thread, ...
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2answers
3k views

How to outer join multiple tables to retrieve uncommon records

I'm trying to do an outer join in MySQL to identify records not common to 3 tables. Here's my current effort http://sqlfiddle.com/#!2/02b92/30 I'm trying to retrieve the records not common to all ...
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1answer
28 views

Is it possible to find the user whose aggregated score reaches X value first?

Given this sample fiddle containing sales value and date for two users: http://sqlfiddle.com/#!2/8148be/3 How can I find the first user who has reached a total saleValue of 30 since the beginning of ...
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117 views

Is there a way to truncate the microseconds of a CSV value when importing data using LOAD DATA INFILE?

I'm loading data using LOAD DATA INFILE in 5.5 where the value includes microseconds. I must use DATETIME data type. Currently, I'm using regular expressions to remove them from the CSV prior to ...
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2answers
114 views

Buffer pool above 90% utilized causes MySQL to crash

Without getting deep into the architecture and setup, is it common behavior for MySQL to act in this manner? EDIT I'm using Rolando's script to identify how full the innodb_buffer_pool is. SELECT ...
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14 views

How to recover from a corrupt relay file on a slave?

I recently had a master shutdown on its own. In this case, the slaves all recovered fine. However, I starting thinking about how to recover if the master shuts down and for some reason the relay log ...
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1answer
136 views

database design for dynamic menu bar [closed]

I am trying to create a menu bar which will load dynamically on user log in, based on the user roles. Say if the user is an admin he can see all the items listed under the header and if a user is a ...
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27 views

How to return nothing but the number of rows and execution time?

I'm trying grab the # of returned rows and execution time rather than the actual records. Or,at the very least discard the results. Any tricks to do this? I could use outfile or SP and then parse it, ...
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1answer
800 views

How to resolve “Error log file size is increasing in mysql 5.5” issue w/o restarting mysql

I have an Ubuntu server with MySQL 5.5 installed. In /var/lib/mysql a .err file is kept on updating with these warnings only: [Warning] IP address '234.22.11.221' could not be resolved: Temporary ...
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122 views

How to decrease load time by chunking large file using Percona pt-fifo-split?

I'm loading data into a fresh instance which takes ~48s to load a single file (1G; 2.5m rows). To decrease load time, I tried chunking it into 100k rows using Percona's pt-fifo-split. Unfortunately, ...
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1answer
43 views

Will MySQL redirect a read request to the master after a certain time? [closed]

I can't find what variable controls this or any information about the time limit. Thanks!
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1answer
83 views

How to find the length of multiple column index in MySQL

Is there a way to find out what is the length in bytes for the unique index (NKU) key created through the following command: CREATE TABLE test_ ( testId bigint(20) NOT NULL, name varchar(75) ...
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2answers
2k views

MySQL COUNT Query taking too long time to execute

I have below query that takes 7 secs to run SELECT COUNT(*) AS `count` FROM `yuldi`.`businesses` AS `Business` LEFT JOIN `yuldi`.`businesses_categories` AS `BusinessesCategory` ON ...
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2answers
66 views

Are relay logs necessary for replication?

I'm trying to understand when/where using relay log is beneficial. According the documentation, mysql captures and writes events from the master's binary log as the result of the I/O thread. Then, the ...
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2answers
201 views

Nested query efficiency in MySQL

I have a table with several attributes like this: id id2 attribute -------------------------------- 1 100 blue 2 100 red 3 100 green 4 100 white 5 102 blue 6 102 green 7 102 ...
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20 views

How is the key length determine in an index?

Aside from explicitly setting the key length when creating an index, how does MySQL determine the appropriate key len shown when running "explain"? Thanks
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12 views

Is there any value in adding a pk column to an composite index? [duplicate]

I recently inherited a database with indexes that contain the table's primary key as part of some composite indexes. Given MySQL adds a hidden column representing the PK regardless of whether you ...
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1answer
27 views

Is there any value in adding an already indexed column to a composite index?

The title says it all. Does the query optimizer see composite indexes where each column is already indexed as redundant? Or, is it used when each of the composite index's columns are in the WHERE ...
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1answer
85 views

Migrating MyISAM tables from 5.5 => 5.6

I was wondering if anyone had any pointers on migrating MyIASM tables from mysql 5.5 to 5.6, specifically using Percona builds, via an rsync? Is this safe? I know we need to do a full ...
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2answers
47 views

How can I store least used table files to a slower drive?

Is it possible to separate the least used and most frequently used data files on to separate disks when using InnoDB?
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573 views

Mysql 5.5 InnoDB growing CPU - Going crazy

Good morning, I'm currently facing a problem where CPU usage keeps going up until the server crash. I've tried multiple best practices proposed in this forum and on Percona, reinstalled the server ...
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1answer
39 views

How to decipher the transaction message in innodb status log.

I have several transactions that seem have stalled. Looking at the innodb status log, I found several messages similar to the following: ---TRANSACTION 69DBBB, ACTIVE 947 sec starting index read, ...
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1answer
140 views

How to store temp tables in memory during table “optimize”?

When optimizing tables, SHOW PROCESSLIST lists it as "copying to tmp table". I'm trying to ensure the copy takes place in memory to speed up the process. I've tried adjusting the tmp_table_size to ...
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3answers
140 views

Will redirecting queries to dev/null warm up indexes?

I'm trying to warm up the buffer pool. Will running a query and re-directing the output to /dev/null suffice? e.g. mysql -u username -p -e "select id from tbl where 1=1" > /tmp/results.txt Thanks
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2answers
92 views

MYSQL: Join with many to many

I'm trying to create a view and trying to see what can be done, I have a main table a table I want to join to and also a junction table. Event table (it's very big so it's just dummy data): ...
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2answers
54 views

Mysql Master Offline

In a unidirectional Master-Slave setup, should the slave be manually stopped in cases where the Master is offline due to Maintenance, Crash etc. ? Or should one just leave it so that it keeps trying ...
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1answer
148 views

What is the difference between uniqe index/unique/unique key/unique constraint keywords?

I am using mysql 5.5.16 What is the difference between the following DDL statements? 1) create table sql_query ( id int not null , query_text varchar(21826) not null , query_md5 ...
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150 views

MySQL Slave not updated

This might be a duplicate of questions on the same problem asked before. But all the suggestions to the previous questions do not seem to work in my case. I have set up Replication using SSH Tunnel. ...
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2answers
758 views

Fastest way to create local copy of live InnoDB MySQL database?

We have a MySQL database (InnoDB) on our live Ubuntu 12.04 server which has grown quite large (25gb+). Every month or so we need to copy this database to our development machines to work on locally. ...
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193 views

How to create two same name databases in two different MySQL users?

I am using MySQL 5.5 running on Ubuntu 12.04. I have created two different users as 'root' and 'abc' and I want to create 'Items' database in this both user accounts but I want this two databases ...
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1answer
789 views

Space not reclaimed after dropping MyISAM table

I just dropped a rather large MyISAM table (~4 gb); it was 350k rows with about 11k of data per row. However, when I run df -h on my database server, I am still at 100% disk usage, so much so that I ...
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226 views

#2002 Cannot log in to the MySQL server / Connection for controluser as defined in your configuration failed

I use PHP/MySQL in Ubuntu 13. To reduce the size of ibdata1, i followed this post What is the best way to reduce the size of ibdata in mysql? and make necessary changes as told in the answer. I did ...
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27 views

How to acheive Concurrency in mysql when there is 500+ request simultaneously to the server

I am using Mysql (InnoDb), in this I am facing problem when we checked the curl request upto 500 connection at a time (simultaneously) but when we try more than that then my servers goes to idle ...
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2answers
531 views

How can I execute multiple statements at once in MySQL Workbench?

I'm trying to execute multiple LOAD DATA INFILE statements at once using MySQL Workbench. However, they execute one at a time. Anyway of forcing them to run in parallel? Thanks for the help!
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127 views

How to verify data dumps between two MS SQL and MySQL

I'm trying to verify data exported from MSSQL and imported into MySQL is 100% accurate using MD5 hash. On Linux, I'm using md5sum and WinMD5 on Windows. The encoding is the same: UTF8. I tried both ...
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2answers
142 views

Is there a rule of thumb regarding the size and number of a buffer pool instances?

I know the consensus seems to be approximately 75% of ram should be dedicated to the buffer pool. But, I'm more interested in the optimal number of buffer pool instances. What are some things to ...
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1answer
66 views

MySQL: How to calculate potential wait time?

I'm trying understand the relationship between WAIT_MS and COUNT_STAR. Is this saying the average wait time is 3.2s and occurred 11,543 times for a total of approximately 10.5hrs of aggregate wait ...
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1answer
447 views

How to overwrite csv file of MySQL result set?

My SQL query is given below, select company.Company_name as COMPANY_NAME, IFNULL(followup.contact_date, ' ') AS FOLLOW_UP_DATE, IFNULL((select Full_name from user where user_id = followup.user_id), ...
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1answer
288 views

update variable from multiple tables in one row

I have two databases, and I need to UPDATE variable 'birthday' from one row to another checking 'name' (from db1 to db2). The problem is, that 'name' variable in second db is located in another table ...
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67 views

How to update Status using IF Condition in Mysql trigger

I'm trying to write an update trigger that will Design_Update_Status to Customized when a date is entered in Custom_Design_Update_Date field and if nothing is entered that field it should update ...
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2answers
7k views

ALTER TABLE - Rename a column

This got me nuts! I want to rename a column from read-more to read_more in blog table Tried all this: ALTER TABLE blog RENAME COLUMN read-more to read_more; ALTER TABLE blog CHANGE COLUMN ...
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68 views

Need help on query optimization in MySQL

Below is the query, I need to optimize it. It is using subquery, I need to re-write it using join how to do this SELECT Client_ID FROM SQL_AuditPro.clients c WHERE (SELECT ...
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113 views

MySQL is not logging queries into log file

I am using MySQL 5.5 with Amazon Linux 2013. Following is my configuration for log file. slow_query_log = 1 long_query_time=0 log-error = /var/log/mysqld.log slow_query_log_file = ...
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257 views

How should I config the my.ini(or my.cnf) file for mysql?

Thanks for taking your time to look at my question, and I hope that you can help me with this. I have a Windows Server 2012 server, it has: Memory : 3840MB Ram Processor: Intel(R) Xeon(R) CPU ...
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54 views

What's the complexity of renaming a column in MySql?

We want to rename a column in our MySql (version 5.5) database with something like this: ALTER TABLE t1 CHANGE a b INTEGER; Is this an O(N) (N=number of rows in the table) or an O(1) operation? I ...