MySQL : Open-Source, Relational Database Management System

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MySQL Error Reading Communication Packets

In MySQL error logs, I see these quite few a warnings like these: 120611 16:12:30 [Warning] Aborted connection 2619503 to db: 'db_name' user: 'user_name' host: 'webapp_hostname' (Got an error reading ...
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2answers
5k views

Set up a MySQL slave using mysqldump to get the initial data

I have a master database which already has some data in it. The tables in the master database include both MyISAM and InnoDB engines. Now I want use mysqldump to dump the initial data of my slave ...
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4answers
6k views

Why does MySQL not have hash indices on MyISAM or InnoDB?

I have an application that will only select on equality, and I figure I should use a hash index over a btree index. Much to my dismay, hash indices are not supported on MyISAM or InnoDB. What's up ...
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2answers
5k views

Dump only the Stored Procedures in MySQL

I need to dump only the stored procedures : no data, no table creation. How can I do this using mysqldump?
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2answers
7k views

Is InnoDB Engine up to speed against Memory Engine?

I am exploring the efficiency of different database engines in MySQL version 5.5.18 to see which is best suited for use with a range query on a dataset of 5 million rows: SELECT P.col1, P.col2, ...
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1answer
873 views

Configured MySQL replication but its not working

I have configured MySQL master and slave replication setup on 5.5.x. But for some reason data is not getting replicated properly. What might be the reason? At Master: /etc/my.cnf [mysqld] ...
3
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3answers
3k views

Mysql users deleted

I have a fresh centos 6.2 with mysql in 5.1.52. Then I saw two empty user name and I deleted that then I saw 3 root user deleted that and created one like this CREATE USER 'root'@'%' IDENTIFIED BY ...
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3answers
4k views

Disable trigger for just one table

Is it possible to disable a trigger momentarily but for just one table. For example I have table, TableA with an on insert, update and delete trigger. I also have a table B with the same triggers but ...
3
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2answers
2k views

Separate tables or partition one huge table?

I'm building a rather large table that includes a particular column, my_column. There are a small-ish number of possible values for my_column, and each unique value of my_column should have the same ...
3
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2answers
1k views

Concurrently update with limit mysql

I want to know if concurrently UPDATE .... LIMIT N will not overlap with more than one client querying the db. After UPDATE ... LIMIT N the client will make a SELECT with some client_id assigned. I ...
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2answers
180 views

Why is MySQL not using the index with the higher cardinality?

I have an index called source with cardinality of 1122 and a second index called state with cardinality of 22. MySQL keeps using the state index when when query SELECT C1 FROM tbl WHERE source = 'x' ...
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5answers
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In MySQL, does the order of the columns in a WHERE clause affect query performance?

I am having performance issues on certain database queries that have large possible result sets. The query in question, I have three ANDs in the WHERE clause Does the order of the clauses matter? ...
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1answer
14k views

INT(5) vs SMALLINT(5)

In MySQL table definitions is there a different between INT(5) and SMALLINT(5)? Or do they both represent the same size?
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3answers
2k views

Why doesn't InnoDB store the row count?

Everyone knows that, in tables that use InnoDB as engine, queries like SELECT COUNT(*) FROM mytable are very inexact and very slow, especially when the table gets bigger and there are constant row ...
7
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2answers
2k views

MySQL deadlock - cannot restart normally?

MySQL version 5.5.13-1 A snippet from the SHOW ENGINE INNODB STATUS\G: LATEST DETECTED DEADLOCK ------------------------ 111218 10:22:34 *** (1) TRANSACTION: TRANSACTION 1318D95B, ACTIVE 0 sec ...
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2answers
4k views

Ibdata usage and Recommendations?

I have a Production server On November 5,2011 the ibdata size was 100G. In Approximate 3 months it is increased to 200G.So it has just doubled its size.So it is a Huge Data.Currently lvm is 251G. I ...
5
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1answer
819 views

Can I have an InnoDB master and MyISAM slaves with Full-Text for searching?

I'd like to use InnoDB on the master, for its transactional ability, but MyISAM on the slaves for the full-text search ability. Is this possible?
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2answers
1k views

Why does MySQL choose this execution plan?

I have two queries, select some_other_column from `table` order by primary_index_column asc limit 4000000, 10; and select some_other_column from `table` order by secondary_index_column asc ...
4
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1answer
3k views

How do I reduce the database size on AWS RDS MySQL?

I have an RDS MySQL database on Amazon Web Services. I want to reduce the size of the database in the control panel in order to save money. Q: How do I make it smaller? Their site says you have to ...
4
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2answers
1k views

Help with this SELECT in the same table

I have this table structure: id1 id2 1 2 1 3 1 4 2 1 2 5 I need to build a query to select id2 where id1 is not in id2. For example if id1 = 1 then only id2=3 and id2=4. I tried ...
4
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2answers
2k views

What happens when InnoDB hits its tablespace autoextend max?

The latest version of High Performance MySQL (3rd ed.) recommends that one: ...place an upper limit on the tablespace's size to keep it from growing very large, because once it grows, it doesn't ...
3
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1answer
2k views

Is there a MySQL engine or trick to avoid writing so many temp tables to disk?

I've got a web application connected to a database running MySQL. Here's the problem: a not insignificant number of queries create temporary tables and many of the tables involved have BLOB fields. ...
3
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1answer
104 views

Screwed up replication by sharing server ids

So I had my screwup for the week today. I was adding another pair of slaves and set the same server ID on the new slave as an old slave. The layout kind of looks like Master | | \/ | oldS | ...
3
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1answer
4k views

Mysql master-master replication auto flush old logs

I have mysql-5.1.41 master-master setup running on ubuntu machines and below is the configuration of a master: skip-host-cache skip-name-resolve event_scheduler = ON max_connections = 500 ...
2
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2answers
579 views

MySQL on SSD - what are the disadvantages? [closed]

Recently, I heard that I should not host my MySQL database on an SSD drive because there is a big chance of disk failure and data lost. Given that 20% of all queries in my database are INSERTs and ...
2
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1answer
1k views

importing myisam 5.0 database into a 5.5 innodb server

I have MySQL 5.0 and 5.5 servers (but not a 5.1 server). The 5.0 server is myisam only, the 5.5 default is innodb. I need to move a database from the 5.0 server to the 5.5 server. The database is ...
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2answers
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Less restrictive query return less result due to simple removing one additional constraint

Look at this query SELECT DISTINCT TB.ID, TB.Latitude, TB.Longitude, 111151.29341326*SQRT(pow(-6.185-TB.Latitude,2)+pow(106.773-TB.Longitude,2)*0.98839228980165) AS Distance FROM ...
6
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2answers
2k views

Why does MyISAM support FULLTEXT Searching and InnoDB does not?

I know the basic differences between the MyISAM and InnoDB engines. In MySQL 5.6 beta, InnoDB will support fulltext search. But, I wonder why previous versions of InnobDB didn't support FTS? My guess ...
5
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1answer
329 views

“Site Offline” MySQL server failing to start and stop

I'm hosting a few sites on linode and have encountered a strange problem. For the last two years the site has been running perfectly fine, and now randomly all the websites on the server go to the ...
5
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1answer
1k views

Replicate MySQL 5.0 Master to 5.5 Slave?

We're planning out a series of server/software upgrades and were curious. We have a RHEL5 install running MySQL 5.0 that we'd like to replicate to a new (virtualized) server running CentOS 6 and ...
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3answers
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What are the limits on the amount of slaves per master?

I currently have a Master with 2 slaves, all running MySql 5.5. What are the limitations on the amount of slaves I can connect to a single master? what parameters should be taken into affect?
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1answer
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What can cause TRUNCATE TABLE to take a really long time?

I'm running MySQL5.5 with Master/Slave replication (1 master, 2 slaves). I have a process that runs once a week and truncate a specific table. The table is not large and only has a few thousands ...
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2answers
472 views

Why is a secondary index chosen over a clustered index for SELECT COUNT(*) …?

In this query: select count(*) from largetable; a secondary index is chosen: mysql> explain select count(*) from largetable; ...
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4answers
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Call a stored procedure from a trigger

I have created a stored procedure in mysql using the following syntax. DROP PROCEDURE IF EXISTS `sp-set_comment_count`; DELIMITER $$ CREATE PROCEDURE `sp_set-comment_count` (IN _id INT) BEGIN -- ...
4
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1answer
2k views

Suddenly have to rebuild indexes to prevent site from going down

I have been having this problem for a while: http://stackoverflow.com/questions/7770695/mysql-query-slow-until-reindex-column It seems all is good and when I suddenly get a lot of writes to the table ...
4
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1answer
991 views

Determining max database and table size supported and present size

One of my MySQL databases has been running on a single PC from the last four years. Here is my setup: MySQL 5.5.14 Windows XP on NTFS partition All of my tables are using InnoDB engine Here are ...
4
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2answers
730 views

With MySQL Replication, what level of resilience is possible?

I've found lots of good material on setting up MySQL replication, but not much on what to do in the event of failures. Understanding the degree of resilience I can achieve is fundamental to designing ...
4
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3answers
563 views

Separate databases for front-end and back-end

The site I am working on has a lot of backend/cron activity, so there are between 5 and 15 queries being executed every second of the day. This can slow down page loads by a second or more. I was ...
3
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1answer
126 views

What if I want to keep using MyISAM

In my current use of MyISAM the databases are extremely small and kept for a few weeks after which time they are deleted and completely rebuilt with a clean slate. The script uses MYISAM tables and ...
3
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1answer
1k views

Binlog has bad magic number

I keep getting this error whenever I start MySQL. 121028 1:38:55 [Note] Plugin 'FEDERATED' is disabled. 121028 1:38:55 InnoDB: The InnoDB memory heap is disabled 121028 1:38:55 InnoDB: Mutexes and ...
3
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1answer
505 views

Select * from statement execute very slowly, innodb io read speed is low

I have a very simple query " select * from ap_statistic " running in my servers. the servers have the same hardware and software configuration (CPU 8 core, mem :32G, OS: redhat 5.5, mysql version: ...
3
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1answer
3k views

error 1118: row size too large. utf8 innodb

I have tried to find a solution guys, and I am guessing that someone has met this before. But I cannot get hits down below 5000... most of which don't match my question. Using MySQL 5.6 - windows ...
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2answers
4k views

Trying to understand SHOW SLAVE STATUS\G

I have slave setup and looks like it is running fine. Below is a snapshot of it. show slave STATUS\G; *************************** 1. row *************************** Slave_IO_State: ...
3
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2answers
564 views

Sorting the Table and getting the position

I am able to sort a table using the following code:SELECT * FROM Persons ORDER BY LastName But I wanted to get the ranking/position of a person using that order. For example when I sort Person table ...
3
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1answer
1k views

Does `Seconds_Behind_Master` show exact Slave Lag from Master?

Does Seconds_Behind_Master show the correct result? I have also Implemented the mk-heartbeat replication monitoring. It was showing the other result in comparison with Seconds_Behind_Master. Which ...
3
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1answer
463 views

MySQL query 'going away' on executing INSERT ON DUPLICATE UPDATE statement with a 12524 character blob

I have a mysql insert on update query like so insert into table (col1, col2, col3) values (1,2,'huge blob with 12524 chars') on duplicate key update col3 = 'huge blob with 12524 chars'; col1, col2 ...
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1answer
1k views

Stuck outside MySQL! XAMPP - help please

I have been using xampp (on windows XP/XAMPP 1.7.4 /PHP 5.3.5) for quite a while now, and last morning I started to get some weird messages when I was developing my website, It happened yesterday and ...
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4answers
8k views

Specified key was too long; max key length is 1000 bytes in mysql 5.6

one of the application server is internally creating the database on my mysql but when ever the following create table command gets executed CREATE TABLE ofRoster ( rosterID ...
2
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1answer
6k views

How can extract the table schema from just the .frm file?

I have extracted the data directory of mysql from a backup and need to get the schema from an old table, however it's a backup from a different machine. I have read a fair number of tutorials today ...
2
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1answer
919 views

MySQL upgrade 5.0.88 to latest

Very interesting and informative blog.. I have a question - i have a requirement of upgrading from 5.0.88 to latest version.. Why should i upgrade? if so, which version should i consider? What ...