MySQL : Open-Source, Relational Database Management System

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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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4answers
4k views

One slave, multiple masters MySql

Is it possible to set-up MySql Replication to have one slave listening to two different masters?
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1answer
1k 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?
5
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1answer
6k views

How to setup replication(Master/slave) in MySQL 5.5.20?

I have two servers both running on MySQL 5.5.20 and I want to setup replication, so every update/insert on Master would reflect immediately on Slave machine. I tried following this tutorial (I used ...
5
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1answer
3k views

What is the difference between XtraBackup and rsync?

Yes, I'm going to run strace on them both... However, I would like to know ... What is XtraBackup is doing over and above rsync -ac src dest ? What's so special about XtraBbackup ? How is XtraBackup ...
4
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3answers
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InnoDB vs MyISAM with many indexes

I am not sure if there is a right or wrong answer to this question, as I suppose it severely depends on the situation, but for the sake of a mental exercise, I'll go ahead and ask it anyway: I have a ...
3
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1answer
14k views

Recover MySQL database from data folder without ibdata1 from ibd files

My WAMP directory accidentally get deleted by another user. Only data folder in MySQLis available. And, in that only database-folders (folders in "\bin\mysql\mysql5.6.12\data\" with name of databases) ...
3
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1answer
12k 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 ...
3
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4answers
6k views

Benefits of BTREE in MySQL

What are the pros and cons of using a BTREE index in MySQL, regarding query speed, disk storage and memory usage? Does BTREE provide easier iteration in increasing order ? What kind of queries would ...
3
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3answers
5k views

Can I specify a different disk for a specific MySQL table?

I use my home machine as my personal database for my hobby analytics project. This machine has an SSD for the main drive where MySQL stores its data. It also has a secondary hard drive that is ...
3
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2answers
2k views

Preventing mysql deadlocks in your php application that uses SELECT… LOCK IN SHARE MODE

If I understand SELECT ... LOCK IN SHARE MODE correctly, you can place it into a mysql transaction to select the rows you will be working with during that transaction. This is done in order to "lock ...
2
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2answers
844 views

Mysql database replication on different vlan/subnet/another site

Saw the posts for "MySQL high availability, failover and replication with Latency" Is it possible to work it in a DR site when its not in the same vlan?
1
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1answer
798 views

Inserting query result to another table hangs on “Copying to temp table on disk” on MySQL

I started the process of inserting returned results to another table. The query groups the rows in respect of indexed IDs. This causes 149,000,000 rows to be decreased to 460,000 rows. The query ...
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5answers
3k views

Is it unwise to run replication on same physical server?

I'm contemplating setting up a Master-Slave replication for my database. The slave server will be used for redundancy and possibly a reports server. However, one of the biggest issues I'm running into ...
4
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2answers
675 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; ...
4
votes
3answers
6k views

What is the mysql.db table used for?

Related to my MySQL issue I have a user with USAGE grant in mysql.user, but in mysql.db this user has Select, Insert, Update, Delete. Thus the user can successfully query the database. I can't find ...
4
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2answers
8k views

DROP PROCEDURE IF EXISTS not included in mysqldump

I'm dumping my stored procedures only using the following command: mysqldump --routines --no-create-info --no-data --no-create-db --skip-opt databasename -u username -p > outputfile.sql but the ...
3
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2answers
1k views

Quick MySQL Backup

I have a database which is grown to 3GB and it has 3 MyISAM tables. And I have 4GB RAM. What will be the best (quick) way to backup this database without any performance lack. Or mysqldump will work ...
3
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3answers
589 views

Dynamically changeable database

We have a database and some data is stored in a Trucrypt folder, my question is how can I include this trucrypt folder. The data type is MyISAM. I saw there is a symbolic link, but not really clear ...
2
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4answers
6k views

Single slave - multiple master MySQL replication

I need to replicate different MySQL databases from multiple servers into a single slave server. How can this be done? is there a way to define multiple master hosts?
2
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1answer
901 views

MySQL Cluster — Storing table data on data nodes

I have setup MySQL Cluster with the MySQL server node and the Management node on a single server, and 2 data nodes (each on a different server for 3 servers in all). After installing, I run ndb_mgm ...
1
vote
1answer
1k views

MySQL service stops after trying to grant privileges to a user

I am using MySQL 5.6, I was trying to create a super user for specific database but I got ERROR 1396 (HY000): Operation CREATE USER failed for 'superuser'@'%' Then I thought maybe there is already ...
1
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1answer
166 views

mysql directory grow to 246G after one query, which failed due to table is full

I was trying to run the following statement with the hope to create a join of two existing tables. create table CRS_PAIR select concat_ws(',', a.TESTING_ID, b.TRAINING_ID, a.TESTING_C) as k, ...
1
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1answer
1k views

mysql restart won't kill child processes on CentOS

I have a mysql database running on a CentOS server. I have noticed that, when left to run for several weeks without restarting the service, then when I need to do a restart (/etc/init.d/mysqld ...
1
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1answer
869 views

Removing/overwriting sensitive data located in already deleted records in ibdata files

As far as I know, using InnoDB tables with innodb_file_per_table = off does not prevent deleted data from being visible in the ibdata1 file. I know this is by-design, and that I could switch the ...
1
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1answer
871 views

decreased performance of stored procedure when migrated from mysql server 5.0 to 5.5

i recently testing the move of our db from one server to another. as part of this process i copied all the data to the new db and started testing it. as a comparison i run a store procedure whose ...
1
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1answer
875 views

Secure method beside phpMyAdmin for remote mysql

Recently, one of my centos linux servers was hacked and the cause of due to phpMyAdmin. It was said due to this problem PhpMyAdmin vulnerability CVE-2011-2505 ...
200
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15answers
79k views

Can MySQL reasonably perform queries on billions of rows?

I am planning on storing scans from a mass spectrometer in a MySQL database and would like to know whether storing and analyzing this amount of data is remotely feasible. I know performance varies ...
7
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2answers
17k views

What is the Best Way to create MySQL Master-Slave Replication Setup and Troubleshoot it?

I am very new to Database Administration. I face a lot of problems while setting up mysql master-slave replication. I also face regular mysql replication troubleshooting issues. Can anybody helps ...
9
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3answers
15k views

How to get the most out of MySQL on a QuadCore machine with 16 GB of RAM?

I'm running a MySQL 5.5 server on my workstation for scientific data analysis and wonder how to configure MySQL in order to get the most out of it performance-wise. The types of query that I typically ...
7
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2answers
13k views

Why do MySQL tables crash? How do I prevent it?

I'm the Administrator of a Moodle site which had its Users table corrupted and it became unusable. Luckily, a simple REPAIR TABLE mdl_user made it work back again. The thing is that I don't know why ...
5
votes
1answer
9k views

InnoDB - High disk write I/O on ibdata1 file and ib_logfile0

Server Specification: VPS with following info model name : Intel(R) Xeon(R) CPU E5649 @ 2.53GHz MemTotal: 2058776 kB MemFree: 244436 kB We are running IP.Board from Invision ...
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2answers
5k views

Performance of a Trigger vs Stored Procedure in MySQL

A post here on DBA.StackExchange (What are the best practices for triggers to maintain a revision number on records?) has spawned an interesting question (at least, interesting to me) regarding ...
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3answers
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MySQL general query log performance effects

One of our customers who has a somewhat problematic web application would like us to log all the queries for a period of 24 hours. I wouldn't know how much data it will actually write. The amount ...
6
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4answers
8k views

How to improve InnoDB DELETE performance?

So I have this audit table (tracks actions on any table in my database): CREATE TABLE `track_table` ( `id` int(16) unsigned NOT NULL, `userID` smallint(16) unsigned NOT NULL, `tableName` ...
15
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3answers
6k views

Is it common practice to mix InnoDB and MyISAM tables on same server?

I've got a single database of about 4.5GB running on a server with 8GB RAM. The vast majority of the tables are MyIsam (about 4.3GB), but I'm soon going to be converting some of them to InnoDB. (It's ...
2
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1answer
4k views

16 Cores 12 GB RAM server MySql Configuration - my.cnf

The server takes 20+ seconds (wait time/slow IO response time) to response to a HTTP request even with memcached and APC installed. I believe this has something to do with MYSQL since the site as lots ...
14
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1answer
21k 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?
4
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2answers
1k views

How to copy a MySQL database which is a mixture of InnoDB and MyISAM to the same server?

Because mysqldump takes forever, we decided to just move around the files. Because the 2 databases are on the same server, a cp will be fast. The problem is, from research, MyISAM is okay with being ...
4
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3answers
12k views

I've got 16GB of ram, how should I configure MySQL Server?

I've got a dedicated production server with multiple cpus and 16GB of ram. I would like to know how can I configure it better to take advantage of the server resources for better performance because ...
4
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2answers
3k 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 ...
4
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2answers
9k 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, ...
3
votes
3answers
12k views

ERROR Cannot find or open table?

MySQL version: 5.5.24 Due to the following problem: mysql> desc reportingdb.v3_zone_date_cpm7k; ERROR 1146 (42S02): Table 'reportingdb.v3_zone_date_cpm7k' doesn't exist ...
3
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2answers
4k views

LOAD DATA (400k rows) INFILE takes about 7 minutes, cannot kill the “logging slow query” process?

MySQL version: 5.5.13 The query that I'm using: SET AUTOCOMMIT=0; LOAD DATA INFILE '/data10/select_into.outfile/v3_zone_date.out' INTO TABLE v3_zone_date FIELDS TERMINATED BY ','; COMMIT; ...
2
votes
1answer
4k views

Is there a progress indicator for OPTIMIZE TABLE progress?

MySQL 5.1.4x (Windows) | Innodb I recently purged data from a mySQL DB (a few hundred thousand rows) and I'm planning to use OPTIMIZE TABLE LOGTABLEFOO1,LOGTABLEFOO2,LOGTABLEFOO3; to reduce the ...
2
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1answer
296 views

mysql emits BINLOG rows even though binlog_­format=­STATEMENT

We have MySQL 5.5 installed, we have the binlog_format=STATEMENT (the default) According to the MySQL Documentation, the binary log should contain SQL statements only, but we still see BINLOG rows in ...
5
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1answer
3k 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. ...
4
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2answers
6k 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: ...
4
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1answer
2k views

How can I prevent gaps in a MySQL table AUTO_INCREMENT field?

For example, I have a table for user registration: CREATE TABLE IF NOT EXISTS test_user ( user_id int(10) unsigned NOT NULL AUTO_INCREMENT, user_name varchar(50) NOT NULL, PRIMARY KEY ...
4
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3answers
2k views

MySQL tables/databases into different disks

I am aware that there is a possibility to have a single database server with many tables/databases, and you can separate some of those tables/databases into separate disks. Lets say you have 5 ...