MySQL : Open-Source, Relational Database Management System

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2answers
789 views

How do I determine how much data is being written per day through insert, update and delete operations?

The longevity of SSDs is largely determined by the amount of bytes written by insert, update and delete operations. What is the best way to accurately determine how much data is being written by ...
2
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2answers
801 views

Which first: upgrade mysql version or convert storage engine?

I inherited a production mysql server at 5.0. It uses MyISAM exclusively. It is not a high volume database but it does have some large datasets. I am planning on: upgrading to 5.5 converting ...
55
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5answers
4k views

How can a group track database schema changes?

What version control methodologies help teams of people track database schema changes?
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7answers
14k views

Get the rank of a user in a score table

I have a very simple MySQL table where I save highscores. It looks like that: Id Name Score So far so good. The question is: How do I get what's a users rank? For example, I have a users ...
10
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3answers
11k views

Why is 'LOAD DATA INFILE' faster than normal INSERT statements?

I've read an article that mentioned we can achieve 60,000 inserts per second by LOAD DATA IN FILE statement that read from csv files and insert it into database. Why should it differ from normal ...
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8answers
9k views

Tool to generate large datasets of test data [closed]

Many times when trying to come up with an efficient database design the best course of action is to build two sample databases, fill them with data, and run some queries against them to see which one ...
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3answers
18k views

Is it safe to use innodb_flush_log_at_trx_commit = 2

I turned innodb_flush_log_at_trx_commit = 2 and get a very fast write speed. But is it safe be used in production web site?
20
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1answer
21k views

intermittent MySQL crashes with error “Fatal error: cannot allocate memory for the buffer pool”

Added on edit, 2013-05-29: Because this is a long question and discussion, here's a short summary of the question and the solution. I had problems running MySQL and Apache on a small Linux server (1 ...
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7answers
16k views

Is it possible to mysqldump a subset of a database required to reproduce a query?

Background I would like to provide the subset of my database required to reproduce a select query. My goal is to make my computational workflow reproducible (as in reproducible research). Question ...
5
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1answer
3k views

Best solution for cross-datacenter MySQL master-slave replication

We are working on a new system architecture for our company. We have a HPC, which runs in our own data-center and we are planning our front-end and a fallback system on Amazon Web Service. System ...
6
votes
1answer
2k views

How large will a MySQL database be relative to the dump file?

I'm restoring a ~52GB dump to a MySQL database. The ibdata1 file has already exceeded the size of the dump file and the restore is still incomplete. Is there any way to estimate the final size of the ...
6
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1answer
3k views

MySQL Workbench Database Sizes

I'm trying to find the total size on the hard disk that all of my MySQL Workbench databases are using. Does anyone know of an easy way to figure this out? If nothing else, the default location ...
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4answers
3k views

MySQL Replication - Introduce new Slave to replication

I've recently taken on a sys admin position managing a group of 20 (or so) servers. One thing I haven't dealt with before (apart from in a test situation), is introducing a new slave to the MySQL ...
3
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1answer
4k views

Fixing tables out of sync as reported by pt-table-checksum, pt-table-sync is not working

I have several tables being reported by pt-table-checksum with CRC_DIFF between my master and slave servers using the following commands: $ pt-table-checksum h=master,u=user,p=password ...
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4answers
3k views

One slave, multiple masters MySql

Is it possible to set-up MySql Replication to have one slave listening to two different masters?
6
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2answers
7k views

InnoDB: Error: Table “mysql”.“innodb_table_stats” not found after upgrade to mysql 5.6

I upgraded to mysql 5.6 from 5.5, and now my logs are littered with such messages on startup I found a possible solution here, but it does not seem official. ...
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 ...
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4answers
3k views

Is raid 5 suitable for a mysql installation?

Is raid 5 suitable for a mysql installation? Let me explain my application further. My application is a socket programming which will connect with gps device to receive gps string and there after do ...
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3answers
4k 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 ...
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2answers
656 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?
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5answers
2k 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 ...
5
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1answer
1k views

MySQL Replication : 1 Slave / Multiple Masters

I have a web app with 2 web servers and 2 database servers. The DBs are setup for multimaster replication. (this is the primary environment) I also have the exact same setup on a different location ...
4
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1answer
968 views

How does max_allowed_packet affect the backup and restore of a database?

I have a database based on mysql 5.0.75-0Ubuntu10.2, running under Ubuntu 9.04. I have a table in that database with a medium blob column. I have been using automysqlbackup to do nightly backups/dumps ...
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3answers
4k 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 ...
3
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1answer
932 views

FULLTEXT index ignored in BOOLEAN MODE with 'number of words' conditional

fulltext match is ignoring its index when I add a number of words conditional for its boolean mode. The selects are as follows: explain select * from seeds WHERE MATCH(text) AGAINST ("mount ...
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
515 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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1answer
6k 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) ...
2
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1answer
1k 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 ...
2
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1answer
135 views

Combining columns in index

With reference to RolandoMySQLDBA's answer on MySQL: Index when joining to tables not being used (Performance optimizing question) He mentioned Make sure you build an index that involves the ...
2
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1answer
705 views

Create a custom log table in MySQL

Is it possible to create a custom log table. For example I have 10 schema and I would like to log if somebody is using the "areva" schema. I want to know the last executed command time and the user. ...
2
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1answer
723 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 ...
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4answers
4k 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?
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1answer
624 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
734 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
740 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 ...
0
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1answer
653 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 ...
180
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15answers
65k 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 ...
4
votes
1answer
6k 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
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innodb_file_format Barracuda

I have a couple questions for those more familiar. Most of my instances have been running Antelope despite having support for Barracuda. I was looking to play around with some compresses innodb ...
7
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2answers
4k 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 ...
5
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1answer
2k views

Qcache_free_memory not full yet I get alot of Qcache_lowmem_prunes

I just started dabbling with the query cache for our CMS. Can anyone tell me (or at least give a good guess) why I get a lot of Qcache_lowmem_prunes when more than half of Qcache_free_memory is free? ...
9
votes
3answers
2k views

How is LIKE implemented?

Can anyone explain how the LIKE operator is implemented in current database systems (e.g. MySQL or Postgres)? or point me to some references that explain it? The naive approach would be to inspect ...
7
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3answers
12k 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 ...
14
votes
3answers
5k 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 ...
9
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3answers
6k views

What is the default order of records for a SELECT statement in MySQL?

Suppose you have the following table and data: create table t(k int, v int,index k(k)) engine=memory; insert into t values(10, 1), (10, 2), (10, 3); When issuing select * from t where k = 10 with ...
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3answers
6k views

InnoDB table SELECT returns ERROR 2006 (HY000): MySQL server has gone away (after power outage)

This server is a virtual machine running CentOS 6.0, MySQL 5.5.21 There is a database named devSystem. There are InnoDB tables within. Running the following commands causes error ERROR 2006 ...
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4answers
7k 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` ...
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2answers
6k views

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 ...