MySQL : Open-Source, Relational Database Management System

learn more… | top users | synonyms

1
vote
1answer
723 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
vote
1answer
799 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
vote
1answer
812 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 ...
188
votes
15answers
72k 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 ...
9
votes
3answers
13k 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 ...
5
votes
1answer
7k 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 ...
8
votes
5answers
15k views

Fastest way to check if InnoDB table has changed

My application is very database intensive. Currently, I'm running MySQL 5.5.19 and using MyISAM, but I'm in the process of migrating to InnoDB. The only problem left is checksum performance. My ...
7
votes
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 ...
6
votes
2answers
11k 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 ...
6
votes
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` ...
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 ...
7
votes
3answers
47k views

MySQL: how to restore table stored in a .frm and a .ibd file?

I have previously saved a copy of /var/lib/mysql/ddms directory ("ddms" is the schema name). Now I installed a new MySQL on a freshly installed Ubuntu 10.04.3 LTS by running apt-get install ...
7
votes
3answers
7k 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 ...
2
votes
1answer
3k 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 ...
13
votes
1answer
17k 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?
8
votes
2answers
6k views

For absolute performance, is SUM faster or COUNT?

This relates to counting the number of records that match a certain condition, e.g. invoice amount > $100. I tend to prefer COUNT(CASE WHEN invoice_amount > 100 THEN 1 END) However, this is ...
4
votes
3answers
10k 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
votes
2answers
6k views

MySQL Event does not run

i am running mysql 5.1.41 that came bundled with xampp on windows. the problem is that the event doesnt run automatically even when the event scheduler is ON. i have a table named ta_table using ...
3
votes
2answers
1k 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
votes
1answer
3k 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
votes
1answer
279 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
votes
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?
4
votes
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
votes
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
votes
3answers
2k views

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 ...
4
votes
2answers
1k views

Select rows where value of second column is not present in first column

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
votes
1answer
1k 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
votes
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 ...
4
votes
1answer
3k views

Can I rename the values in a MySQL ENUM column in one query?

Suppose I have a Database table with an ENUM('value_one','value_two'). I want to change that to an ENUM('First value','Second value'). I an currently doing that as follows: ALTER TABLE `table` MODIFY ...
4
votes
4answers
1k views

Is it feasible to have MySQL in-memory storage engine utilize 512 GB of RAM?

I am considering scaling up instead of scaling out. Therefore, I am interested to hear whether it is feasible to utilize the MySQL in-memory storage engine for a database that is 500+ GB, given that ...
3
votes
4answers
4k 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
votes
1answer
412 views

Limiting database security

A number of texts signify that the most important aspects offered by a DBMS are availability, integrity and secrecy. As part of a homework assignment I have been tasked with mentioning attacks which ...
3
votes
1answer
2k views

MySQL Server Performance

I have a few questions regarding MySQL server running under Windows Server 2008 R2: How do I check the number of allowed connections? How do I turn on query logging to see performance of queries ...
2
votes
2answers
215 views

MySQL 5.6 showing wrong “second_behind_master”

mysql> show slave status\G *************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 10.10.7.98 ...
2
votes
1answer
301 views

optimal table design mysql with primay key and varchar value

I have a table: id (PRIMARY KEY AUTO_INCREMENT) value (UNIQUE KEY) which currently holds over 50 millions rows (and growing fast) and is hit hard: process 1 queries this table (>200/sec) with a ...
2
votes
2answers
253 views

MySql - find redundant indexes

is there a tool that spots redundant indexes in MySql? e.g. if I have the following indexes: index1(col1) index2(col1,col2) then index1 should be flagged as redundant. any ideas?
6
votes
4answers
3k views

MySQL InnoDB locks primary key on delete even in READ COMMITTED

Preface Our application runs several threads that execute DELETE queries in parallel. The queries affect isolated data, i.e. there should be no possibility that concurrent DELETE occurs on the same ...
6
votes
4answers
6k views

MySQL gives “Out of Memory” error when inserting a large file. From where is this filesize limitation arising?

I'm using a MySQL database to store files. The table I'm using is structured as follows: +--------------+----------+------+-----+---------+-------+ | Field | Type | Null | Key | Default ...
5
votes
3answers
6k views

Maximum table size for MySQL database server running on Windows (NTFS) Table type InnoDB

I need to design database to store information contained in millions of log files generated by devices on trial on network. I have designed 5 different tables to store log file information. But, as ...
5
votes
1answer
721 views

will replication from 5.5.20 to 5.0.XX server work?

I gave two machines which run on two entire different versions of MySQL server. I want to do the replication from 5.5.20 to 5.0 server. Will that be possible? Because I remember when I transferred ...
4
votes
1answer
1k views

Which mysql storage engine to choose?

I'm confused about which mysql engine should I choose (lets talk about the most used : MyISAM and InnoDB). The theories say: Both work with BTree indexes, but MyISAM can work with FULLTEXT index ...
4
votes
2answers
724 views

How to resolve the master server shut down/unavailability in mysql with master - slave replication

Let us suppose that we have a master/slave setup and the application is running fine for the time being. All of a sudden the master server suddenly shuts down due to some problem. Now how can I ...
4
votes
2answers
672 views

Less RAM than Index_length MyISAM

I'm working on a database to store "time series" data (the value of X was Y at this time). The rows themselves are very small and static in size, with the primary key consisting of two smallint ...
4
votes
3answers
836 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
votes
1answer
760 views

What are your use-cases for HandlerSocket?

There's a bit of hype around: HandlerSocket It seems like faster, nosql access to MySQL data is becoming more desirable. Percona Server is now shipping with HandlerSocket built in. My question is, ...
3
votes
1answer
2k views

MySQL Slave Relay Logging but not logging Binary Log

I have a master slave setup both mysql 5.5, the setup is fine except that the slave won't Binary log to the standard mysql-binlog only to the relay logs. I fear this may be due to my lack of ...
3
votes
1answer
472 views

Setting up MySQL circular replication in existing replication topology?

I have the following MySQL replication topology set up for fault tolerance/disaster recovery with master server A and slaves B and C: A replicates to B A replicates to C Both B and C are fully up ...
3
votes
2answers
5k 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
votes
1answer
3k views

Can we capture only Slave_IO_Running in SHOW SLAVE STATUS in MySQL

I wanted to capture only status/result of Slave_IO_Running and Slave_SQL_Running column values, which I will be using to integrate into our application. Is there any way to get only the values of ...
2
votes
1answer
65 views

How can I determine which Innodb table is being written?

I am running Mysql 5.5. I have about 100 Innodb tables spread over 10 DB's (mostly wordpress sites) and I am recently seeing a lot more disk IO than I have been, without any increase in traffic. The ...