All versions of MySQL (not Microsoft SQL Server). Please also add a version-specific tag like mysql-5.7 if that is relevant to the question.

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12
votes
4answers
24k views

Modify DEFINER on Many Views

I have am having problems backing up my databases after an update. I have been poking around on my system trying to figure out why. One query I ran returned this result. Got error: 1449: The user ...
14
votes
3answers
11k views

Why query_cache_type is disabled by default start from MySQL 5.6?

We've upgraded to MySQL 5.6 and start seeing the loading of db server increased significantly, and finally found out the query_cache_type is defaulted to off start from 5.6. We enabled it again and ...
11
votes
2answers
3k views

Must an index cover all selected columns for it to be used for ORDER BY?

Over at SO, someone recently asked Why isn't ORDER BY using the index? The situation involved a simple InnoDB table in MySQL comprising three columns and 10k rows. One of the columns, an integer, ...
6
votes
4answers
27k views

Cannot GRANT privileges as root

Because of having some problems, I decided to re-create all users except for root@localhost. This works fine, but the newly created user has no right to do anything. What I want is to simply give all ...
13
votes
2answers
26k views

How to solve “The table … is full” with “innodb_file_per_table”?

I have a MySQL database that holds a large amount of data (100-200GB - a bunch of scientific measurements). The vast majority of the data is stored in one table Sample. Now I'm creating a slave ...
7
votes
2answers
10k views

How can you have two auto-incremental columns in one table?

I have a MySQL table that contains information on invoices of a company. However, this company has two branches, and each of them has a unique invoicing sequence; a "Serie A" and "Serie B", so to ...
8
votes
3answers
3k views

Is MySQL Replication Affected by a High-Latency Interconnect?

We've got a vanilla master and slave MySQL setup that reside in different data centers, and another slave in the same datacenter as the master. The bandwidth between the datacenter is pretty high (in ...
5
votes
2answers
4k views

Setting Circular Replication in mysql

I have 3 MySQL servers say A,B,C. What I want to do is that I want to make all of them master as well as slave.If there is update on any of the MySQL Servers it should be replicated to all of the ...
4
votes
5answers
4k 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 ...
4
votes
1answer
6k views

Mysql fulltext search my.cnf optimization

I have open a question on http://serverfault.com/questions/353888/mysql-full-text-search-cause-high-usage-cpu Some user recommended asking here. We built a news site. Every day we will input tens of ...
62
votes
4answers
11k views

Storing vs calculating aggregate values

Are there any guidelines or rules of thumb to determine when to store aggregate values and when to calculate them on the fly? For example, suppose I have widgets which users can rate (see schema ...
8
votes
2answers
28k views

How do you remove fragmentation from InnoDB tables?

I have a Database having number of tables. I want to delete some records from the tables say the no of records are more than 20K or 50K. The All the Tables are InnoDB. And file_per_table is off. ...
4
votes
2answers
10k views

Local database vs Amazon RDS

I am doing large INSERT into a local MySQL database I am at 2,000,000 rows and am really starting to notice the slowdown now. I always heard that MySQL wasn't very scalable I expect this database to ...
7
votes
1answer
6k views

When to switch from MyISAM to InnoDB?

We have a MySQL 5.0 server running all tables as MyISAM. We have two slaves that, in the last month, we have upgraded to MySQL 5.5. Their tables are also still MyISAM. My original plan was to upgrade ...
2
votes
2answers
23k views

MySql - Clean ibdata1

I have a database that its entire size is ~44GB, out of it ibdata1 is ~35GB that doesnt make sense, the size of the data shouldnt be more then 10GB. i use the following query to get an esstimation of ...
14
votes
2answers
13k 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
1answer
494 views

How badly does innodb fragment in the face of somewhat out-of-order insertions?

Let's say there's a composite primary key on (field1, field2) Also, let be X a theoretical set of n numbers Inserts look like this: INSERT INTO table(field1, field2) VALUES([a number picked at ...
15
votes
3answers
16k views

check constraint does not work?

I have the following table. create table test ( id smallint unsigned AUTO_INCREMENT, age tinyint not null, primary key(id), check (age<20) ); The problem is that the CHECK ...
2
votes
3answers
1k views

MySql shell command not replicated to slave

I have a shell script that looks something like that: #!/bin/bash mysql -udb_user -pdb_password -e "LOAD DATA LOCAL INFILE '/srv/some_file.csv' INTO TABLE db_name.db_table FIELDS TERMINATED BY ...
8
votes
1answer
4k 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 ...
3
votes
3answers
2k views

Restoring an old backup to latest MySQL release

Our old database is MySQL 5.1 server and is four years old. If I uninstall MySQL 5.1 Server and install the latest release and restore the backup, will I gain performance benefits? I guess the new ...
3
votes
1answer
1k views

MySQL InnoDB data file directly on a disk slice (fixed-size)?

It seems that ibdata1 is like a disk slice. In Solaris (UNIX) UFS filesystems (the common one before ZFS), one would separate their disk c0t0d0 into slices, say a 10GB drive would be cut into three ...
7
votes
4answers
5k views

Benefits of table level locking

What are the benefits of table level locking which is used by the MyISAM storage engine? Row level locking has lots of benefits like concurrent updates and reads that do not lock the table. Edit Its ...
2
votes
3answers
708 views

mysql replication master 5.5 slave 5.1 error on create database

I have a replication system where my master has a mysql 5.5 version while the slave is mysql 5.1. I know that this is not supported because the slave version should be greater than the master, but we ...
20
votes
7answers
41k 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 ...
33
votes
1answer
45k 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 ...
21
votes
3answers
9k views

How Does Table Partitioning Help?

I am having difficulty to grab the idea of pros and cons of table partitioning. I am about to start work on a project which would have 8 tables and one of them will be the main data table which will ...
13
votes
4answers
91k 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 ...
6
votes
1answer
13k views

Best way to setup master to multi master replication

ORIGINAL QUESTION: I have multiple servers that all need to act as masters, as if one fails the next server kicks in and takes over. I'm just wondering what the best way to replicate is. All servers ...
6
votes
2answers
4k views

Scaling Percona datacenters: setup and replication

Since our startup has taken off nicely we are now meeting with some of those issues that you always assumed would NEVER effect you. We have already scaled alot of our application stack: we offloaded ...
12
votes
3answers
12k views

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 ...
10
votes
3answers
12k views

Why does MySQL ignore the index even on force for this order by?

I run an EXPLAIN: mysql> explain select last_name from employees order by last_name; +----+-------------+-----------+------+---------------+------+---------+------+-------+----------------+ | ...
10
votes
3answers
4k views

Dynamic SQL in MySQL stored routines

According to the restrictions on stored routines and triggers, dynamic sql cannot be used (restriction lifted for stored procedures in version 5.0.13 and later). Why is this limitation in place? And ...
5
votes
2answers
4k views

Running multiple instances on the same host

I need to set up multiple MySQL instances on the same host for one of our customers. As far as I see I could go with: mysqld_multi MySQL Sandbox This should be a long term solution for an ...
12
votes
2answers
3k views

Is there an execution difference between a JOIN condition and a WHERE condition?

Is there a performance difference between these two example queries? Query 1: select count(*) from table1 a join table2 b on b.key_col=a.key_col where b.tag = 'Y' Query 2; select ...
11
votes
1answer
6k views

Cannot drop anonymous user from mysql.user

I am trying to DROP the anonymous users from my mysql.users database. However, I have been getting odd behavior. When I enter the command: DROP User ''@'WOPR'; I was getting a generic error ...
5
votes
2answers
6k views

Scheduled optimization of tables in MySQL InnoDB

What is the best way to schedule automatic optimization of tables in a MySQL InnoDB database? Can I use events for example? I have recently had a big performance issue (when querying) with one of the ...
6
votes
3answers
4k views

Changed max_allowed_packet and still receiving 'Packet Too Large' error

I use mysqldump to create a flat file for backup purposes. I have used this file to recreate the database on an alternate server. I ran the import process through ssh on the command line and I ...
5
votes
1answer
1k views

MySQL EXPLAIN doesn't show 'use index' for FULLTEXT

I have a basic table : create table fullTextTest ( id INT(11) NOT NULL, superText CHAR(255) NOT NULL, superLongText TEXT NOT NULL, primary key (`id`), FULLTEXT KEY `superText` ...
4
votes
1answer
1k 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 ...
3
votes
1answer
159 views

Constrains relationship

I have the following design. Each user has it's own contacts, it's own hosts and assign those to a domain which belongs only to him. I want to insure that the host you assign to the domain belongs ...
2
votes
1answer
8k views

How to enable MySQL general log?

I would like to enable the MySQL General Log to view all the (slow) queries. I'm using XAMPP as server and have no idea how to enable it. I can't find a good guide on the internet. Can someone help ...
58
votes
3answers
32k views

Advantages and Disadvantages to using ENUM vs Integer types?

Lets say in some random table, you have a column named status. It's real-world values would be either enabled or disabled. Is it better for this column's data type to be an int/bool (1 or zero) or to ...
37
votes
4answers
39k 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?
16
votes
7answers
33k 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 ...
11
votes
3answers
19k 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 ...
10
votes
2answers
14k views

What to set innodb_buffer_pool and why..?

I have 170GB of InnoDB index and Data. I have to readjust the innodb_buffer_pool size for better performance.The Max table size of a InnoDB table(Index+data) is 28GB. So what should be the optimal ...
17
votes
2answers
27k 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. ...
10
votes
3answers
21k 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 ...
8
votes
2answers
4k views

Any gotchas at all with converting from MyISAM to InnoDB?

I'm ready to move from MyISAM to InnoDB but wanted to know if there was a full list of things to look for? For example, I haven't seen any list mention that running DISABLE KEYS on an InnoDB table ...