MySQL : Open-Source, Relational Database Management System

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3
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1answer
808 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
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
1answer
6k 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 ...
2
votes
1answer
122 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
votes
1answer
274 views

select for update gives error on indexed column

here is my code: mysql_query("start transaction"); $q="select max(id) from test for update"; $r=mysql_query($q); $row=mysql_fetch_array($r); for ($k=0;$k<100000;$k++) { $q="insert into test values ...
2
votes
2answers
385 views

get column from too many tables in mysql

.I have too many tables X1,X2,...Xn (they might exceed 75 tables) in Mysql DB to represent departments of a very large company. every table has structure something like this desc X1; ...
2
votes
1answer
680 views

Understanding mysqltuner Recomendations w/ Unused Catalogs

I have a MySQL 5.0.77 instance running with three catalogs in it. Two of the catalogs contain all InnoDB tables and are actively used. The third is all MyISAM and is basically unused, and is only ...
2
votes
1answer
951 views

LOCK IN SHARE MODE

On dev mysql LOCK IN SHARE MODE is described as... SELECT ... LOCK IN SHARE MODE sets a shared mode lock on the rows read. A shared mode lock enables other sessions to read the rows but not to modify ...
1
vote
2answers
736 views

MySQL Community Edition: Can I replicate my entire server with another server in one go?

I need to migrate all the databases from one server to another. There are about 100 databases, and all databases are used daily and updated/inserted too and read through their respective websites. ...
0
votes
1answer
544 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 ...
11
votes
7answers
9k 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 ...
9
votes
2answers
5k views

MySQL Sharding vs MySQL Cluster

Considering performance only, can a MySQL Cluster beat a custom data sharding MySQL solution? sharding = horizontal partitioning When I refer to sharding, I'm considering sharding made in the ...
8
votes
3answers
13k views

Any better way out of MySQL InnoDB log “in the future”?

I've got this InnoDB error in MySQL 5.0. Mysqld was stopped cleanly, but I managed to lose ib_logfile0 & ib_logfile1 afterward. Now after a clean startup, InnoDB has done its "crash recovery". ...
29
votes
2answers
6k views

NULL or NOT NULL by default?

In MySQL, is it better to always allow nulls unless you know a field is required, or always use Not Null unless you know a field will contain nulls? Or doesn't it matter? I know in some DBMSs they ...
27
votes
9answers
8k views

Is there a tool like Microsoft's “SQL Server Profiler” for MySQL?

While developing on MySQL I really miss being able to fire up a profiler. I find SQLyog is a good enough replacement for Query Analyzer but have not found a tool that works like SQL profiler. For ...
12
votes
4answers
14k views

How do you identify InnoDB table corruption?

I have some tables that are partitioned and have several indexes on a replicated slave. After copying the snap shot (verified safe) to a new slave and upgrading mysqld from 5.1.42 to 5.5.15 and ...
5
votes
3answers
4k views

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
votes
2answers
1k views

MySQL warm procedure

How do you usually warm up your database ? I run a similar queries to this for every table in DB: SELECT * FROM ip_log ORDER BY ID; SELECT ip, member_id FROM ip_log ORDER BY ip, member_id; Is that ...
5
votes
1answer
3k views

Capabilities of InnoDB INSERT Performance

Hi I am running the most recent version of Percona Server. Server version: 5.5.24-55 Percona Server (GPL), Release 26.0 I have a 10 cpu box of these characteristics. processor : 0 vendor_id ...
27
votes
5answers
4k views

When is the right time to use MariaDB instead of MySQL, and Why?

What we earn and what we lost with this migration? What should I expect as drawbacks after the migration? Is it really unnecessary to change the applications in any situation?
12
votes
5answers
5k views

How do I force one record to have a true value for a boolean column, and all others a false value?

I want to enforce that only one record in a table is considered the "default" value for other queries or views that might access that table. Basically, I want to guarantee that this query will always ...
10
votes
1answer
2k views

MySQL table with 100,000 records queried often

I have a single database of about 100 tables to store various kinds of information. The most important table is our order table which is used to store customers orders and is over 100000 records as ...
9
votes
4answers
7k views

Mysql int vs varchar as primary key (InnoDB Storage Engine?

I am build a web application (project management system) and I have been wondering about this when it come to performance. I have an Issues table an inside it there are 12 foreign keys linking to ...
9
votes
1answer
7k views

InnoDB create table error: “Row size too large”

We have some engineers that flatten a normalized db structure into a temporary table for the purposes of generating a report. The columns are specified as TEXT NOT NULL (I know "why are they doing ...
8
votes
2answers
5k 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 ...
6
votes
2answers
28k 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
3answers
5k 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 ...
4
votes
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? ...
2
votes
2answers
4k views

Reset MySQL root password in LAMPP server on Ubuntu

I forgot the password I changed for the root user of MySQL. I'm logged in as root user and when I do # /opt/lampp/lampp security it gives result as XAMPP: Quick security check... XAMPP: Your XAMPP ...
20
votes
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 ...
4
votes
2answers
6k 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
1answer
747 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
votes
2answers
944 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 ...
1
vote
2answers
128 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' ...
1
vote
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 ...
14
votes
5answers
6k views

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? ...
12
votes
1answer
13k 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?
6
votes
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
votes
1answer
731 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
votes
2answers
937 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
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
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
votes
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 ...
3
votes
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 ...
3
votes
2answers
1k 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 ...
2
votes
1answer
2k 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
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 ...
6
votes
4answers
2k 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
2answers
312 views

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
votes
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 ...