Questions tagged [myisam]

MyISAM is the non-transactional storage engine for MySQL. It provides high-speed storage and retrieval, as well as fulltext searching capabilities. In addition, it is the default storage engine type for versions of MySQL prior to 5.5.

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250
votes
10answers
248k views

What are the main differences between InnoDB and MyISAM?

What are the main differences between InnoDB and MyISAM?
106
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5answers
180k views

How to safely change MySQL innodb variable 'innodb_log_file_size'?

So I'm fairly new to tuning InnoDB. I'm slowly changing tables (where necessary) from MyIsam to InnoDB. I've got about 100MB in innodb, so I increased the innodb_buffer_pool_size variable to 128MB: ...
56
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4answers
116k views

Which is faster, InnoDB or MyISAM?

How can MyISAM be "faster" than InnoDB if MyISAM needs to do disk reads for the data? InnoDB uses the buffer pool for indexes and data, and MyISAM just for the index?
55
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3answers
67k views

Why does InnoDB store all databases in one file?

It was convenient that MyISAM used to store each table in a corresponding file. InnoDB has made advancements in many aspects, but I wonder why InnoDB stores all databases in one file (ibdata1 by ...
36
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4answers
14k 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 ...
34
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5answers
47k views

Why are simple SELECTs on InnoDB 100x slower than on MyISAM?

I have quite an annoying problem. I want to use INNODB as my main database engine and give up on MyISAM as I need the former for using galera-cluster for redundancy. I copied (description follows) ...
33
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6answers
87k views

How to update 10 million+ rows in MySQL single table as Fast as possible?

Using MySQL 5.6 with InnoDB storage engine for most of the tables. InnoDB buffer pool size is 15 GB and Innodb DB + indexes are around 10 GB. Server has 32GB RAM and is running Cent OS 7 x64. I have ...
28
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3answers
18k 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 ...
28
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3answers
43k views

How can I change the default storage engine in phpmyadmin?

I use InnoDB almost exclusively in my applications. However, if I'm not careful when setting up the table, I forget to change it and phpmyadmin sticks me with MyISAM. Is there a way to change the ...
22
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6answers
40k views

DELETE command not completing on 30,000,000 row table

I have inherited a database and am looking to clean and speed it up. I have a table that contains 30,000,000 rows, many of which are junk data inserted due to an error on behalf of our programmer. ...
22
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3answers
9k views

Is the overhead of frequent query cache invalidation ever worth it?

I'm currently working on a MySQL database where we are seeing a large number of invalidations from the query cache, primarily because of the high number of INSERT, DELETE and UPDATE statements that ...
21
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3answers
16k 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 ...
20
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1answer
15k views

Does mysqldump export indices, by default?

I played around a little with mysqldump and I was wondering, if it does export indices (FULLTEXT, INDEX,...) by default. I read up on it and I found this option: --disable-keys, -K which suggests, ...
17
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3answers
16k views

Best of MyISAM and InnoDB

Is it possible to make InnoDB to use indexes same as MyISAM instead of clustered index due to limitation of RAM while getting benefit of its concurrency performance?
16
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2answers
4k views

Rows missing after online conversion from MyISAM to InnoDB

We have a reasonably small database that we wanted to convert from MyISAM to InnoDB. Being database noobs, we just converted (using alter table) without even taking the site down. Now that the ...
15
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2answers
43k views

MySQL performance problem using indexed datetime column

I tried to solve the following problem for about one hour now and still didn't get any further with it. Okay, I have a table (MyISAM): +---------+-------------+------+-----+-------------------+-----...
14
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4answers
24k views

MySQL LOAD DATA INFILE slows by 80% after a few gigs of input with InnoDB engine

I'm loading a 100GB file via LOAD DATA INFILE. I've had good success with MyISAM, a few hours and done. I'm trying it now using InnoDB. The load starts fast at over 10MB/sec (watching the table file ...
13
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1answer
9k views

MySQL command querying all MyISAM database

I would appreciate if anyone could help me of what's the proper command in MySQL to query all database for having "MyISAM" engine. I need to convert all DB & tables from MyISAM to InnoDB.
13
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5answers
4k 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 ...
13
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2answers
30k views

Why is MySQL is creating so many temporary tables on disk?

Can any configuration mistake lead to creating too many temp tables by mysql..mysql tuner shows Current max_heap_table_size = 200 M Current tmp_table_size = 200 M Of 17158 temp tables, 30% were ...
12
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3answers
3k views

MySQL instance stalling “doing SYNC index”

Problem An instance of MySQL 5.6.20 running (mostly just) a database with InnoDB tables is exhibiting occasional stalls for all update operations for the duration of 1-4 minutes with all INSERT, ...
11
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2answers
9k views

How to drop empty tables

Is it possible to drop all empty tables from my huge database (mysql)? I'm looking for a sql command to automatically remove all those empty tables. Currently, I have 305 tables in my dataset, and ...
11
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1answer
9k 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 ...
11
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2answers
6k 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 ...
10
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5answers
52k views

How to determine the optimal sort_buffer_size?

I read from a sample configuration file which says the following: # Sort buffer is used to perform sorts for some ORDER BY and GROUP BY # queries. If sorted data does not fit into the sort buffer, a ...
10
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2answers
62k views

way to prevent queries from waiting for table level lock

We've encountered a problem after moving the database of our customer to an extra server. This should have had positive effects on the site's performance, but there is a problem with table locking in ...
10
votes
1answer
12k views

Why full-text-search returns less rows than LIKE

I don't get full-text-search working as I want it to, and I don't understand the differences in the resultlists. Example statements: SELECT `meldungstext` FROM `artikel` WHERE `meldungstext` LIKE '%...
10
votes
2answers
20k views

Using multiple cores for single MySQL queries on Debian

I am running a MySQL server for tests on a VM (VMWare) with Debian as guest OS. The guest has four emulated CPU cores, so I set thread_concurrency to four. I am doing expensive joins on large tables, ...
10
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4answers
32k views

How to increase fast backup and restore of 500GB database using mysqldump?

There is a database A size of 500GB. Tables in database A contains both MyISAM and INNODB tables. MyISAM tables are master tables and Innodb tables are main transaction tables. Backup and restore ...
10
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1answer
3k views

recover a single mysql database on a busy master-slave replicated system

Looking for a strategy or tool to deal with recovering a single database to a point-in-time in a busy replicated system. I have 12 databases running on 2 MySQL 5.0.77 servers in master-slave ...
9
votes
5answers
30k views

Mysql: Insert performance INNODB vs MYISAM

I am inserting into a simple small table with 5 attributes and 1000 rows. I observed when the engine is INNODB, each insert is taking 0.03 - 0.05 seconds. I changed the engine to MYISAM, then the ...
9
votes
4answers
26k views

Why does MySQL produce so many temporary MYD files?

On a Debian Linux server, hosting many PHP/MySQL websites (photo galleries), sometimes I have "many" files like /tmp/#sql_6405_58.MYD. For example today : [2012-12-15 15:18:11] /tmp/#sql_6405_6.MYD :...
9
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3answers
30k 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 ...
8
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1answer
1k views

Does MySQL still handle indexes in this way?

Dropping a duplicate index in MySQL was taking rather long, so while I was waiting I searched about it & found this post from 2006, talking about how MySQL handles ADD and DROP index. If a ...
8
votes
2answers
909 views

Why would MySQL do serial synchronous I/O?

When looking at a particularly annoying query over MyISAM tables which takes a long time to execute on a number of occasions, I have noted that MySQL seems to expose a rather strange I/O pattern: when ...
8
votes
1answer
3k 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?
8
votes
1answer
10k views

Do you still use MyISAM or prefer Aria storage engine?

If Aria storage engine (previously called Maria) is the "new" MyISAM, which supports transaction and automatic crash recovery: Why still use MyISAM ? Should changing storage engine from MyISAM to ...
8
votes
2answers
3k views

Insert-heavy InnoDB table won't use all my CPU

I have a packet log database, which is almost never queried. It just needs to be fast on inserts. I'm using InnoDB because I'd like to maintain ACID compliance, since even losing a single packet could ...
8
votes
2answers
9k views

Consistent logical backup of databases that use MyISAM and InnoDB engines

I have a question regarding the logical backup of MySQL databases that use both MyISAM and InnoDB. The mysqldump utility supports these two options: --single-transaction - Creates a consistent ...
8
votes
1answer
56k views

What is causing Waiting for table level lock errors?

We got the database hanging twice already and trying to find a cause. show processlist Waiting for global read lock | INSERT INTO {myisam_table} ... In here the disk space was full so we thought ...
8
votes
2answers
17k views

Optimizing WHERE condition for TIMESTAMP field in MySQL SELECT statement

I am working on a schema for an analytics system which tracks usage times, and there is a need to see total usage time in a certain date range. To give a simple example, this type of query would be ...
8
votes
1answer
722 views

Start/Stop MySQL

I'm seeking help to understand what happens when the following command line is executed: root@prodn$ service mysqld stop Yes, it shuts down the MySQL server so access to it is no longer available ...
7
votes
6answers
17k views

TRUNCATE TABLE statement sometimes hangs

Why does the TRUNCATE TABLE statement hang sometimes? What are the reasons for this type of issue? I am migrating from MySQL to MariaDB. This problem doesn't happen with MySQL, only with MariaDB. ...
7
votes
4answers
7k 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 ...
7
votes
3answers
7k views

How much memory will a MEMORY table take up?

Let's say I have a MyISAM table with a data length of 4.8GB and an index length of 6.2GB. So, a total data size of eleven gig. How much memory would this require, were I to convert it to a MEMORY ...
7
votes
4answers
13k views

mysql insert into indexed table taking long time after few million records

I have a table like this CREATE TABLE IF NOT EXISTS `dnddata` ( `numbers` varchar(10) NOT NULL, `opstype` char(1) NOT NULL, PRIMARY KEY (`numbers`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 /*!...
7
votes
1answer
7k 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 ...
7
votes
1answer
6k views

MySQL 5.1 to 5.6: massive performance hit

Okay, this is possibly three questions. I want to move my existing MySQL 5.1 database using MyISAM to 5.6 using InnoDB for what I think are a host of obvious -- and possibly even good -- reasons. ...
7
votes
1answer
6k views

Is Percona xtrabackup the right choice for my 500GB MySQL backup?

I have a MySQL db with 500GB, consisting mainly of Innodb tables, and one big (200GB) MyISAM table. My current backup strategy is copying the db files to an external harddrive. This causes a downtime ...
7
votes
1answer
7k views

Setting up replication for MyISAM tables?

Before setting up a replication within MySQL, the data first needs to be transferred to the slave. Since MyISAM tables can be copied as files. Would it be okay to copy MyISAM files, .myd .myi .frm, ...

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