How can I reduce the size of MySQL database?

How can I reduce the size of MySQL database?

OPTIMIZE TABLE reorganizes the physical storage of table data and associated index data, to reduce storage space and improve I/O efficiency when accessing the table. The exact changes made to each table depending on the storage engine used by that table.

What causes a surge in write activity in MySQL?

For example, creating a new MySQL instance and its associated data files could cause large surges of disk write activity, impeding the performance of other MySQL instances that use the same storage devices. Configuring a threshold helps avoid such surges in write activity.

What to do if you drop a table in MySQL?

If you drop some tables and delete some data, then there are two ways to reclaim that unused disk: Change the storage engine and revert it back to your previous configuration. This will definitively recreate the table and indexes from the start and unused disk space will be reclaimed.

What’s the best way to backup MySQL database?

Best practices suggest to backup your database before take any dangerous action. MySQL and MariaDB include the mysqldump utility to simplify the process to create a backup of a database or system of databases. If you are using MariaDB, you have the option of full or incremental backup via mariabackup utility.

Is there a way to split the output from MySQL?

I can only upload (compressed) sql files smaller than 2MB. But the compressed output from a mysqldump of the first database’s tables is larger than 10MB. Is there a way to split the output from mysqldump into smaller files? I cannot use split (1) since I cannot cat (1) the files back on the remote server. Or is there another solution I have missed?

How to split MySQL dump into multiple dumps?

Also once you extract single table which you think is still bigger, you can use linux split command with number of lines to further split the dump. split -l 10000 filename.sql That said, if that is your need (coming more often), you might consider using mydumper which actually creates individual dumps you wont need to split!

Is there a limit to the number of tables in MySQL?

MySQL has no limit on the number of tables. The underlying file system may have a limit on the number of files that represent tables. Individual storage engines may impose engine-specific constraints. InnoDB permits up to 4 billion tables.

Which is the most interesting table in MySQL?

The TABLE_STATISTICS and INDEX_STATISTICS are the most interesting tables. The first table shows the number of rows reads from the table and the number of rows changed in the table. The second table shows statistics on index usage. With the help of the new tables, you can find all unused indexes in a single query.

Is it possible to shrink a database to 10 MB?

For example, if a database was originally created with a size of 10 MB and grew to 100 MB, the smallest size the database could be reduced to is 10 MB, even if all the data in the database has been deleted. You cannot shrink a database while the database is being backed up.

Why is it important to reduce the size of a database?

Even though size reduction is rarely the primary objectives of such projects, reducing the size often helps to achieve other goals. Think about designing Disaster Recovery (DR) strategy. Plenty of things that can help to meet strict RTO requirements and smaller database size definitely helps.

What happens when you shrink a SQL Server database?

If you shrink a database repeatedly and notice that the database size grows again, this indicates that the space that was shrunk is required for regular operations. In these cases, repeatedly shrinking the database is a wasted operation.

How to drop index from table in MySQL?

DROP INDEX drops the index named index_name from the table tbl_name. This statement is mapped to an ALTER TABLE statement to drop the index. See Section 13.1.8, “ALTER TABLE Statement” .

What’s the best way to rebuild a table in MySQL?

Dump and Reload Method If you are rebuilding tables because a different version of MySQL cannot handle them after a binary (in-place) upgrade or downgrade, you must use the dump-and-reload method. Dump the tables before upgrading or downgrading using your original version of MySQL. Then reload the tables after upgrading or downgrading.

How to drop an index from a table in NDB?

DROP INDEX drops the index named index_name from the table tbl_name. This statement is mapped to an ALTER TABLE statement to drop the index. See Section 13.1.8, “ALTER TABLE Syntax” . Indexes on variable-width columns of NDB tables are dropped online; that is, without any table copying. The table is not locked against access from other NDB…

How to change the data type for a column in MySQL?

I want to change the data type of multiple columns from float to int. What is the simplest way to do this? There is no data to worry about, yet. Depending on how many columns you wish to modify it might be best to generate a script, or use some kind of mysql client GUI

How big of an object can be stored in MySQL?

This type can store up to 255 bytes (expressed as 2^8 -1) or 255 characters and requires a 1 byte overhead. This object can be used to store things like short summaries, URL links, and other shorter objects.

Which is mysql table does OPTIMIZE TABLE work for?

OPTIMIZE TABLE works for InnoDB , MyISAM, and ARCHIVE tables. OPTIMIZE TABLE is also supported for dynamic columns of in-memory NDB tables. It does not work for fixed-width columns of in-memory tables, nor does it work for Disk Data tables.

What to do when MySQL is out of disk space?

Another way to perform a defragmentation operation is to use mysqldump to dump the table to a text file, drop the table, and reload it from the dump file. Ultimately, we can also use DROP TABLE to remove the unused table or TRUNCATE TABLE to clear up all rows in the table, which consequently return the space back to the OS.

How are deleted rows maintained in MySQL 5.7?

After deleting a large part of a MyISAM or ARCHIVE table, or making many changes to a MyISAM or ARCHIVE table with variable-length rows (tables that have VARCHAR , VARBINARY , BLOB, or TEXT columns). Deleted rows are maintained in a linked list and subsequent INSERT operations reuse old row positions.