How does the myisampack utility in MySQL work?
The myisampack utility compresses MyISAM tables. myisampack works by compressing each column in the table separately. Usually, myisampack packs the data file 40% to 70%. When the table is used later, the server reads into memory the information needed to decompress columns.
Which is better myisampack or table decompression?
Usually, myisampack packs the data file 40% to 70%. When the table is used later, the server reads into memory the information needed to decompress columns. This results in much better performance when accessing individual rows, because you only have to uncompress exactly one row.
Why does MySQL use mmap on compressed tables?
When the table is used later, the server reads into memory the information needed to decompress columns. This results in much better performance when accessing individual rows, because you only have to uncompress exactly one row. MySQL uses mmap () when possible to perform memory mapping on compressed tables.
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 are the features of the MyISAM storage engine?
MyISAM also supports the following features: Support for a true VARCHAR type; a VARCHAR column starts with a length stored in one or two bytes. Tables with VARCHAR columns may have fixed or dynamic row length. The sum of the lengths of the VARCHAR and CHAR columns in a table may be up to 64KB.
Where is the MyISAM table definition stored in MySQL?
The table definition is stored in the MySQL data dictionary. To specify explicitly that you want a MyISAM table, indicate that with an ENGINE table option: In MySQL 8.0, it is normally necessary to use ENGINE to specify the MyISAM storage engine because InnoDB is the default engine.