MySQL 8.3 Release Notes
To coalesce fragmented rows and eliminate wasted space that results from deleting or updating rows, run myisamchk in recovery mode:
$> myisamchk -r tbl_nameYou can optimize a table in the same way by using the OPTIMIZE TABLE SQL statement. OPTIMIZE TABLE does a table repair and a key analysis, and also sorts the index tree so that key lookups are faster. There is also no possibility of unwanted interaction between a utility and the server, because the server does all the work when you use OPTIMIZE TABLE. See Section 15.7.3.4, “OPTIMIZE TABLE Statement”.
myisamchk has a number of other options that you can use to improve the performance of a table:
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--analyzeor-a: Perform key distribution analysis. This improves join performance by enabling the join optimizer to better choose the order in which to join the tables and which indexes it should use. -
--sort-indexor-S: Sort the index blocks. This optimizes seeks and makes table scans that use indexes faster. -
--sort-records=orindex_num-R: Sort data rows according to a given index. This makes your data much more localized and may speed up range-basedindex_numSELECTandORDER BYoperations that use this index.
For a full description of all available options, see Section 6.6.4, “myisamchk — MyISAM Table-Maintenance Utility”.