Spec-Zone .ru
спецификации, руководства, описания, API
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Spec-Zone .ru
спецификации, руководства, описания, API
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To coalesce fragmented rows and eliminate wasted space that results from deleting or updating rows, run myisamchk in recovery mode:
shell> myisamchk -r tbl_name
You 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
13.7.2.4, "OPTIMIZE TABLE Syntax".
myisamchk has a number of other options that you can use to improve the performance of a table:
--analyze
or -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-index or -S: Sort the index blocks.
This optimizes seeks and makes table scans that use indexes faster.
--sort-records= or
index_num-R : Sort data rows
according to a given index. This makes your data much more localized and may speed up range-based index_numSELECT
and ORDER BY operations that use this index.
For a full description of all available options, see Section 4.6.3, "myisamchk — MyISAM Table-Maintenance Utility".