CACHE INDEXtbl_index_list
[,tbl_index_list
] ... INkey_cache_name
tbl_index_list
:tbl_name
[[INDEX|KEY] (index_name
[,index_name
] ...)]
The CACHE INDEX
statement assigns
table indexes to a specific key cache. It is used only for
MyISAM
tables.
The following statement assigns indexes from the tables
t1
, t2
, and
t3
to the key cache named
hot_cache
:
mysql> CACHE INDEX t1, t2, t3 IN hot_cache;
+---------+--------------------+----------+----------+
| Table | Op | Msg_type | Msg_text |
+---------+--------------------+----------+----------+
| test.t1 | assign_to_keycache | status | OK |
| test.t2 | assign_to_keycache | status | OK |
| test.t3 | assign_to_keycache | status | OK |
+---------+--------------------+----------+----------+
The syntax of CACHE INDEX
enables
you to specify that only particular indexes from a table should
be assigned to the cache. The current implementation assigns all
the table's indexes to the cache, so there is no reason to
specify anything other than the table name.
The key cache referred to in a CACHE
INDEX
statement can be created by setting its size
with a parameter setting statement or in the server parameter
settings. For example:
mysql> SET GLOBAL keycache1.key_buffer_size=128*1024;
Key cache parameters can be accessed as members of a structured system variable. See Section 5.1.6.1, “Structured System Variables”.
A key cache must exist before you can assign indexes to it:
mysql> CACHE INDEX t1 IN non_existent_cache;
ERROR 1284 (HY000): Unknown key cache 'non_existent_cache'
By default, table indexes are assigned to the main (default) key cache created at the server startup. When a key cache is destroyed, all indexes assigned to it become assigned to the default key cache again.
Index assignment affects the server globally: If one client assigns an index to a given cache, this cache is used for all queries involving the index, no matter which client issues the queries.
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