Oracle 5.0 Reference Manual page 726

•
SQL_CACHE
The query result is cached if it is cacheable and the value of the
variable is
•
SQL_NO_CACHE
The server does not use the query cache. It neither checks the query cache to see whether the
result is already cached, nor does it cache the query result. (Due to a limitation in the parser, a space
character must precede and follow the
causes the server to check the query cache to see whether the result is already cached.)
Examples:
SELECT SQL_CACHE id, name FROM customer;
SELECT SQL_NO_CACHE id, name FROM customer;
8.6.3.3. Query Cache Configuration
The
have_query_cache
mysql> SHOW VARIABLES LIKE 'have_query_cache';
+------------------+-------+
| Variable_name
+------------------+-------+
| have_query_cache | YES
+------------------+-------+
When using a standard MySQL binary, this value is always YES, even if query caching is disabled.
Several other system variables control query cache operation. These can be set in an option file or
on the command line when starting mysqld. The query cache system variables all have names that
begin with query_cache_. They are described briefly in
with additional configuration information given here.
To set the size of the query cache, set the
disables the query cache. The default size is 0, so the query cache is disabled by default.
Be careful not to set the size of the cache too large. Due to the need for threads to lock the cache
during updates, you may see lock contention issues with a very large cache.
When you set
needs a minimum size of about 40KB to allocate its structures. (The exact size depends on system
architecture.) If you set the value too small, you'll get a warning, as in this example:
mysql> SET GLOBAL query_cache_size = 40000;
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> SHOW WARNINGS\G
*************************** 1. row ***************************
Level: Warning
Code: 1282
Message: Query cache failed to set size 39936;
The MySQL Query Cache
or DEMAND.
ON
[455] server system variable indicates whether the query cache is available:
| Value |
|
Note
When using the Windows Configuration Wizard to install or configure MySQL,
the default value for
for you based on the different configuration types available. When using the
Windows Configuration Wizard, the query cache may be enabled (that is, set
to a nonzero value) due to the selected configuration. The query cache is also
controlled by the setting of the
check the values of these variables as set in your
has taken place.
query_cache_size
keyword; a nonspace such as a newline
SQL_NO_CACHE
Section 5.1.4, "Server System
query_cache_size
query_cache_size
query_cache_type
[485] to a nonzero value, keep in mind that the query cache
706
query_cache_type
[485] system variable. Setting it to 0
[485] will be configured automatically
[485] variable. You should
file after configuration
my.ini
[485] system
Variables",