Php/docs/function.mysqlnd-qc-set-is-select
mysqlnd_qc_set_is_select
(PECL mysqlnd_qc >= 1.0.0)
mysqlnd_qc_set_is_select — Installs a callback which decides whether a statement is cached
说明
mysqlnd_qc_set_is_select
(
string
$callback
) : mixed
Installs a callback which decides whether a statement is cached.
There are several ways of hinting PELC/mysqlnd_qc to cache a query.
By default, PECL/mysqlnd_qc attempts to cache a if caching of all statements
is enabled or the query string begins with a certain SQL hint.
The plugin internally calls a function named is_select()
to find out. This internal function can be replaced with a user-defined callback.
Then, the user-defined callback is responsible to decide whether the plugin
attempts to cache a statement. Because the internal function is replaced
with the callback, the callback gains full control. The callback is free
to ignore the configuration setting mysqlnd_qc.cache_by_default
and SQL hints.
The callback is invoked for every statement inspected by the plugin.
It is given the statements string as a parameter. The callback returns
false if the statement shall not be cached. It returns true to
make the plugin attempt to cache the statements result set, if any.
A so-created cache entry is given the default TTL set with the
PHP configuration directive mysqlnd_qc.ttl.
If a different TTL shall be used, the callback returns a numeric
value to be used as the TTL.
The internal is_select function is part of the internal
cache storage handler interface. Thus, a user-defined storage handler
offers the same capabilities.
参数
此函数没有参数。
返回值
成功时返回 true， 或者在失败时返回 false。
范例
Example #1 mysqlnd_qc_set_is_select() example
<?php/* callback which decides if query is cached */function is_select($query) { static $patterns = array( /* true - use default from mysqlnd_qc.ttl */ "@SELECT\s+.*\s+FROM\s+test@ismU" => true, /* 3 - use TTL = 3 seconds */ "@SELECT\s+.*\s+FROM\s+news@ismU" => 3 ); /* check if query does match pattern */ foreach ($patterns as $pattern => $ttl) { if (preg_match($pattern, $query)) { printf("is_select(%45s): cache\n", $query); return $ttl; } } printf("is_select(%45s): do not cache\n", $query); return false;}mysqlnd_qc_set_is_select("is_select");/* Connect, create and populate test table */$mysqli = new mysqli("host", "user", "password", "schema");$mysqli->query("DROP TABLE IF EXISTS test");$mysqli->query("CREATE TABLE test(id INT)");$mysqli->query("INSERT INTO test(id) VALUES (1), (2), (3)");/* cache put */$mysqli->query("SELECT id FROM test WHERE id = 1");/* cache hit */$mysqli->query("SELECT id FROM test WHERE id = 1");/* cache put */$mysqli->query("SELECT * FROM test");?>
以上例程会输出：
is_select( DROP TABLE IF EXISTS test): do not cache is_select( CREATE TABLE test(id INT)): do not cache is_select( INSERT INTO test(id) VALUES (1), (2), (3)): do not cache is_select( SELECT id FROM test WHERE id = 1): cache is_select( SELECT id FROM test WHERE id = 1): cache is_select( SELECT * FROM test): cache
参见
- Runtime configuration
- mysqlnd_qc.ttl
- mysqlnd_qc.cache_by_default
- mysqlnd_qc_set_user_handlers() - Sets the callback functions for a user-defined procedural storage handler
