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이 문서에서는 PHP 중국어 웹사이트 매뉴얼 풀어 주다
(PECL mysqlnd_qc >= 1.0.0)
mysqlnd_qc_set_is_select — Installs a callback which decides whether a statement is cached
$callback
)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.
此函数没有参数。
成功时返回 TRUE
, 或者在失败时返回 FALSE
。
Example #1 mysqlnd_qc_set_is_select() example
<?php
function is_select ( $query ) {
static $patterns = array(
"@SELECT\s+.*\s+FROM\s+test@ismU" => true ,
"@SELECT\s+.*\s+FROM\s+news@ismU" => 3
);
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" );
$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)" );
$mysqli -> query ( "SELECT id FROM test WHERE id = 1" );
$mysqli -> query ( "SELECT id FROM test WHERE id = 1" );
$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