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The query cache plugin supports the use of user-defined storage handler. User-defined storage handler can use arbitrarily complex invalidation algorithms and support arbitrary storage media.
All user-defined storage handlers have to provide a certain interface. The functions of the user-defined storage handler will be called by the core of the cache plugin. The necessary interface consists of seven public functions. Both procedural and object oriented user-defined storage handler must implement the same set of functions.
Example #1 Using a user-defined storage handler
<?php
ini_set ( "mysqlnd_qc.cache_by_default" , 1 );
$__cache = array();
function get_hash ( $host_info , $port , $user , $db , $query ) {
global $__cache ;
printf ( "\t%s(%d)\n" , __FUNCTION__ , func_num_args ());
return md5 ( sprintf ( "%s%s%s%s%s" , $host_info , $port , $user , $db , $query ));
}
function find_query_in_cache ( $key ) {
global $__cache ;
printf ( "\t%s(%d)\n" , __FUNCTION__ , func_num_args ());
if (isset( $__cache [ $key ])) {
$tmp = $__cache [ $key ];
if ( $tmp [ "valid_until" ] < time ()) {
unset( $__cache [ $key ]);
$ret = NULL ;
} else {
$ret = $__cache [ $key ][ "data" ];
}
} else {
$ret = NULL ;
}
return $ret ;
}
function return_to_cache ( $key ) {
printf ( "\t%s(%d)\n" , __FUNCTION__ , func_num_args ());
}
function add_query_to_cache_if_not_exists ( $key , $data , $ttl , $run_time , $store_time , $row_count ) {
global $__cache ;
printf ( "\t%s(%d)\n" , __FUNCTION__ , func_num_args ());
$__cache [ $key ] = array(
"data" => $data ,
"row_count" => $row_count ,
"valid_until" => time () + $ttl ,
"hits" => 0 ,
"run_time" => $run_time ,
"store_time" => $store_time ,
"cached_run_times" => array(),
"cached_store_times" => array(),
);
return TRUE ;
}
function query_is_select ( $query ) {
printf ( "\t%s('%s'): " , __FUNCTION__ , $query );
$ret = FALSE ;
if ( stristr ( $query , "SELECT" ) !== FALSE ) {
$ret = 5 ;
}
printf ( "%s\n" , ( FALSE === $ret ) ? "FALSE" : $ret );
return $ret ;
}
function update_query_run_time_stats ( $key , $run_time , $store_time ) {
global $__cache ;
printf ( "\t%s(%d)\n" , __FUNCTION__ , func_num_args ());
if (isset( $__cache [ $key ])) {
$__cache [ $key ][ 'hits' ]++;
$__cache [ $key ][ "cached_run_times" ][] = $run_time ;
$__cache [ $key ][ "cached_store_times" ][] = $store_time ;
}
}
function get_stats ( $key = NULL ) {
global $__cache ;
printf ( "\t%s(%d)\n" , __FUNCTION__ , func_num_args ());
if ( $key && isset( $__cache [ $key ])) {
$stats = $__cache [ $key ];
} else {
$stats = array();
foreach ( $__cache as $key => $details ) {
$stats [ $key ] = array(
'hits' => $details [ 'hits' ],
'bytes' => strlen ( $details [ 'data' ]),
'uncached_run_time' => $details [ 'run_time' ],
'cached_run_time' => ( count ( $details [ 'cached_run_times' ]))
? array_sum ( $details [ 'cached_run_times' ]) / count ( $details [ 'cached_run_times' ])
: 0 ,
);
}
}
return $stats ;
}
function clear_cache () {
global $__cache ;
printf ( "\t%s(%d)\n" , __FUNCTION__ , func_num_args ());
$__cache = array();
return TRUE ;
}
if (! mysqlnd_qc_set_user_handlers ( "get_hash" , "find_query_in_cache" ,
"return_to_cache" , "add_query_to_cache_if_not_exists" ,
"query_is_select" , "update_query_run_time_stats" , "get_stats" , "clear_cache" )) {
printf ( "Failed to install user-defined storage handler\n" );
}
$mysqli = new mysqli ( "host" , "user" , "password" , "schema" , "port" , "socket" );
$mysqli -> query ( "DROP TABLE IF EXISTS test" );
$mysqli -> query ( "CREATE TABLE test(id INT)" );
$mysqli -> query ( "INSERT INTO test(id) VALUES (1), (2)" );
printf ( "\nCache put/cache miss\n" );
$res = $mysqli -> query ( "SELECT id FROM test WHERE id = 1" );
var_dump ( $res -> fetch_assoc ());
$res -> free ();
$mysqli -> query ( "DELETE FROM test WHERE id = 1" );
printf ( "\nCache hit\n" );
$res = $mysqli -> query ( "SELECT id FROM test WHERE id = 1" );
var_dump ( $res -> fetch_assoc ());
$res -> free ();
printf ( "\nDisplay cache statistics\n" );
var_dump ( mysqlnd_qc_get_cache_info ());
printf ( "\nFlushing cache, cache put/cache miss" );
var_dump ( mysqlnd_qc_clear_cache ());
$res = $mysqli -> query ( "SELECT id FROM test WHERE id = 1" );
var_dump ( $res -> fetch_assoc ());
$res -> free ();
?>
以上例程的输出类似于:
query_is_select('DROP TABLE IF EXISTS test'): FALSE query_is_select('CREATE TABLE test(id INT)'): FALSE query_is_select('INSERT INTO test(id) VALUES (1), (2)'): FALSECache put/cache miss query_is_select('SELECT id FROM test WHERE id = 1'): 5 get_hash(5) find_query_in_cache(1) add_query_to_cache_if_not_exists(6) array(1) { ["id"]=> string(1) "1" } query_is_select('DELETE FROM test WHERE id = 1'): FALSECache hit query_is_select('SELECT id FROM test WHERE id = 1'): 5 get_hash(5) find_query_in_cache(1) return_to_cache(1) update_query_run_time_stats(3) array(1) { ["id"]=> string(1) "1" }Display cache statistics get_stats(0) array(4) { ["num_entries"]=> int(1) ["handler"]=> string(4) "user" ["handler_version"]=> string(5) "1.0.0" ["data"]=> array(1) { ["18683c177dc89bb352b29965d112fdaa"]=> array(4) { ["hits"]=> int(1) ["bytes"]=> int(71) ["uncached_run_time"]=> int(398) ["cached_run_time"]=> int(4) } } }Flushing cache, cache put/cache miss clear_cache(0) bool(true) query_is_select('SELECT id FROM test WHERE id = 1'): 5 get_hash(5) find_query_in_cache(1) add_query_to_cache_if_not_exists(6) NULL