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Beyond TTL: user-defined storage


Beyond TTL: user-defined storage

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
/* Enable default caching of all statements */
ini_set("mysqlnd_qc.cache_by_default"1);

/* Procedural user defined storage handler functions */

$__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) {
    
/*
     Called on cache hit after cached data has been processed,
     may be used for reference counting
    */
    
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) {
        
/* cache for 5 seconds */
        
$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;
}

/* Install procedural user-defined storage handler */
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");
}


/* Connect, create and populate test table */
$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();

/* Delete record to verify we get our data from the cache */
$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();
?>

The above examples will output something similar to:

   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)'): FALSE Cache 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'): FALSE Cache 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 



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