mysqlnd_qc_set_cache_condition
mysqlnd_qc_set_storage_handler
mysqlnd_qc Functions
PHP Manual

# mysqlnd_qc_set_is_select

Installs a callback which decides whether a statement is cached

### Description

mixed mysqlnd_qc_set_is_select ( string `$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.

### Parameters

This function has no parameters.

### Return Values

Returns `TRUE` on success or `FALSE` on failure.

### Examples

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");
?>`

The above examples will output:

    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

### See Also

- Runtime configuration
- mysqlnd_qc.ttl
- mysqlnd_qc.cache_by_default
- mysqlnd_qc_set_user_handlers