Php/docs/function.mysqlnd-qc-set-is-select

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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


Description

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.


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


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