MYSQLND_QC_SET_IS_SELECT(3)						 1					       MYSQLND_QC_SET_IS_SELECT(3)

mysqlnd_qc_set_is_select - Installs a callback which decides whether a statement is cached

SYNOPSIS

       mixed mysqlnd_qc_set_is_select (string  $callback)

DESCRIPTION

	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(3) example

	      <?php
	      /* callback which decides if query is cached */
	      function is_select($query) {
		static $patterns = array(
		 /* true - use default from mysqlnd_qc.ttl */
		 "@SELECTs+.*s+FROMs+test@ismU" => true,
		 /* 3 - use TTL = 3 seconds */
		 "@SELECTs+.*s+FROMs+news@ismU" => 3
		);
		/* check if query does match pattern */
		foreach ($patterns as $pattern => $ttl) {
		  if (preg_match($pattern, $query)) {
		    printf("is_select(%45s): cache
", $query);
		    return $ttl;
		  }
		}
		printf("is_select(%45s): do not cache
", $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(3).

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