MYSQLND_MS_QUERY_IS_SELECT(3)						 1					     MYSQLND_MS_QUERY_IS_SELECT(3)

mysqlnd_ms_query_is_select - Find whether to send the query to the master, the slave or the last used MySQL server

SYNOPSIS

       int mysqlnd_ms_query_is_select (string  $query)

DESCRIPTION

	Finds whether to send the query to the master, the slave or the last used MySQL server.

	The plugins built-in read/write split mechanism will be used to analyze the query string to make a recommendation where to send the query.
       The built-in read/write split mechanism is very basic and simple. The plugin will recommend sending all queries to  the	MySQL  replication
       master  server  but  those which begin with SELECT, or begin with a SQL hint which enforces sending the query to a slave server. Due to the
       basic but fast algorithm the plugin may propose to run some read-only statements such as SHOW TABLES on the replication master.

PARAMETERS

	      o $query
		- Query string to test.

RETURN VALUES

	A return value of MYSQLND_MS_QUERY_USE_MASTER indicates that the query should be send to the MySQL replication master server. The function
       returns	a  value  of  MYSQLND_MS_QUERY_USE_SLAVE  if  the  query  can  be  run	on  a slave because it is considered read-only. A value of
       MYSQLND_MS_QUERY_USE_LAST_USED is returned to recommend running the query on the last used server. This can either be a	MySQL  replication
       master server or a MySQL replication slave server.

	If   read   write   splitting	has   been   disabled	by   setting   mysqlnd_ms.disable_rw_split,   the   function  will  always  return
       MYSQLND_MS_QUERY_USE_MASTER or MYSQLND_MS_QUERY_USE_LAST_USED.

EXAMPLES

       Example #1

	      mysqlnd_ms_query_is_select(3) example

	      <?php
	      function is_select($query)
	      {
	       switch (mysqlnd_ms_query_is_select($query))
	       {
		case MYSQLND_MS_QUERY_USE_MASTER:
		 printf("'%s' should be run on the master.
", $query);
		 break;
		case MYSQLND_MS_QUERY_USE_SLAVE:
		 printf("'%s' should be run on a slave.
", $query);
		 break;
		case MYSQLND_MS_QUERY_USE_LAST_USED:
		 printf("'%s' should be run on the server that has run the previous query
", $query);
		 break;
		default:
		 printf("No suggestion where to run the '%s', fallback to master recommended
", $query);
		 break;
	       }
	      }

	      is_select("INSERT INTO test(id) VALUES (1)");
	      is_select("SELECT 1 FROM DUAL");
	      is_select("/*" . MYSQLND_MS_LAST_USED_SWITCH . "*/SELECT 2 FROM DUAL");
	      ?>

	      The above example will output:

	      INSERT INTO test(id) VALUES (1) should be run on the master.
	      SELECT 1 FROM DUAL should be run on a slave.
	      /*ms=last_used*/SELECT 2 FROM DUAL should be run on the server that has run the previous query

SEE ALSO

       Predefined Constants, user filter .Runtime configuration, mysqlnd_ms.disable_rw_split, mysqlnd_ms.enable.

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