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# mysqlnd_ms_query_is_select

(PECL mysqlnd_ms >= 1.0.0)

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

### Description

int mysqlnd_ms_query_is_select ( string `$query` )

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

`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() 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.\n", $query);
break;
case MYSQLND_MS_QUERY_USE_SLAVE:
printf("'%s' should be run on a slave.\n", $query);
break;
case MYSQLND_MS_QUERY_USE_LAST_USED:
printf("'%s' should be run on the server that has run the previous query\n", $query);
break;
default:
printf("No suggestion where to run the '%s', fallback to master recommended\n", $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

mysqlnd_ms_match_wild
mysqlnd_ms_set_qos
Mysqlnd_ms Functions
PHP Manual