MongoCursor::explain

(PECL mongo >=0.9.2)

MongoCursor::explain — Return an explanation of the query, often useful for optimization and debugging

说明

public array MongoCursor::explain ( void )

参数

此函数没有参数。

返回值

Returns an explanation of the query.

范例

Example #1 MongoCursor::explain() example

  <?php

$cursor  =  $collection -> find (array( "x" => 1 ), array( "y" ));
 $cursor -> sort (array( "z"  =>  1 ))-> limit ( 4 )-> skip ( 5 );

 var_dump ( $cursor -> explain ());

 ?>

以上例程的输出类似于：

array(8) {
  ["cursor"]=>
  string(15) "BtreeCursor x_1"
  ["startKey"]=>
  array(1) {
    ["x"]=>
    int(1)
  }
  ["endKey"]=>
  array(1) {
    ["x"]=>
    int(1)
  }
  ["nscanned"]=>
  float(4)
  ["n"]=>
  int(4)
  ["scanAndOrder"]=>
  int(1)
  ["millis"]=>
  int(3)
  ["allPlans"]=>
  array(2) {
    [0]=>
    array(3) {
      ["cursor"]=>
      string(15) "BtreeCursor x_1"
      ["startKey"]=>
      array(1) {
        ["x"]=>
        int(1)
      }
      ["endKey"]=>
      array(1) {
        ["x"]=>
        int(1)
      }
    }
    [1]=>
    array(3) {
      ["cursor"]=>
      string(11) "BasicCursor"
      ["startKey"]=>
      array(0) {
      }
      ["endKey"]=>
      array(0) {
      }
    }
  }
}

错误／异常

Throws MongoConnectionException if it cannot reach the database.

参见

MongoDB core docs on » explain.