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(PECL mongo >=0.9.2)
MongoCursor::explain — Return an explanation of the query, often useful for optimization and debugging
此函数没有参数。
Returns an explanation of the query.
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) { } } } }
Throws MongoConnectionException if it cannot reach the database.
MongoDB core docs on » explain.