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MongoDB\Collection::explain()

New in version 1.4.

Definition

MongoDB\Collection::explain

Explain the given command.

function explain(MongoDB\\Operation\\Explainable $explainable, array $options = []): array|object

This method has the following parameters:

Parameter Type Description
$explainable MongoDB\Operation\Explainable The command to explain.
$options array Optional. An array specifying the desired options.

The $options parameter supports the following options:

Option Type Description
comment mixed

Optional. Enables users to specify an arbitrary comment to help trace the operation through the database profiler, currentOp output, and logs.

Defaults to the comment of the explained operation (if any).

This is not supported for server versions prior to 4.4 and will result in an exception at execution time if used.

New in version 1.13.

readPreference MongoDB\Driver\ReadPreference Optional. Read preference to use for the operation. Defaults to the collection’s read preference.
typeMap array

Optional. The type map to apply to cursors, which determines how BSON documents are converted to PHP values. Defaults to the collection’s type map.

This will be used for the returned command result document.

verbosity string Optional. The verbosity level at which to run the command. See the explain command for more information.

Return Values

An array or object with the result document of the explain command. The return type will depend on the typeMap option.

Errors/Exceptions

MongoDB\Exception\UnsupportedException if options are used and not supported by the selected server (e.g. collation, readConcern, writeConcern).

MongoDB\Exception\InvalidArgumentException for errors related to the parsing of parameters or options.

MongoDB\Driver\Exception\RuntimeException for other errors at the driver level (e.g. connection errors).

Explainable Commands

Explainable commands include, but are not limited to:

  • MongoDB\Operation\Aggregate
  • MongoDB\Operation\Count
  • MongoDB\Operation\DeleteMany
  • MongoDB\Operation\DeleteOne
  • MongoDB\Operation\Distinct
  • MongoDB\Operation\Find
  • MongoDB\Operation\FindOne
  • MongoDB\Operation\FindOneAndDelete
  • MongoDB\Operation\FindOneAndReplace
  • MongoDB\Operation\FindOneAndUpdate
  • MongoDB\Operation\UpdateMany
  • MongoDB\Operation\UpdateOne

Examples

This example explains a count command.

<?php

$collection = (new MongoDB\Client)->test->restaurants;

$count = new MongoDB\Operation\Count(
    $collection->getDatabaseName(),
    $collection->getCollectionName(),
    ['cuisine' => 'Italian']
);

$result = $collection->explain($count);

var_dump($result);

The output would then resemble:

object(MongoDB\Model\BSONDocument)#29 (1) {
  ["storage":"ArrayObject":private]=>
  array(4) {
    ["queryPlanner"]=>
    object(MongoDB\Model\BSONDocument)#21 (1) {
      ["storage":"ArrayObject":private]=>
      array(6) {
        ["plannerVersion"]=>
        int(1)
        ["namespace"]=>
        string(16) "test.restaurants"
        ["indexFilterSet"]=>
        bool(false)
        ["parsedQuery"]=>
        object(MongoDB\Model\BSONDocument)#15 (1) {
          ["storage":"ArrayObject":private]=>
          array(1) {
            ["cuisine"]=>
            object(MongoDB\Model\BSONDocument)#14 (1) {
              ["storage":"ArrayObject":private]=>
              array(1) {
                ["$eq"]=>
                string(7) "Italian"
              }
            }
          }
        }
        ["winningPlan"]=>
        object(MongoDB\Model\BSONDocument)#19 (1) {
          ["storage":"ArrayObject":private]=>
          array(2) {
            ["stage"]=>
            string(5) "COUNT"
            ["inputStage"]=>
            object(MongoDB\Model\BSONDocument)#18 (1) {
              ["storage":"ArrayObject":private]=>
              array(3) {
                ["stage"]=>
                string(8) "COLLSCAN"
                ["filter"]=>
                object(MongoDB\Model\BSONDocument)#17 (1) {
                  ["storage":"ArrayObject":private]=>
                  array(1) {
                    ["cuisine"]=>
                    object(MongoDB\Model\BSONDocument)#16 (1) {
                      ["storage":"ArrayObject":private]=>
                      array(1) {
                        ["$eq"]=>
                        string(7) "Italian"
                      }
                    }
                  }
                }
                ["direction"]=>
                string(7) "forward"
              }
            }
          }
        }
        ["rejectedPlans"]=>
        object(MongoDB\Model\BSONArray)#20 (1) {
          ["storage":"ArrayObject":private]=>
          array(0) {
          }
        }
      }
    }
    ["executionStats"]=>
    object(MongoDB\Model\BSONDocument)#27 (1) {
      ["storage":"ArrayObject":private]=>
      array(7) {
        ["executionSuccess"]=>
        bool(true)
        ["nReturned"]=>
        int(0)
        ["executionTimeMillis"]=>
        int(24)
        ["totalKeysExamined"]=>
        int(0)
        ["totalDocsExamined"]=>
        int(25359)
        ["executionStages"]=>
        object(MongoDB\Model\BSONDocument)#25 (1) {
          ["storage":"ArrayObject":private]=>
          array(14) {
            ["stage"]=>
            string(5) "COUNT"
            ["nReturned"]=>
            int(0)
            ["executionTimeMillisEstimate"]=>
            int(20)
            ["works"]=>
            int(25361)
            ["advanced"]=>
            int(0)
            ["needTime"]=>
            int(25360)
            ["needYield"]=>
            int(0)
            ["saveState"]=>
            int(198)
            ["restoreState"]=>
            int(198)
            ["isEOF"]=>
            int(1)
            ["invalidates"]=>
            int(0)
            ["nCounted"]=>
            int(1069)
            ["nSkipped"]=>
            int(0)
            ["inputStage"]=>
            object(MongoDB\Model\BSONDocument)#24 (1) {
              ["storage":"ArrayObject":private]=>
              array(14) {
                ["stage"]=>
                string(8) "COLLSCAN"
                ["filter"]=>
                object(MongoDB\Model\BSONDocument)#23 (1) {
                  ["storage":"ArrayObject":private]=>
                  array(1) {
                    ["cuisine"]=>
                    object(MongoDB\Model\BSONDocument)#22 (1) {
                      ["storage":"ArrayObject":private]=>
                      array(1) {
                        ["$eq"]=>
                        string(7) "Italian"
                      }
                    }
                  }
                }
                ["nReturned"]=>
                int(1069)
                ["executionTimeMillisEstimate"]=>
                int(20)
                ["works"]=>
                int(25361)
                ["advanced"]=>
                int(1069)
                ["needTime"]=>
                int(24291)
                ["needYield"]=>
                int(0)
                ["saveState"]=>
                int(198)
                ["restoreState"]=>
                int(198)
                ["isEOF"]=>
                int(1)
                ["invalidates"]=>
                int(0)
                ["direction"]=>
                string(7) "forward"
                ["docsExamined"]=>
                int(25359)
              }
            }
          }
        }
        ["allPlansExecution"]=>
        object(MongoDB\Model\BSONArray)#26 (1) {
          ["storage":"ArrayObject":private]=>
          array(0) {
          }
        }
      }
    }
    ["serverInfo"]=>
    object(MongoDB\Model\BSONDocument)#28 (1) {
      ["storage":"ArrayObject":private]=>
      array(4) {
        ["host"]=>
        string(9) "localhost"
        ["port"]=>
        int(27017)
        ["version"]=>
        string(5) "3.6.1"
        ["gitVersion"]=>
        string(40) "025d4f4fe61efd1fb6f0005be20cb45a004093d1"
      }
    }
    ["ok"]=>
    float(1)
  }
}

See Also

  • explain command reference in the MongoDB manual