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MongoDB\Collection::explain()

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  • Definition
  • Parameters
  • Return Values
  • Errors/Exceptions
  • Explainable Commands
  • Examples
  • See Also

New in version 1.4.

MongoDB\\Collection::explain()

Explain the given command.

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

An array specifying the desired options.

Name
Type
Description
comment
mixed

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

This option is available since MongoDB 4.4 and will result in an exception at execution time if specified for an older server version.

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

New in version 1.13.

readPreference

Read preference to use for the operation. Defaults to the collection's read preference.

typeMap
array

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

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

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 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

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)
}
}
  • explain command reference in the MongoDB manual

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