MongoDB\Database::aggregate()

New in version 1.5.

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Definition
Return Values
Errors/Exceptions
Examples
See Also

Definition

MongoDB\Database::aggregate

Runs a specified admin/diagnostic pipeline which does not require an underlying collection. For aggregations on collection data, see MongoDB\Collection::aggregate().

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function aggregate(array $pipeline, array $options = []): Traversable

This method has the following parameters:

Parameter	Type	Description
`$pipeline`	array	Specifies an aggregation pipeline operation.
`$options`	array	Optional. An array specifying the desired options.

The $options parameter supports the following options:

Option	Type	Description
`allowDiskUse`	boolean	Optional. Enables writing to temporary files. When set to `true`, aggregation stages can write data to the `_tmp` sub-directory in the `dbPath` directory.
`batchSize`	integer	Optional. Specifies the initial batch size for the cursor. A batchSize of `0` means an empty first batch and is useful for quickly returning a cursor or failure message without doing significant server-side work.
`bypassDocumentValidation`	boolean	Optional. If `true`, allows the write operation to circumvent document level validation. Defaults to `false`. This only applies when using the $out and $out stages.
`comment`	string	Optional. Users can specify an arbitrary string to help trace the operation through the database profiler, currentOp, and logs.
`explain`	boolean	Optional. Specifies whether or not to return the information on the processing of the pipeline.
`hint`	string\|array\|object	Optional. The index to use. Specify either the index name as a string or the index key pattern as a document. If specified, then the query system will only consider plans using the hinted index.
`let`	array\|object	Optional. Map of parameter names and values. Values must be constant or closed expressions that do not reference document fields. Parameters can then be accessed as variables in an aggregate expression context (e.g. `$$var`). This is not supported for server versions prior to 5.0 and will result in an exception at execution time if used. New in version 1.9.
`maxTimeMS`	integer	Optional. The cumulative time limit in milliseconds for processing operations on the cursor. MongoDB aborts the operation at the earliest following interrupt point.
`readConcern`	MongoDB\Driver\ReadConcern	Optional. Read concern to use for the operation. Defaults to the database’s read concern.
`readPreference`	MongoDB\Driver\ReadPreference	Optional. Read preference to use for the operation. Defaults to the database’s read preference.
`session`	MongoDB\Driver\Session	Optional. Client session to associate with the operation.
`typeMap`	array	Optional. The type map to apply to cursors, which determines how BSON documents are converted to PHP values. Defaults to the database’s type map.
`writeConcern`	MongoDB\Driver\WriteConcern	Optional. Write concern to use for the operation. Defaults to the database’s write concern. This only applies when a $out or $merge stage is specified.

Return Values

A MongoDB\Driver\Cursor or ArrayIterator object. In both cases, the return value will be Traversable.

Errors/Exceptions

MongoDB\Exception\UnexpectedValueException if the command response from the server was malformed.

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).

Examples

The following aggregation example lists all running commands using the $currentOp aggregation pipeline stage, then filters this list to only show running command operations.