MongoDB\Collection::watch()

New in version 1.3.

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Definition
Return Values
Errors/Exceptions
Examples
See Also

Definition

MongoDB\Collection::watch

Executes a change stream operation on the collection. The change stream can be watched for collection-level changes.

function watch(array $pipeline = [], array $options = []): MongoDB\ChangeStream

This method has the following parameters:

Parameter	Type	Description
`$pipeline`	array\|object	Optional. The pipeline of stages to append to an initial `$changeStream` stage.
`$options`	array	Optional. An array specifying the desired options.

The $options parameter supports the following options:

Option	Type	Description
`batchSize`	integer	Optional. Specifies the maximum number of change events to return in each batch of the response from the MongoDB cluster.
`collation`	array\|object	Optional. Collation allows users to specify language-specific rules for string comparison, such as rules for lettercase and accent marks. When specifying collation, the `locale` field is mandatory; all other collation fields are optional. For descriptions of the fields, see Collation Document. This option is available in MongoDB 3.4+ and will result in an exception at execution time if specified for an older server version.
`fullDocument`	string	Optional. Allowed values are ‘default’ and ‘updateLookup’. Defaults to ‘default’. When set to ‘updateLookup’, the change notification for partial updates will include both a delta describing the changes to the document, as well as a copy of the entire document that was changed from some time after the change occurred. The following values are supported: `MongoDB\Operation\Watch::FULL_DOCUMENT_DEFAULT` (default) `MongoDB\Operation\Watch::FULL_DOCUMENT_UPDATE_LOOKUP` Note This is an option of the `$changeStream` pipeline stage.
`maxAwaitTimeMS`	integer	Optional. Positive integer denoting the time limit in milliseconds for the server to block a getMore operation if no data is available.
`readConcern`	MongoDB\Driver\ReadConcern	Optional. Read concern to use for the operation. Defaults to the collection’s read concern. This is not supported for server versions prior to 3.2 and will result in an exception at execution time if used. It is not possible to specify a read concern for individual operations as part of a transaction. Instead, set the `readConcern` option when starting the transaction with startTransaction.
`readPreference`	MongoDB\Driver\ReadPreference	Optional. Read preference to use for the operation. Defaults to the collection’s read preference. This is used for both the initial change stream aggregation and for server selection during an automatic resume.
`resumeAfter`	array\|object	Optional. Specifies the logical starting point for the new change stream. The `_id` field in documents returned by the change stream may be used here. Using this option in conjunction with `startAfter` and/or `startAtOperationTime` will result in a server error. The options are mutually exclusive. Note This is an option of the `$changeStream` pipeline stage.
`session`	MongoDB\Driver\Session	Optional. Client session to associate with the operation. Sessions are not supported for server versions prior to 3.6.
`startAfter`	array\|object	Optional. Specifies the logical starting point for the new change stream. The `_id` field in documents returned by the change stream may be used here. Unlike `resumeAfter`, this option can be used with a resume token from an “invalidate” event. Using this option in conjunction with `resumeAfter` and/or `startAtOperationTime` will result in a server error. The options are mutually exclusive. This is not supported for server versions prior to 4.2 and will result in an exception at execution time if used. Note This is an option of the `$changeStream` pipeline stage.
`startAtOperationTime`	MongoDB\BSON\TimestampInterface	Optional. If specified, the change stream will only provide changes that occurred at or after the specified timestamp. Command responses from a MongoDB 4.0+ server include an `operationTime` that can be used here. By default, the `operationTime` returned by the initial `aggregate` command will be used if available. Using this option in conjunction with `resumeAfter` and/or `startAfter` will result in a server error. The options are mutually exclusive. This is not supported for server versions prior to 4.0 and will result in an exception at execution time if used. Note This is an option of the `$changeStream` pipeline stage. New in version 1.4.
`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.

Return Values

A MongoDB\ChangeStream object, which allows for iteration of events in the change stream via the Iterator interface.

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

This example reports events while iterating a change stream.

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<?php

$uri = 'mongodb://rs1.example.com,rs2.example.com/?replicaSet=myReplicaSet';

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

$changeStream = $collection->watch();

for ($changeStream->rewind(); true; $changeStream->next()) {
    if ( ! $changeStream->valid()) {
        continue;
    }

    $event = $changeStream->current();

    if ($event['operationType'] === 'invalidate') {
        break;
    }

    $ns = sprintf('%s.%s', $event['ns']['db'], $event['ns']['coll']);
    $id = json_encode($event['documentKey']['_id']);

    switch ($event['operationType']) {
        case 'delete':
            printf("Deleted document in %s with _id: %s\n\n", $ns, $id);
            break;

        case 'insert':
            printf("Inserted new document in %s\n", $ns);
            echo json_encode($event['fullDocument']), "\n\n";
            break;

        case 'replace':
            printf("Replaced new document in %s with _id: %s\n", $ns, $id);
            echo json_encode($event['fullDocument']), "\n\n";
            break;

        case 'update':
            printf("Updated document in %s with _id: %s\n", $ns, $id);
            echo json_encode($event['updateDescription']), "\n\n";
            break;
    }
}

Assuming that a document was inserted, updated, and deleted while the above script was iterating the change stream, the output would then resemble:

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Inserted new document in test.user
{"_id":{"$oid":"5b329c4874083047cc05e60a"},"username":"bob"}

Inserted new document in test.products
{"_id":{"$oid":"5b329c4d74083047cc05e60b"},"name":"Widget","quantity":5}

Updated document in test.user with _id: {"$oid":"5b329a4f74083047cc05e603"}
{"updatedFields":{"username":"robert"},"removedFields":[]}

MongoDB\Collection::watch()

Definition

Return Values

Errors/Exceptions

Examples

See Also