MongoCollection::ensureIndex
(PECL mongo >=0.9.0)
MongoCollection::ensureIndex —
Creates an index on the specified field(s) if it does not already exist
Description
public bool MongoCollection::ensureIndex
( string|array $key|keys
[, array $options = array()
] )
Creates an index on the specified field(s) if it does not already exist.
Fields may be indexed with a direction (e.g. ascending or descending) or a
special type (e.g. text, geospatial, hashed).
Note:
This method will use the
» createIndexes
database command when communicating with MongoDB 2.6+. For previous database
versions, the method will perform an insert operation on the
special system.indexes collection.
Parameters
-
keys
-
An array specifying the index's fields as its keys. For each field, the
value is either the index direction or
» index type.
If specifying direction, specify 1 for ascending or
-1 for descending.
-
options
-
An array of options for the index creation. Currently available options
include:
"unique"
Specify TRUE to create a unique index. The default value is FALSE. This option applies only to ascending/descending indexes.
Note:
When MongoDB indexes a field, if a document does not have a value for the field, a NULL value is indexed. If multiple documents do not contain a field, a unique index will reject all but the first of those documents. The "sparse" option may be used to overcome this, since it will prevent documents without the field from being indexed.
"sparse"
Specify TRUE to create a sparse index, which only indexes documents containing a specified field. The default value is FALSE.
"expireAfterSeconds"
The value of this option should specify the number of seconds after which a document should be considered expired and automatically removed from the collection. This option is only compatible with single-field indexes where the field will contain MongoDate values.
Note:
This feature is available in MongoDB 2.2+. See » Expire Data from Collections by Setting TTL for more information.
"name"
A optional name that uniquely identifies the index.
Note:
By default, the driver will generate an index name based on the index's field(s) and ordering or type. For example, a compound index array("x" => 1, "y" => -1) would be named "x_1_y_-1" and a geospatial index array("loc" => "2dsphere") would be named "loc_2dsphere". For indexes with many fields, it is possible that the generated name might exceed MongoDB's » limit for index names. The "name" option may be used in that case to supply a shorter name.
"background"
Builds the index in the background so that building an index does not block other database activities. Specify TRUE to build in the background. The default value is FALSE.
WarningPrior to MongoDB 2.6.0, index builds on secondaries were executed as foreground operations, irrespective of this option. See » Building Indexes with Replica Sets for more information.
"socketTimeoutMS"
This option specifies the time limit, in milliseconds, for socket communication. If the server does not respond within the timeout period, a MongoCursorTimeoutException will be thrown and there will be no way to determine if the server actually handled the write or not. A value of -1 may be specified to block indefinitely. The default value for MongoClient is 30000 (30 seconds).
The following option may be used with MongoDB 2.6+:
The following options may be used with MongoDB versions before 2.8:
The following options may be used with MongoDB versions before 2.6:
"w"
See Write Concerns. The default value for MongoClient is 1.
"wTimeoutMS"
This option specifies the time limit, in milliseconds, for write concern acknowledgement. It is only applicable when "w" is greater than 1, as the timeout pertains to replication. If the write concern is not satisfied within the time limit, a MongoCursorException will be thrown. A value of 0 may be specified to block indefinitely. The default value for MongoClient is 10000 (ten seconds).
The following options are deprecated and should no longer be used:
"safe"
Deprecated. Please use the write concern "w" option.
"timeout"
Deprecated alias for "socketTimeoutMS".
"wtimeout"
Deprecated alias for "wTimeoutMS".
Return Values
Returns an array containing the status of the index creation. The array
contains whether the operation succeeded ("ok"), the
number of indexes before and after the operation
("numIndexesBefore" and
"numIndexesAfter"), and whether the collection that the
index belongs to has been created
("createdCollectionAutomatically"). If the index already
existed and did not need to be created, a "note" field may
be present in lieu of "numIndexesAfter".
With MongoDB 2.4 and earlier, a status document is only returned if the
write concern is at least
1. Otherwise, TRUE is returned. The fields in the status
document are different, except for the "ok" field, which
signals whether the index creation was successful. Additional fields are
described in the documentation for
MongoCollection::insert().
Errors/Exceptions
Throws MongoException if the index name is longer
than 128 bytes, or if the index specification is not an array.
Throws MongoDuplicateKeyException if the server could not
create the unique index due to conflicting documents.
Throws MongoResultException if the server could not
create the index due to an error.
Throws MongoCursorException if the "w" option is set and the write fails.
Throws MongoCursorTimeoutException if the "w" option is set to a value greater than one and the operation takes longer than MongoCursor::$timeout milliseconds to complete. This does not kill the operation on the server, it is a client-side timeout. The operation in MongoCollection::$wtimeout is milliseconds.
Examples
Example #1 MongoCollection::ensureIndex() example
<?php
$c = new MongoCollection($db, 'foo');
// create an index on 'x' ascending
$c->ensureIndex(array('x' => 1));
// create a unique index on 'y'
$c->ensureIndex(array('y' => 1), array('unique' => true));
// create a compound index on 'za' ascending and 'zb' descending
$c->ensureIndex(array('za' => 1, 'zb' => -1));
?>
Example #2 Geospatial Indexing
Mongo supports geospatial indexes, which allow you to search for documents
near a given location or within a shape. The following example creates a
geospatial index on the "loc" field:
<?php
$collection->ensureIndex(array('loc' => '2dsphere'));
?>
Example #3 Drop duplicates example
<?php
$collection->insert(array('username' => 'joeschmoe'));
$collection->insert(array('username' => 'joeschmoe'));
/* Index creation fails, since you cannot create a unique index on a field when
* duplicates exist.
*/
$collection->ensureIndex(array('username' => 1), array('unique' => 1));
/* MongoDB will one of the conflicting documents and allow the unique index to
* be created.
*/
$collection->ensureIndex(array('username' => 1), array('unique' => 1, 'dropDups' => 1));
/* We now have a unique index and subsequent inserts with the same username will
* fail.
*/
$collection->insert(array('username' => 'joeschmoe'));
?>