collMod¶

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Definition
Options
Access Control
Examples

Definition¶

collMod¶

collMod makes it possible to add options to a collection or to modify view definitions. The command takes the following prototype form:

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db.runCommand( { collMod: <collection or view>, <option1>: <value1>, <option2>: <value2> ... } )

For the <collection or view>, specify the name of a collection or view in the current database.

Use the userFlags field in the db.collection.stats() output to check the options enabled for a collection.

Options¶

TTL Collections¶

index¶

The index option changes the expiration time of a TTL Collection.

Specify the key or index name, and new expiration time with a document of the form:

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{keyPattern: <index_spec> || name: <index_name>, expireAfterSeconds: <seconds> }

In this example, <index_spec> is an existing index in the collection. In cases of multiple indexes with the same key pattern, the user is required to specify the index by name. seconds is the number of seconds to subtract from the current time.

On success collMod returns a document with fields expireAfterSeconds_old and expireAfterSeconds_new set to their respective values.

On failure, collMod returns a document with no expireAfterSeconds field to update if there is no existing expireAfterSeconds field or cannot find index { **key**: 1.0 } for ns **namespace** if the specified keyPattern does not exist.

Record Allocation¶

noPadding¶

New in version 3.0.

noPadding is available for the MMAPv1 storage engine only.

noPadding disables record padding for the collection. Without padding, the record allocation size corresponds to the document size, and any updates that results in document growth will require a new allocation.

Warning

Only set noPadding to true for collections whose workloads have no update operations that cause documents to grow, such as for collections with workloads that are insert-only. For more information, see No Padding Allocation Strategy.

usePowerOf2Sizes¶

Deprecated since version 3.0.

usePowerOf2Sizes is available for the MMAPv1 storage engine only.

usePowerOf2Sizes has no effect on the allocation strategy. MongoDB 3.0 uses the power of 2 allocation as the default record allocation strategy for MMAPv1.

To disable the power of 2 allocation for a collection, use the collMod command with the noPadding option or the db.createCollection() method with the noPadding option. For more information, see MMAPv1 Record Allocation Behavior Changes.

Document Validation¶

validator¶

New in version 3.2.

validator allows users to specify validation rules or expressions for a collection. For more information, see Document Validation.

The validator option takes a document that specifies the validation rules or expressions. You can specify the expressions using the same operators as the query operators with the exception of : $geoNear, $near, $nearSphere, $text, and $where.

Note

Validation occurs during updates and inserts. Existing documents do not undergo validation checks until modification.
You cannot specify a validator for collections in the admin, local, and config databases.
You cannot specify a validator for system.* collections.

validationLevel¶

New in version 3.2.

The validationLevel determines how strictly MongoDB applies the validation rules to existing documents during an update.

`validationLevel`	Description
`"off"`	No validation for inserts or updates.
`"strict"`	Default Apply validation rules to all inserts and all updates.
`"moderate"`	Apply validation rules to inserts and to updates on existing valid documents. Do not apply rules to updates on existing invalid documents.

validationAction¶

New in version 3.2.

The validationAction option determines whether to error on invalid documents or just warn about the violations but allow invalid documents.

Important

Validation of documents only applies to those documents as determined by the validationLevel.

`validationAction`	Description
`"error"`	Default Documents must pass validation before the write occurs. Otherwise, the write operation fails.
`"warn"`	Documents do not have to pass validation. If the document fails validation, the write operation logs the validation failure.

To view the validation specifications for a collection, use the db.getCollectionInfos() method.

Views¶

viewOn¶

The underlying source collection or view for the view. The view definition is determined by applying the specified pipeline to this source.

Required if modifying a view on a MongoDB deployment that is running with access control.

pipeline¶

The aggregation pipeline that defines the view.

Required if modifying a view on a MongoDB deployment that is running with access control.

The view definition is public; i.e. db.getCollectionInfos() and explain operations on the view will include the pipeline that defines the view. As such, avoid referring directly to sensitive fields and values in view definitions.

Access Control¶

If the deployment enforces authentication/authorization, you must have the following privilege to run the collMod command:

Required Privileges

Modify a non-capped collection collMod in the database

Modify a view

collMod in the database and either:

no find on the view to modify, or
both find on the view to modify and find on the source collection/view.

The built-in role dbAdmin provides the required privileges.

Examples¶

Change Expiration Value for Indexes¶

To update the expiration value for a collection named sessions indexed on a lastAccess field from 30 minutes to 60 minutes, use the following operation:

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db.runCommand( { collMod: "sessions",
                 index: { keyPattern: { lastAccess: 1 },
                          expireAfterSeconds: 3600
                        }
})

Which will return the document:

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{ "expireAfterSeconds_old" : 1800, "expireAfterSeconds_new" : 3600, "ok" : 1 }

Add Document Validation to an Existing Collection¶

The following example adds a validator to a collection named contacts. The validator specifies that inserted or updated documents should meet at least one of the following conditions:

the phone field is a string
the email field matches the regular expression
the status field is either Unknown or Incomplete.

The moderate validationLevel specifies that only updates to existing valid documents will be checked against the validator, and the warn validationAction means that the write operation will log a validation failure for any document that does not pass validation.

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db.runCommand( { collMod: "contacts",
                 validator: { $or:
                    [
                       { phone: { $type: "string" } },
                       { email: { $regex: /@mongodb\.com$/ } },
                       { status: { $in: [ "Unknown", "Incomplete" ] } }
                    ]
                 },
                 validationLevel: "moderate",
                 validationAction: "warn"

} )

With the validator in place, the following insert operation fails validation:

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db.contacts.insert( { name: "Amanda", status: "Updated" } )

The write operation logs the failure and succeeds:

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2015-10-15T11:20:44.260-0400 W STORAGE  [conn3] Document would fail validation collection: example.contacts doc: { _id: ObjectId('561fc44c067a5d85b96274e4'), name: "Amanda", status: "Updated" }

For more information, see Document Validation.

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