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validate

Definition

validate

The validate command checks a collection’s data and indexes for correctness and returns the results.

Note

The validate command does not support views and raises an error when run against a view.

The command has the following syntax:

db.runCommand( {
   validate: <string>,          // Collection name
   full: <boolean>             // Optional
} )

The command takes the following fields:

Field Type Description
validate string The name of the collection to validate.
full boolean

Optional. A flag that determines whether the command performs a slower but more thorough check or a faster but less thorough check.

  • If true, performs a more thorough check.
  • If false, omits some checks for a fater but less thorough check.

The default is false.

Starting in MongoDB 3.6, for the WiredTiger storage engine, only the full validation process will force a checkpoint and flush all in-memory data to disk before verifying the on-disk data.

In previous versions, the data validation process for the WT storage engine always forces a checkpoint.

The mongo shell also provides a wrapper db.collection.validate():

db.collection.validate();

Behavior

The validate command can be slow, particularly on larger data sets.

The validate command obtains an exclusive lock W on the collection. This will block all reads and writes on the collection until the operation finishes. When run on a secondary, the validate operation can block all other operations on that secondary until it finishes.

Restrictions

MongoDB drivers automatically set afterClusterTime for operations associated with causally consistent sessions. Starting in MongoDB 4.2, the validate command no longer support afterClusterTime. As such, validate cannot be associatd with causally consistent sessions.

Examples

  • To validate a collection myCollection using the default settings (i.e. full: false)

    db.runCommand( { validate: "myCollection" } )
    
  • To perform a full validation of collection myCollection

    db.runCommand( { validate: "myCollection", full: true } )
    

Validate Output

Note

The output may vary depending on the version and specific configuration of your MongoDB instance.

Specify { full: true } for more detailed output.

validate.ns

The full namespace name of the collection. Namespaces include the database name and the collection name in the form database.collection.

validate.nInvalidDocuments

The number of invalid documents in the collection.

validate.nrecords

The number of documents in the collection.

validate.nIndexes

The number of indexes on the collection.

validate.keysPerIndex

A document that contains the name and index entry count for each index on the collection.

"keysPerIndex" : {
   "_id_" : <num>,
   "<index2_name>" : <num>,
   ...
}

Starting in MongoDB 4.2 (and 4.0.10+ and 3.6.13+), keysPerIndex identifies the index by its name only. Earlier versions of MongoDB displayed the full namespace of the index; i.e. <db>.<collection>.$<index_name>

validate.indexDetails

A document that contains the status of the index validation for each index.

"indexDetails" : {
   "_id_" : {
      "valid" : <boolean>
   },
   "<index2_name>" : {
      "valid" : <boolean>
   },
   ...
}

Starting in MongoDB 4.2 (and 4.0.10+ and 3.6.13+),

  • indexDetails identifies the specific index (or indexes) that is invalid. Earlier versions of MongoDB would mark all indexes as invalid, if any of the indexes were invalid.
  • indexDetails identifies the index by its name only. Earlier versions of MongoDB displayed the full namespace of the index; i.e. <db>.<collection>.$<index_name>.
validate.valid

A boolean that is true if validate determines that all aspects of the collection are valid. When false, see the errors field for more information.

validate.errors

If the collection is not valid (i.e valid is false), this field will contain a message describing the validation error.

validate.extraIndexEntries

An array that contains information for each index entry that points to a document that does not exist in the collection.

"extraIndexEntries" : [
   {
      "indexName" : <string>,
      "recordId" : <NumberLong>,  // for the non-existent document
      "indexKey" : {
         "<key1>" : <value>,
         ...
      }
   }
   ...
]

Note

For the extraIndexEntries array, the sum of all the indexKey field sizes has a limit of 1MB where the sizes include both the keys and values for the indexKey. If the sum exceeds this size, the warning field displays a message.

Available starting in MongoDB 4.2 (and 4.0.10+ and 3.6.13+)

validate.missingIndexEntries

An array that contains information for each document that is missing the corresponding index entry.

"missingIndexEntries" : [
   {
      "indexName" : <string>,
      "recordId" : <NumberLong>,
      "idKey" : <_id key value>,     // The _id value of the document. Only present if an ``_id`` index exists.
      "indexKey" : {                 // The missing index entry
         "<key1>" : <value>,
         ...
      }
   }
   ...
 ]

Note

For the missingIndexEntries array, the sum of the idKey field size and all its indexKey field sizes has a limit of 1MB where the field sizes include both the keys and values for the idKey and indexKey. If the sum exceeds this size, the warning field displays a message.

Available starting in MongoDB 4.2 (and 4.0.10+ and 3.6.13+)

validate.ok

An integer with the value 1 when the command succeeds. If the command fails the ok field has a value of 0.

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