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validate¶
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Definition¶
-
validate
¶ The
validate
command checks a collection’s data and indexes for correctness and returns the results.Tip
In the mongo Shell, this command can also be run through the
validate
helper method.Helper methods are convenient for mongo users, but they may not return the same level of information as database commands. In cases where the convenience is not needed or the additional return fields are required, use the database command.
The command has the following syntax:
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 wrapperdb.collection.validate()
:- If
Behavior¶
Performance¶
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.
Warning
Due to the performance impact of validation, consider running
validate
only on secondary replica set nodes.
You can use rs.stepDown()
to instruct the current
primary node to become a secondary to avoid impacting a live
primary node.
Restrictions¶
MongoDB drivers automatically set afterClusterTime for operations associated with causally
consistent sessions. Starting in MongoDB 4.2, the
validate
command no longer supports afterClusterTime. As such, validate
cannot be
associated with causally consistent sessions.
Examples¶
To validate a collection
myCollection
using the default settings (i.e.full: false
)To perform a full validation of collection
myCollection
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.
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.
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>.$<index_name>
-
validate.
indexDetails
¶ A document that contains the status of the index validation for each index.
Starting in MongoDB 4.2 (and 4.0.10+ and 3.6.13+),
indexDetails
identifies the specific index (or indexes) that is invalid. Earlier versions of MongoDB would mark all indexes as invalid, if any of the indexes were invalid.indexDetails
identifies the index by its name only. Earlier versions of MongoDB displayed the full namespace of the index; i.e.<db>.<collection>.$<index_name>
.
-
validate.
valid
¶ A boolean that is
true
ifvalidate
determines that all aspects of the collection are valid. Whenfalse
, see theerrors
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.
Note
For the
extraIndexEntries
array, the sum of all theindexKey
field sizes has a limit of 1MB where the sizes include both the keys and values for theindexKey
. 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.
Note
For the
missingIndexEntries
array, the sum of theidKey
field size and all itsindexKey
field sizes has a limit of 1MB where the field sizes include both the keys and values for theidKey
andindexKey
. 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+)