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Collection Statistics Reference¶
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Synopsis¶
To fetch collection statistics, call the db.collection.stats()
method on
a collection object in the mongo
shell:
You may also use the literal command format:
Replace collection
in both examples with the name of the
collection you want statistics for. By default, the return values will
appear in terms of bytes. You can, however, enter a scale
argument. For example, you can convert the return values to kilobytes
like so:
Or:
Note
The scale
argument rounds values to whole numbers. This can
produce unpredictable and unexpected results in some situations.
See also
The documentation of the “collStats
” command
and the “db.collection.stats()
,” method in the mongo
shell.
Example Document¶
The output of db.collection.stats()
resembles the following:
Fields¶
-
collStats.
ns
¶ The namespace of the current collection, which follows the format
[database].[collection]
.
-
collStats.
count
¶ The number of objects or documents in this collection.
-
collStats.
size
¶ The size of the data stored in this collection. This value does not include the size of any indexes associated with the collection, which the
totalIndexSize
field reports.The
scale
argument affects this value.
-
collStats.
avgObjSize
¶ The average size of an object in the collection. The
scale
argument affects this value.
-
collStats.
storageSize
¶ The total amount of storage allocated to this collection for document storage. The
scale
argument affects this value. ThestorageSize
does not decrease as you remove or shrink documents.
-
collStats.
numExtents
¶ The total number of contiguously allocated data file regions.
-
collStats.
nindexes
¶ The number of indexes on the collection. All collections have at least one index on the _id field.
Changed in version 2.2: Before 2.2, capped collections did not necessarily have an index on the
_id
field, and some capped collections created with pre-2.2 versions ofmongod
may not have an_id
index.
-
collStats.
lastExtentSize
¶ The size of the last extent allocated. The
scale
argument affects this value.
-
collStats.
paddingFactor
¶ The amount of space added to the end of each document at insert time. The document padding provides a small amount of extra space on disk to allow a document to grow slightly without needing to move the document.
mongod
automatically calculates this padding factor
-
collStats.
flags
¶ Changed in version 2.2: Removed in version 2.2 and replaced with the
userFlags
andsystemFlags
fields.Indicates the number of flags on the current collection. In version 2.0, the only flag notes the existence of an index on the _id field.
-
collStats.
systemFlags
¶ New in version 2.2.
Reports the flags on this collection that reflect internal server options. Typically this value is
1
and reflects the existence of an index on the_id
field.
-
collStats.
userFlags
¶ New in version 2.2.
Reports the flags on this collection set by the user. In version 2.2 the only user flag is
usePowerOf2Sizes
. IfusePowerOf2Sizes
is enabled,userFlags
will be set to1
, otherwiseuserFlags
will be0
.See the
collMod
command for more information on setting user flags andusePowerOf2Sizes
.
-
collStats.
totalIndexSize
¶ The total size of all indexes. The
scale
argument affects this value.
-
collStats.
indexSizes
¶ This field specifies the key and size of every existing index on the collection. The
scale
argument affects this value.