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GridFS Reference¶
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GridFS stores files in two collections:
chunks
stores the binary chunks. For details, see The chunks Collection.files
stores the file’s metadata. For details, see The files Collection.
GridFS places the collections in a common bucket by prefixing each
with the bucket name. By default, GridFS uses two collections with
names prefixed by fs
bucket:
fs.files
fs.chunks
You can choose a different bucket name than fs
, and create
multiple buckets in a single database.
See also
GridFS for more information about GridFS.
The chunks
Collection¶
Each document in the chunks
collection represents a distinct chunk
of a file as represented in the GridFS store. The following is a
prototype document from the chunks
collection.:
A document from the chunks
collection contains the following fields:
-
chunks.
files_id
¶ The
_id
of the “parent” document, as specified in thefiles
collection.
-
chunks.
n
¶ The sequence number of the chunk. GridFS numbers all chunks, starting with 0.
The chunks
collection uses a compound index on
files_id
and n
, as described in GridFS Index.
The files
Collection¶
Each document in the files
collection represents a file in the
GridFS store. Consider the following prototype of a document in
the files
collection:
Documents in the files
collection contain some or all of the
following fields. Applications may create additional arbitrary fields:
-
files.
_id
¶ The unique ID for this document. The
_id
is of the data type you chose for the original document. The default type for MongoDB documents is BSON ObjectId.
-
files.
length
¶ The size of the document in bytes.
-
files.
chunkSize
¶ The size of each chunk. GridFS divides the document into chunks of the size specified here. The default size is 255 kilobytes.
Changed in version 2.4.10: The default chunk size changed from 256k to 255k.
-
files.
uploadDate
¶ The date the document was first stored by GridFS. This value has the
Date
type.
-
files.
filename
¶ Optional. A human-readable name for the document.
-
files.
contentType
¶ Optional. A valid MIME type for the document.
-
files.
aliases
¶ Optional. An array of alias strings.
-
files.
metadata
¶ Optional. Any additional information you want to store.