Provided by: libmongodb-perl_1.8.1-1_amd64 
NAME
MongoDB::GridFSBucket - A file storage abstraction
VERSION
version v1.8.1
SYNOPSIS
$bucket = $database->gfs;
# upload a file
$stream = $bucket->open_upload_stream("foo.txt");
$stream->print( $data );
$stream->close;
# find and download a file
$result = $bucket-find({filename => "foo.txt"});
$file_id = $result->next->{_id};
$stream = $bucket->open_download_stream($file_id)
$data = do { local $/; $stream->readline() };
DESCRIPTION
This class models a GridFS file store in a MongoDB database and provides an API for
interacting with it.
Generally, you never construct one of these directly with "new". Instead, you call "gfs"
(short for "get_gridfsbucket") on a MongoDB::Database object.
USAGE
Data model
A GridFS file is represented in MongoDB as a "file document" with information like the
file's name, length, MD5 hash, and any user-supplied metadata. The actual contents are
stored as a number of "chunks" of binary data. (Think of the file document as a directory
entry and the chunks like blocks on disk.)
Valid file documents typically include the following fields:
• _id – a unique ID for this document, typically type BSON ObjectId.
• length – the length of this stored file, in bytes
• chunkSize – the size, in bytes, of each full data chunk of this file. This value is
configurable per file.
• uploadDate – the date and time this file was added to GridFS, stored as a BSON
datetime value.
• md5 – a hash of the contents of the stored file
• filename – the name of this stored file; the combination of filename and uploadDate
(millisecond resolution) must be unique
• metadata – any additional application data the user wishes to store (optional)
• contentType – DEPRECATED (store this in "metadata" if you need it) (optional)
• aliases – DEPRECATED (store this in "metadata" if you need it) (optional)
The "find" method searches file documents using these fields. Given the "_id" from a
document, a file can be downloaded using the download methods.
API Overview
In addition to general methods like "find", "delete" and "drop", there are two ways to go
about uploading and downloading:
• filehandle-like: you get an object that you can read/write from similar to a
filehandle. You can even get a tied filehandle that you can hand off to other code
that requires an actual Perl handle.
• streaming: you provide a file handle to read from (upload) or print to (download) and
data is streamed to (upload) or from (download) GridFS until EOF.
Error handling
Unless otherwise explicitly documented, all methods throw exceptions if an error occurs.
The error types are documented in MongoDB::Error.
ATTRIBUTES
database
The MongoDB::Database containing the GridFS bucket collections.
bucket_name
The name of the GridFS bucket. Defaults to 'fs'. The underlying collections that are
used to implement a GridFS bucket get this string as a prefix (e.g "fs.chunks").
chunk_size_bytes
The number of bytes per chunk. Defaults to 261120 (255kb).
write_concern
A MongoDB::WriteConcern object. It may be initialized with a hash reference that will be
coerced into a new MongoDB::WriteConcern object. By default it will be inherited from a
MongoDB::Database object.
read_concern
A MongoDB::ReadConcern object. May be initialized with a hash reference or a string that
will be coerced into the level of read concern.
By default it will be inherited from a MongoDB::Database object.
read_preference
A MongoDB::ReadPreference object. It may be initialized with a string corresponding to
one of the valid read preference modes or a hash reference that will be coerced into a new
MongoDB::ReadPreference object. By default it will be inherited from a MongoDB::Database
object.
Note: Because many GridFS operations require multiple independent reads from separate
collections, use with secondaries is strongly discouraged because reads could go to
different secondaries, resulting in inconsistent data if all file and chunk documents have
not replicated to all secondaries.
bson_codec
An object that provides the "encode_one" and "decode_one" methods, such as from
MongoDB::BSON. It may be initialized with a hash reference that will be coerced into a
new MongoDB::BSON object. By default it will be inherited from a MongoDB::Database
object.
max_time_ms
Specifies the maximum amount of time in milliseconds that the server should use for
working on a query. By default it will be inherited from a MongoDB::Database object.
Note: this will only be used for server versions 2.6 or greater, as that was when the
$maxTimeMS meta-operator was introduced.
METHODS
find
$result = $bucket->find($filter);
$result = $bucket->find($filter, $options);
$file_doc = $result->next;
Executes a query on the file documents collection with a filter expression and returns a
MongoDB::QueryResult object. It takes an optional hashref of options identical to "find"
in MongoDB::Collection.
find_one
$file_doc = $bucket->find_one($filter, $projection);
$file_doc = $bucket->find_one($filter, $projection, $options);
Executes a query on the file documents collection with a filter expression and returns the
first document found, or "undef" if no document is found.
See "find_one" in MongoDB::Collection for details about the $projection and optional
$options fields.
find_id
$file_doc = $bucket->find_id( $id );
$file_doc = $bucket->find_id( $id, $projection );
$file_doc = $bucket->find_id( $id, $projection, $options );
Executes a query with a filter expression of "{ _id => $id }" and returns a single
document or "undef" if no document is found.
See "find_one" in MongoDB::Collection for details about the $projection and optional
$options fields.
open_download_stream
$stream = $bucket->open_download_stream($id);
$line = $stream->readline;
Returns a new MongoDB::GridFSBucket::DownloadStream that can be used to download the file
with the file document "_id" matching $id. This throws a MongoDB::GridFSError if no such
file exists.
open_upload_stream
$stream = $bucket->open_upload_stream($filename);
$stream = $bucket->open_upload_stream($filename, $options);
$stream->print('data');
$stream->close;
$file_id = $stream->id
Returns a new MongoDB::GridFSBucket::UploadStream that can be used to upload a new file to
a GridFS bucket.
This method requires a filename to store in the "filename" field of the file document.
Note: the filename is an arbitrary string; the method does not read from this filename
locally.
You can provide an optional hash reference of options that are passed to the
MongoDB::GridFSBucket::UploadStream constructor:
• "chunk_size_bytes" – the number of bytes per chunk. Defaults to the
"chunk_size_bytes" of the bucket object.
• "metadata" – a hash reference for storing arbitrary metadata about the file.
open_upload_stream_with_id
$stream = $bucket->open_upload_stream_with_id($id, $filename);
$stream = $bucket->open_upload_stream_with_id($id, $filename, $options);
$stream->print('data');
$stream->close;
Returns a new MongoDB::GridFSBucket::UploadStream that can be used to upload a new file to
a GridFS bucket.
This method uses $id as the _id of the file being created, which must be unique.
This method requires a filename to store in the "filename" field of the file document.
Note: the filename is an arbitrary string; the method does not read from this filename
locally.
You can provide an optional hash reference of options, just like "open_upload_stream".
download_to_stream
$bucket->download_to_stream($id, $out_fh);
Downloads the file matching $id and writes it to the file handle $out_fh. This throws a
MongoDB::GridFSError if no such file exists.
upload_from_stream
$file_id = $bucket->upload_from_stream($filename, $in_fh);
$file_id = $bucket->upload_from_stream($filename, $in_fh, $options);
Reads from a filehandle and uploads its contents to GridFS. It returns the "_id" field
stored in the file document.
This method requires a filename to store in the "filename" field of the file document.
Note: the filename is an arbitrary string; the method does not read from this filename
locally.
You can provide an optional hash reference of options, just like "open_upload_stream".
upload_from_stream_with_id
$bucket->upload_from_stream_with_id($id, $filename, $in_fh);
$bucket->upload_from_stream_with_id($id, $filename, $in_fh, $options);
Reads from a filehandle and uploads its contents to GridFS.
This method uses $id as the _id of the file being created, which must be unique.
This method requires a filename to store in the "filename" field of the file document.
Note: the filename is an arbitrary string; the method does not read from this filename
locally.
You can provide an optional hash reference of options, just like "open_upload_stream".
Unlike "open_upload_stream", this method returns nothing.
delete
$bucket->delete($id);
Deletes the file matching $id from the bucket. This throws a MongoDB::GridFSError if no
such file exists.
drop
$bucket->drop;
Drops the underlying files documents and chunks collections for this bucket.
SEE ALSO
Core documentation on GridFS: <http://dochub.mongodb.org/core/gridfs>.
AUTHORS
• David Golden <david@mongodb.com>
• Rassi <rassi@mongodb.com>
• Mike Friedman <friedo@friedo.com>
• Kristina Chodorow <k.chodorow@gmail.com>
• Florian Ragwitz <rafl@debian.org>
COPYRIGHT AND LICENSE
This software is Copyright (c) 2018 by MongoDB, Inc.
This is free software, licensed under:
The Apache License, Version 2.0, January 2004