mongo-ruby-driver/lib/mongo/gridfs/grid_file_system.rb

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# encoding: UTF-8
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# --
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# Copyright (C) 2008-2011 10gen Inc.
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#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ++
module Mongo
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# A file store built on the GridFS specification featuring
# an API and behavior similar to that of a traditional file system.
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class GridFileSystem
include GridExt::InstanceMethods
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# Initialize a new GridFileSystem instance, consisting of a MongoDB database
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# and a filesystem prefix if not using the default.
#
# @param [Mongo::DB] db a MongoDB database.
# @param [String] fs_name A name for the file system. The default name, based on
# the specification, is 'fs'.
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def initialize(db, fs_name=Grid::DEFAULT_FS_NAME)
raise MongoArgumentError, "db must be a Mongo::DB." unless db.is_a?(Mongo::DB)
@db = db
@files = @db["#{fs_name}.files"]
@chunks = @db["#{fs_name}.chunks"]
@fs_name = fs_name
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@default_query_opts = {:sort => [['filename', 1], ['uploadDate', -1]], :limit => 1}
# Ensure indexes only if not connected to slave.
unless db.connection.slave_ok?
@files.create_index([['filename', 1], ['uploadDate', -1]])
@chunks.create_index([['files_id', Mongo::ASCENDING], ['n', Mongo::ASCENDING]], :unique => true)
end
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end
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# Open a file for reading or writing. Note that the options for this method only apply
# when opening in 'w' mode.
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#
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# Note that arbitary metadata attributes can be saved to the file by passing
# them is as options.
#
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# @param [String] filename the name of the file.
# @param [String] mode either 'r' or 'w' for reading from
# or writing to the file.
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# @param [Hash] opts see GridIO#new
#
# @option opts [Hash] :metadata ({}) any additional data to store with the file.
# @option opts [ObjectId] :_id (ObjectId) a unique id for
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# the file to be use in lieu of an automatically generated one.
# @option opts [String] :content_type ('binary/octet-stream') If no content type is specified,
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# the content type will may be inferred from the filename extension if the mime-types gem can be
# loaded. Otherwise, the content type 'binary/octet-stream' will be used.
# @option opts [Integer] (262144) :chunk_size size of file chunks in bytes.
# @option opts [Boolean] :delete_old (false) ensure that old versions of the file are deleted. This option
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# only work in 'w' mode. Certain precautions must be taken when deleting GridFS files. See the notes under
# GridFileSystem#delete.
# @option opts [Boolean] :safe (false) When safe mode is enabled, the chunks sent to the server
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# will be validated using an md5 hash. If validation fails, an exception will be raised.
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#
# @example
#
# # Store the text "Hello, world!" in the grid file system.
# @grid = GridFileSystem.new(@db)
# @grid.open('filename', 'w') do |f|
# f.write "Hello, world!"
# end
#
# # Output "Hello, world!"
# @grid = GridFileSystem.new(@db)
# @grid.open('filename', 'r') do |f|
# puts f.read
# end
#
# # Write a file on disk to the GridFileSystem
# @file = File.open('image.jpg')
# @grid = GridFileSystem.new(@db)
# @grid.open('image.jpg, 'w') do |f|
# f.write @file
# end
#
# @return [Mongo::GridIO]
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def open(filename, mode, opts={})
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opts = opts.dup
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opts.merge!(default_grid_io_opts(filename))
del = opts.delete(:delete_old) && mode == 'w'
file = GridIO.new(@files, @chunks, filename, mode, opts)
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return file unless block_given?
result = nil
begin
result = yield file
ensure
id = file.close
if del
self.delete do
@files.find({'filename' => filename, '_id' => {'$ne' => id}}, :fields => ['_id'])
end
end
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end
result
end
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# Delete the file with the given filename. Note that this will delete
# all versions of the file.
#
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# Be careful with this. Deleting a GridFS file can result in read errors if another process
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# is attempting to read a file while it's being deleted. While the odds for this
# kind of race condition are small, it's important to be aware of.
#
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# @param [String] filename
#
# @yield [] pass a block that returns an array of documents to be deleted.
#
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# @return [Boolean]
def delete(filename=nil)
if block_given?
files = yield
else
files = @files.find({'filename' => filename}, :fields => ['_id'])
end
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files.each do |file|
@files.remove({'_id' => file['_id']})
@chunks.remove({'files_id' => file['_id']})
end
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end
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alias_method :unlink, :delete
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private
def default_grid_io_opts(filename=nil)
{:fs_name => @fs_name, :query => {'filename' => filename}, :query_opts => @default_query_opts}
end
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end
end