650 lines
19 KiB
Ruby
650 lines
19 KiB
Ruby
# encoding: UTF-8
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# Copyright (C) 2008-2011 10gen Inc.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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module Mongo
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# A cursor over query results. Returned objects are hashes.
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class Cursor
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include Enumerable
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include Mongo::Constants
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include Mongo::Conversions
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include Mongo::Logging
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attr_reader :collection, :selector, :fields,
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:order, :hint, :snapshot, :timeout,
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:full_collection_name, :transformer,
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:options, :cursor_id, :show_disk_loc
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# Create a new cursor.
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#
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# Note: cursors are created when executing queries using [Collection#find] and other
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# similar methods. Application developers shouldn't have to create cursors manually.
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#
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# @return [Cursor]
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#
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# @core cursors constructor_details
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def initialize(collection, opts={})
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@cursor_id = nil
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@db = collection.db
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@collection = collection
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@connection = @db.connection
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@logger = @connection.logger
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@log_duration = @connection.log_duration
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# Query selector
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@selector = opts[:selector] || {}
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# Special operators that form part of $query
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@order = opts[:order]
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@explain = opts[:explain]
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@hint = opts[:hint]
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@snapshot = opts[:snapshot]
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@max_scan = opts.fetch(:max_scan, nil)
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@return_key = opts.fetch(:return_key, nil)
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@show_disk_loc = opts.fetch(:show_disk_loc, nil)
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# Wire-protocol settings
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@fields = convert_fields_for_query(opts[:fields])
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@skip = opts[:skip] || 0
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@limit = opts[:limit] || 0
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@tailable = opts[:tailable] || false
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@timeout = opts.fetch(:timeout, true)
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@options = 0
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# Use this socket for the query
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@socket = opts[:socket]
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@closed = false
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@query_run = false
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@transformer = opts[:transformer]
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if value = opts[:read]
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Mongo::Support.validate_read_preference(value)
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else
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value = collection.read_preference
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end
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@read_preference = value.is_a?(Hash) ? value.dup : value
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batch_size(opts[:batch_size] || 0)
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@full_collection_name = "#{@collection.db.name}.#{@collection.name}"
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@cache = []
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@returned = 0
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if(!@timeout)
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add_option(OP_QUERY_NO_CURSOR_TIMEOUT)
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end
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if(@read_preference != :primary)
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add_option(OP_QUERY_SLAVE_OK)
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end
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if(@tailable)
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add_option(OP_QUERY_TAILABLE)
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end
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if @collection.name =~ /^\$cmd/ || @collection.name =~ /^system/
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@command = true
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else
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@command = false
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end
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@checkin_read_pool = false
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@checkin_connection = false
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@read_pool = nil
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end
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# Guess whether the cursor is alive on the server.
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#
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# Note that this method only checks whether we have
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# a cursor id. The cursor may still have timed out
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# on the server. This will be indicated in the next
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# call to Cursor#next.
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#
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# @return [Boolean]
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def alive?
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@cursor_id && @cursor_id != 0
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end
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# Get the next document specified the cursor options.
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#
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# @return [Hash, Nil] the next document or Nil if no documents remain.
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def next
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if @cache.length == 0
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if @query_run && (@options & OP_QUERY_EXHAUST != 0)
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close
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return nil
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else
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refresh
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end
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end
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doc = @cache.shift
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if doc && doc['$err']
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err = doc['$err']
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# If the server has stopped being the master (e.g., it's one of a
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# pair but it has died or something like that) then we close that
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# connection. The next request will re-open on master server.
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if err.include?("not master")
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@connection.close
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raise ConnectionFailure.new(err, doc['code'], doc)
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end
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raise OperationFailure.new(err, doc['code'], doc)
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end
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if @transformer.nil?
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doc
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else
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@transformer.call(doc) if doc
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end
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end
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alias :next_document :next
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# Reset this cursor on the server. Cursor options, such as the
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# query string and the values for skip and limit, are preserved.
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def rewind!
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close
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@cache.clear
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@cursor_id = nil
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@closed = false
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@query_run = false
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@n_received = nil
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true
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end
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# Determine whether this cursor has any remaining results.
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#
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# @return [Boolean]
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def has_next?
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num_remaining > 0
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end
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# Get the size of the result set for this query.
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#
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# @param [Boolean] whether of not to take notice of skip and limit
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#
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# @return [Integer] the number of objects in the result set for this query.
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#
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# @raise [OperationFailure] on a database error.
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def count(skip_and_limit = false)
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command = BSON::OrderedHash["count", @collection.name, "query", @selector]
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if skip_and_limit
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command.merge!(BSON::OrderedHash["limit", @limit]) if @limit != 0
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command.merge!(BSON::OrderedHash["skip", @skip]) if @skip != 0
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end
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command.merge!(BSON::OrderedHash["fields", @fields])
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response = @db.command(command)
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return response['n'].to_i if Mongo::Support.ok?(response)
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return 0 if response['errmsg'] == "ns missing"
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raise OperationFailure.new("Count failed: #{response['errmsg']}", response['code'], response)
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end
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# Sort this cursor's results.
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#
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# This method overrides any sort order specified in the Collection#find
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# method, and only the last sort applied has an effect.
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#
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# @param [Symbol, Array] key_or_list either 1) a key to sort by or 2)
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# an array of [key, direction] pairs to sort by. Direction should
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# be specified as Mongo::ASCENDING (or :ascending / :asc) or Mongo::DESCENDING (or :descending / :desc)
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#
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# @raise [InvalidOperation] if this cursor has already been used.
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#
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# @raise [InvalidSortValueError] if the specified order is invalid.
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def sort(key_or_list, direction=nil)
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check_modifiable
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if !direction.nil?
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order = [[key_or_list, direction]]
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else
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order = key_or_list
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end
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@order = order
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self
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end
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# Limit the number of results to be returned by this cursor.
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#
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# This method overrides any limit specified in the Collection#find method,
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# and only the last limit applied has an effect.
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#
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# @return [Integer] the current number_to_return if no parameter is given.
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#
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# @raise [InvalidOperation] if this cursor has already been used.
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#
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# @core limit limit-instance_method
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def limit(number_to_return=nil)
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return @limit unless number_to_return
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check_modifiable
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@limit = number_to_return
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self
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end
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# Skips the first +number_to_skip+ results of this cursor.
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# Returns the current number_to_skip if no parameter is given.
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#
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# This method overrides any skip specified in the Collection#find method,
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# and only the last skip applied has an effect.
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#
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# @return [Integer]
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#
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# @raise [InvalidOperation] if this cursor has already been used.
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def skip(number_to_skip=nil)
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return @skip unless number_to_skip
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check_modifiable
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@skip = number_to_skip
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self
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end
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# Set the batch size for server responses.
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#
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# Note that the batch size will take effect only on queries
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# where the number to be returned is greater than 100.
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#
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# @param [Integer] size either 0 or some integer greater than 1. If 0,
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# the server will determine the batch size.
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#
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# @return [Cursor]
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def batch_size(size=nil)
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return @batch_size unless size
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check_modifiable
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if size < 0 || size == 1
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raise ArgumentError, "Invalid value for batch_size #{size}; must be 0 or > 1."
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else
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@batch_size = @limit != 0 && size > @limit ? @limit : size
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end
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self
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end
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# Iterate over each document in this cursor, yielding it to the given
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# block.
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#
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# Iterating over an entire cursor will close it.
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#
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# @yield passes each document to a block for processing.
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#
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# @example if 'comments' represents a collection of comments:
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# comments.find.each do |doc|
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# puts doc['user']
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# end
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def each
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while doc = self.next
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yield doc
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end
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end
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# Receive all the documents from this cursor as an array of hashes.
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#
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# Notes:
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#
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# If you've already started iterating over the cursor, the array returned
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# by this method contains only the remaining documents. See Cursor#rewind! if you
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# need to reset the cursor.
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#
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# Use of this method is discouraged - in most cases, it's much more
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# efficient to retrieve documents as you need them by iterating over the cursor.
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#
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# @return [Array] an array of documents.
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def to_a
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super
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end
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# Get the explain plan for this cursor.
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#
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# @return [Hash] a document containing the explain plan for this cursor.
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#
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# @core explain explain-instance_method
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def explain
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c = Cursor.new(@collection,
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query_options_hash.merge(:limit => -@limit.abs, :explain => true))
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explanation = c.next_document
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c.close
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explanation
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end
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# Close the cursor.
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#
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# Note: if a cursor is read until exhausted (read until Mongo::Constants::OP_QUERY or
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# Mongo::Constants::OP_GETMORE returns zero for the cursor id), there is no need to
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# close it manually.
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#
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# Note also: Collection#find takes an optional block argument which can be used to
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# ensure that your cursors get closed.
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#
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# @return [True]
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def close
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if @cursor_id && @cursor_id != 0
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message = BSON::ByteBuffer.new([0, 0, 0, 0])
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message.put_int(1)
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message.put_long(@cursor_id)
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log(:debug, "Cursor#close #{@cursor_id}")
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@connection.send_message(Mongo::Constants::OP_KILL_CURSORS, message, :connection => :reader)
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end
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@cursor_id = 0
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@closed = true
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end
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# Is this cursor closed?
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#
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# @return [Boolean]
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def closed?
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@closed
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end
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# Returns an integer indicating which query options have been selected.
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#
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# @return [Integer]
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#
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# @see http://www.mongodb.org/display/DOCS/Mongo+Wire+Protocol#MongoWireProtocol-Mongo::Constants::OPQUERY
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# The MongoDB wire protocol.
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def query_opts
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warn "The method Cursor#query_opts has been deprecated " +
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"and will removed in v2.0. Use Cursor#options instead."
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@options
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end
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# Add an option to the query options bitfield.
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#
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# @param opt a valid query option
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#
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# @raise InvalidOperation if this method is run after the cursor has bee
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# iterated for the first time.
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#
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# @return [Integer] the current value of the options bitfield for this cursor.
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#
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# @see http://www.mongodb.org/display/DOCS/Mongo+Wire+Protocol#MongoWireProtocol-Mongo::Constants::OPQUERY
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def add_option(opt)
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check_modifiable
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@options |= opt
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@options
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end
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# Remove an option from the query options bitfield.
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#
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# @param opt a valid query option
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#
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# @raise InvalidOperation if this method is run after the cursor has bee
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# iterated for the first time.
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#
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# @return [Integer] the current value of the options bitfield for this cursor.
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#
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# @see http://www.mongodb.org/display/DOCS/Mongo+Wire+Protocol#MongoWireProtocol-Mongo::Constants::OPQUERY
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def remove_option(opt)
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check_modifiable
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@options &= ~opt
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@options
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end
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# Get the query options for this Cursor.
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#
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# @return [Hash]
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def query_options_hash
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{ :selector => @selector,
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:fields => @fields,
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:skip => @skip,
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:limit => @limit,
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:order => @order,
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:hint => @hint,
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:snapshot => @snapshot,
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:timeout => @timeout,
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:max_scan => @max_scan,
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:return_key => @return_key,
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:show_disk_loc => @show_disk_loc }
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end
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# Clean output for inspect.
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def inspect
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"<Mongo::Cursor:0x#{object_id.to_s(16)} namespace='#{@db.name}.#{@collection.name}' " +
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"@selector=#{@selector.inspect} @cursor_id=#{@cursor_id}>"
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end
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private
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# Convert the +:fields+ parameter from a single field name or an array
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# of fields names to a hash, with the field names for keys and '1' for each
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# value.
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def convert_fields_for_query(fields)
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case fields
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when String, Symbol
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{fields => 1}
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when Array
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return nil if fields.length.zero?
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fields.each_with_object({}) { |field, hash| hash[field] = 1 }
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when Hash
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return fields
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end
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end
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# Return the number of documents remaining for this cursor.
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def num_remaining
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if @cache.length == 0
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if @query_run && (@options & OP_QUERY_EXHAUST != 0)
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close
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return 0
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else
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refresh
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end
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end
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@cache.length
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end
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# Refresh the documents in @cache. This means either
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# sending the initial query or sending a GET_MORE operation.
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def refresh
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if !@query_run
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send_initial_query
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elsif !@cursor_id.zero?
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send_get_more
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end
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end
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def send_initial_query
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message = construct_query_message
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sock = @socket || checkout_socket_from_connection
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instrument(:find, instrument_payload) do
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begin
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results, @n_received, @cursor_id = @connection.receive_message(
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Mongo::Constants::OP_QUERY, message, nil, sock, @command,
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nil, @options & OP_QUERY_EXHAUST != 0)
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rescue ConnectionFailure, OperationFailure, OperationTimeout => ex
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force_checkin_socket(sock)
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raise ex
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end
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checkin_socket(sock) unless @socket
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@returned += @n_received
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@cache += results
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@query_run = true
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close_cursor_if_query_complete
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end
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end
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def send_get_more
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message = BSON::ByteBuffer.new([0, 0, 0, 0])
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# DB name.
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BSON::BSON_RUBY.serialize_cstr(message, "#{@db.name}.#{@collection.name}")
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# Number of results to return.
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if @limit > 0
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limit = @limit - @returned
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if @batch_size > 0
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limit = limit < @batch_size ? limit : @batch_size
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end
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message.put_int(limit)
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else
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message.put_int(@batch_size)
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end
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# Cursor id.
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message.put_long(@cursor_id)
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log(:debug, "cursor.refresh() for cursor #{@cursor_id}") if @logger
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sock = @socket || checkout_socket_for_op_get_more
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begin
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results, @n_received, @cursor_id = @connection.receive_message(
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Mongo::Constants::OP_GET_MORE, message, nil, sock, @command, nil)
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rescue ConnectionFailure, OperationFailure, OperationTimeout => ex
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force_checkin_socket(sock)
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raise ex
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end
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checkin_socket(sock) unless @socket
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@returned += @n_received
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@cache += results
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close_cursor_if_query_complete
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end
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def checkout_socket_from_connection
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socket = nil
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begin
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@checkin_connection = true
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if @command || @read_preference == :primary
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socket = @connection.checkout_writer
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else
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@read_pool = @connection.read_pool
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socket = @connection.checkout_reader
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end
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rescue SystemStackError, NoMemoryError, SystemCallError => ex
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@connection.close
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raise ex
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end
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socket
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end
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def checkout_socket_for_op_get_more
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if @read_pool && (@read_pool != @connection.read_pool)
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checkout_socket_from_read_pool
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else
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checkout_socket_from_connection
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end
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end
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def checkout_socket_from_read_pool
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new_pool = @connection.secondary_pools.detect do |pool|
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pool.host == @read_pool.host && pool.port == @read_pool.port
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end
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if new_pool
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sock = nil
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begin
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@read_pool = new_pool
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sock = new_pool.checkout
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@checkin_read_pool = true
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rescue SystemStackError, NoMemoryError, SystemCallError => ex
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@connection.close
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raise ex
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end
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return sock
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else
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|
raise Mongo::OperationFailure, "Failure to continue iterating " +
|
|
"cursor because the the replica set member persisting this " +
|
|
"cursor at #{@read_pool.host_string} cannot be found."
|
|
end
|
|
end
|
|
|
|
def checkin_socket(sock)
|
|
if @checkin_read_pool
|
|
@read_pool.checkin(sock)
|
|
@checkin_read_pool = false
|
|
elsif @checkin_connection
|
|
if @command || @read_preference == :primary
|
|
@connection.checkin_writer(sock)
|
|
else
|
|
@connection.checkin_reader(sock)
|
|
end
|
|
@checkin_connection = false
|
|
end
|
|
end
|
|
|
|
def force_checkin_socket(sock)
|
|
if @checkin_read_pool
|
|
@read_pool.checkin(sock)
|
|
@checkin_read_pool = false
|
|
else
|
|
if @command || @read_preference == :primary
|
|
@connection.checkin_writer(sock)
|
|
else
|
|
@connection.checkin_reader(sock)
|
|
end
|
|
@checkin_connection = false
|
|
end
|
|
end
|
|
|
|
def construct_query_message
|
|
message = BSON::ByteBuffer.new
|
|
message.put_int(@options)
|
|
BSON::BSON_RUBY.serialize_cstr(message, "#{@db.name}.#{@collection.name}")
|
|
message.put_int(@skip)
|
|
message.put_int(@limit)
|
|
spec = query_contains_special_fields? ? construct_query_spec : @selector
|
|
message.put_binary(BSON::BSON_CODER.serialize(spec, false).to_s)
|
|
message.put_binary(BSON::BSON_CODER.serialize(@fields, false).to_s) if @fields
|
|
message
|
|
end
|
|
|
|
def instrument_payload
|
|
log = { :database => @db.name, :collection => @collection.name, :selector => selector }
|
|
log[:fields] = @fields if @fields
|
|
log[:skip] = @skip if @skip && (@skip != 0)
|
|
log[:limit] = @limit if @limit && (@limit != 0)
|
|
log[:order] = @order if @order
|
|
log
|
|
end
|
|
|
|
def construct_query_spec
|
|
return @selector if @selector.has_key?('$query')
|
|
spec = BSON::OrderedHash.new
|
|
spec['$query'] = @selector
|
|
spec['$orderby'] = Mongo::Support.format_order_clause(@order) if @order
|
|
spec['$hint'] = @hint if @hint && @hint.length > 0
|
|
spec['$explain'] = true if @explain
|
|
spec['$snapshot'] = true if @snapshot
|
|
spec['$maxScan'] = @max_scan if @max_scan
|
|
spec['$returnKey'] = true if @return_key
|
|
spec['$showDiskLoc'] = true if @show_disk_loc
|
|
spec
|
|
end
|
|
|
|
# Returns true if the query contains order, explain, hint, or snapshot.
|
|
def query_contains_special_fields?
|
|
@order || @explain || @hint || @snapshot || @show_disk_loc ||
|
|
@max_scan || @return_key
|
|
end
|
|
|
|
def close_cursor_if_query_complete
|
|
if @limit > 0 && @returned >= @limit
|
|
close
|
|
end
|
|
end
|
|
|
|
def check_modifiable
|
|
if @query_run || @closed
|
|
raise InvalidOperation, "Cannot modify the query once it has been run or closed."
|
|
end
|
|
end
|
|
end
|
|
end
|