434 lines
14 KiB
Ruby
434 lines
14 KiB
Ruby
# Copyright (C) 2008-2009 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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require 'mongo/util/byte_buffer'
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require 'mongo/util/bson'
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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 Mongo::Conversions
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include Enumerable
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RESPONSE_HEADER_SIZE = 20
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attr_reader :collection, :selector, :admin, :fields,
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:order, :hint, :snapshot, :timeout,
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:full_collection_name
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# Create a new cursor.
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#
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# Should not be called directly by application developers.
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def initialize(collection, options={})
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@db = collection.db
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@collection = collection
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@selector = convert_selector_for_query(options[:selector])
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@fields = convert_fields_for_query(options[:fields])
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@admin = options[:admin] || false
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@skip = options[:skip] || 0
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@limit = options[:limit] || 0
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@order = options[:order]
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@hint = options[:hint]
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@snapshot = options[:snapshot]
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@timeout = options[:timeout] || false
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@explain = options[:explain]
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@full_collection_name = "#{@collection.db.name}.#{@collection.name}"
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@cache = []
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@closed = false
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@query_run = false
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end
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# Return the next object or nil if there are no more. Raises an error
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# if necessary.
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def next_object
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refill_via_get_more if num_remaining == 0
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o = @cache.shift
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if o && o['$err']
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err = o['$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. If the db has auto connect option and a pair of
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# servers, next request will re-open on master server.
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@db.close if err == "not master"
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raise err
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end
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o
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end
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# Get the size of the results set for this query.
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#
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# Returns the number of objects in the results set for this query. Does
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# not take limit and skip into account. Raises OperationFailure on a
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# database error.
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def count
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command = OrderedHash["count", @collection.name,
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"query", @selector,
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"fields", @fields]
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response = @db.db_command(command)
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return response['n'].to_i if response['ok'] == 1
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return 0 if response['errmsg'] == "ns missing"
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raise OperationFailure, "Count failed: #{response['errmsg']}"
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end
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# Sort this cursor's result
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#
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# Takes either a single key and a direction, or an array of [key,
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# direction] pairs. Directions should be specified as Mongo::ASCENDING
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# or Mongo::DESCENDING (or :ascending or :descending) (or :asc or :desc).
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#
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# Raises InvalidOperation if this cursor has already been used. Raises
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# InvalidSortValueError if specified order is invalid.
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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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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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# Limits the number of results to be returned by this cursor.
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# Returns the current number_to_return if no parameter is given.
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#
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# Raises InvalidOperation if this cursor has already been used.
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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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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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raise ArgumentError, "limit requires an integer" unless number_to_return.is_a? Integer
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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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# Raises InvalidOperation if this cursor has already been used.
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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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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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raise ArgumentError, "skip requires an integer" unless number_to_skip.is_a? Integer
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@skip = number_to_skip
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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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def each
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num_returned = 0
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while more? && (@limit <= 0 || num_returned < @limit)
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yield next_object()
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num_returned += 1
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end
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end
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# Return all of the documents in this cursor as an array of hashes.
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#
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# Raises InvalidOperation if this cursor has already been used (including
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# any previous calls to this method).
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#
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# Use of this method is discouraged - iterating over a cursor is much
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# more efficient in most cases.
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def to_a
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raise InvalidOperation, "can't call Cursor#to_a on a used cursor" if @query_run
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rows = []
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num_returned = 0
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while more? && (@limit <= 0 || num_returned < @limit)
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rows << next_object()
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num_returned += 1
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end
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rows
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end
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# Returns an explain plan record for this cursor.
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def explain
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c = Cursor.new(@collection, query_options_hash.merge(:limit => -@limit.abs, :explain => true))
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explanation = c.next_object
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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 by calling this method.
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#
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# Collection#find takes an optional block argument which can be used to
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# ensure that your cursors get closed. See the documentation for
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# Collection#find for details.
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def close
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if @cursor_id
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message = ByteBuffer.new
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message.put_int(0)
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message.put_int(1)
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message.put_long(@cursor_id)
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@db.send_message_with_operation(Mongo::Constants::OP_KILL_CURSORS, message)
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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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# Returns true if this cursor is closed, false otherwise.
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def closed?; @closed; end
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# Returns an integer indicating which query options have been selected.
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# See http://www.mongodb.org/display/DOCS/Mongo+Wire+Protocol#MongoWireProtocol-Mongo::Constants::OPQUERY
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def query_opts
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timeout = @timeout ? 0 : Mongo::Constants::OP_QUERY_NO_CURSOR_TIMEOUT
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slave_ok = @db.slave_ok? ? Mongo::Constants::OP_QUERY_SLAVE_OK : 0
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slave_ok + timeout
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end
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# Returns the query options set on this Cursor.
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def query_options_hash
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{ :selector => @selector,
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:fields => @fields,
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:admin => @admin,
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:skip => @skip_num,
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:limit => @limit_num,
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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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end
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private
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# Converts 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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returning({}) do |hash|
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fields.each { |field| hash[field] = 1 }
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end
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end
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end
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# Set query selector hash. If the selector is a Code or String object,
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# the selector will be used in a $where clause.
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# See http://www.mongodb.org/display/DOCS/Server-side+Code+Execution
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def convert_selector_for_query(selector)
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case selector
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when Hash
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selector
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when nil
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{}
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when String
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{"$where" => Code.new(selector)}
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when Code
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{"$where" => selector}
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end
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end
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# Returns true if the query contains order, explain, hint, or snapshot.
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def query_contains_special_fields?
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@order || @explain || @hint || @snapshot
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end
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def read_all
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read_message_header
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read_response_header
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read_objects_off_wire
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end
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def read_objects_off_wire
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while doc = next_object_on_wire
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@cache << doc
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end
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end
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def read_message_header
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message = ByteBuffer.new
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message.put_array(@db.receive_full(16).unpack("C*"))
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unless message.size == 16 #HEADER_SIZE
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raise "Short read for DB response header: expected #{16} bytes, saw #{message.size}"
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end
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message.rewind
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size = message.get_int
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request_id = message.get_int
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response_to = message.get_int
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op = message.get_int
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end
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def read_response_header
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header_buf = ByteBuffer.new
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header_buf.put_array(@db.receive_full(RESPONSE_HEADER_SIZE).unpack("C*"))
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raise "Short read for DB response header; expected #{RESPONSE_HEADER_SIZE} bytes, saw #{header_buf.length}" unless header_buf.length == RESPONSE_HEADER_SIZE
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header_buf.rewind
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@result_flags = header_buf.get_int
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@cursor_id = header_buf.get_long
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@starting_from = header_buf.get_int
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@n_remaining = header_buf.get_int
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if @n_received
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@n_received += @n_remaining
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else
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@n_received = @n_remaining
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end
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end
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def num_remaining
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refill_via_get_more if @cache.length == 0
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@cache.length
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end
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# Internal method, not for general use. Return +true+ if there are
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# more records to retrieve. This methods does not check @limit;
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# #each is responsible for doing that.
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def more?
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num_remaining > 0
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end
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def next_object_on_wire
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# if @n_remaining is 0 but we have a non-zero cursor, there are more
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# to fetch, so do a GetMore operation, but don't do it here - do it
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# when someone pulls an object out of the cache and it's empty
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return nil if @n_remaining == 0
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object_from_stream
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end
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def refill_via_get_more
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return if send_query_if_needed || @cursor_id.zero?
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@db._synchronize {
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message = ByteBuffer.new
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# Reserved.
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message.put_int(0)
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# DB name.
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db_name = @admin ? 'admin' : @db.name
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BSON.serialize_cstr(message, "#{db_name}.#{@collection.name}")
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# Number of results to return; db decides for now.
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message.put_int(0)
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# Cursor id.
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message.put_long(@cursor_id)
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@db.send_message_with_operation_without_synchronize(Mongo::Constants::OP_GET_MORE, message)
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read_all
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}
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close_cursor_if_query_complete
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end
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def object_from_stream
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buf = ByteBuffer.new
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buf.put_array(@db.receive_full(4).unpack("C*"))
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buf.rewind
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size = buf.get_int
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buf.put_array(@db.receive_full(size - 4).unpack("C*"), 4)
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@n_remaining -= 1
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buf.rewind
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BSON.new.deserialize(buf)
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end
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def send_query_if_needed
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# Run query first time we request an object from the wire
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if @query_run
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false
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else
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message = construct_query_message(@query)
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@db._synchronize {
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@db.send_message_with_operation_without_synchronize(Mongo::Constants::OP_QUERY, message)
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@query_run = true
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read_all
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}
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close_cursor_if_query_complete
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true
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end
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end
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def construct_query_message(query)
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message = ByteBuffer.new
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message.put_int(query_opts)
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db_name = @admin ? 'admin' : @db.name
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BSON.serialize_cstr(message, "#{db_name}.#{@collection.name}")
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message.put_int(@skip)
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message.put_int(@limit)
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selector = @selector
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if query_contains_special_fields?
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selector = selector_with_special_query_fields
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end
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message.put_array(BSON.new.serialize(selector).to_a)
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message.put_array(BSON.new.serialize(@fields).to_a) if @fields
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message
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end
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def selector_with_special_query_fields
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sel = OrderedHash.new
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sel['query'] = @selector
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sel['orderby'] = formatted_order_clause if @order
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sel['$hint'] = @hint if @hint && @hint.length > 0
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sel['$explain'] = true if @explain
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sel['$snapshot'] = true if @snapshot
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sel
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end
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def formatted_order_clause
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case @order
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when String then string_as_sort_parameters(@order)
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when Symbol then symbol_as_sort_parameters(@order)
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when Array then array_as_sort_parameters(@order)
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when Hash # Should be an ordered hash, but this message doesn't care
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warn_if_deprecated(@order)
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@order
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else
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raise InvalidSortValueError, "Illegal order_by, '#{@order.class.name}'; must be String, Array, Hash, or OrderedHash"
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end
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end
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def to_s
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"DBResponse(flags=#@result_flags, cursor_id=#@cursor_id, start=#@starting_from)"
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end
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def close_cursor_if_query_complete
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close if @limit > 0 && @n_received >= @limit
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end
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def check_modifiable
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if @query_run || @closed
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raise InvalidOperation, "Cannot modify the query once it has been run or closed."
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end
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end
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end
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end
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