Class | Mongo::Cursor |
In: |
lib/mongo/cursor.rb
|
Parent: | Object |
A cursor over query results. Returned objects are hashes.
collection | [R] | |
cursor_id | [R] | |
fields | [R] | |
full_collection_name | [R] | |
hint | [R] | |
options | [R] | |
order | [R] | |
selector | [R] | |
show_disk_loc | [R] | |
snapshot | [R] | |
timeout | [R] | |
transformer | [R] |
Create a new cursor.
Note: cursors are created when executing queries using [Collection#find] and other similar methods. Application developers shouldn‘t have to create cursors manually.
@return [Cursor]
@core cursors constructor_details
# File lib/mongo/cursor.rb, line 39 def initialize(collection, opts={}) @cursor_id = nil @db = collection.db @collection = collection @connection = @db.connection @logger = @connection.logger # Query selector @selector = opts[:selector] || {} # Special operators that form part of $query @order = opts[:order] @explain = opts[:explain] @hint = opts[:hint] @snapshot = opts[:snapshot] @max_scan = opts.fetch(:max_scan, nil) @return_key = opts.fetch(:return_key, nil) @show_disk_loc = opts.fetch(:show_disk_loc, nil) # Wire-protocol settings @fields = convert_fields_for_query(opts[:fields]) @skip = opts[:skip] || 0 @limit = opts[:limit] || 0 @tailable = opts[:tailable] || false @timeout = opts.fetch(:timeout, true) @options = 0 # Use this socket for the query @socket = opts[:socket] @closed = false @query_run = false @transformer = opts[:transformer] if value = opts[:read] Mongo::Support.validate_read_preference(value) else value = collection.read_preference end @read_preference = value.is_a?(Hash) ? value.dup : value batch_size(opts[:batch_size] || 0) @full_collection_name = "#{@collection.db.name}.#{@collection.name}" @cache = [] @returned = 0 if(!@timeout) add_option(OP_QUERY_NO_CURSOR_TIMEOUT) end if(@read_preference != :primary) add_option(OP_QUERY_SLAVE_OK) end if(@tailable) add_option(OP_QUERY_TAILABLE) end if @collection.name =~ /^\$cmd/ || @collection.name =~ /^system/ @command = true else @command = false end @checkin_read_pool = false @checkin_connection = false @read_pool = nil end
Add an option to the query options bitfield.
@param opt a valid query option
@raise InvalidOperation if this method is run after the cursor has bee
iterated for the first time.
@return [Integer] the current value of the options bitfield for this cursor.
@see www.mongodb.org/display/DOCS/Mongo+Wire+Protocol#MongoWireProtocol-Mongo::Constants::OPQUERY
# File lib/mongo/cursor.rb, line 377 def add_option(opt) check_modifiable @options |= opt @options end
Guess whether the cursor is alive on the server.
Note that this method only checks whether we have a cursor id. The cursor may still have timed out on the server. This will be indicated in the next call to Cursor#next.
@return [Boolean]
# File lib/mongo/cursor.rb, line 115 def alive? @cursor_id && @cursor_id != 0 end
Set the batch size for server responses.
Note that the batch size will take effect only on queries where the number to be returned is greater than 100.
This can not override MongoDB‘s limit on the amount of data it will return to the client. Depending on server version this can be 4-16mb.
@param [Integer] size either 0 or some integer greater than 1. If 0,
the server will determine the batch size.
@return [Cursor]
# File lib/mongo/cursor.rb, line 267 def batch_size(size=nil) return @batch_size unless size check_modifiable if size < 0 || size == 1 raise ArgumentError, "Invalid value for batch_size #{size}; must be 0 or > 1." else @batch_size = @limit != 0 && size > @limit ? @limit : size end self end
Close the cursor.
Note: if a cursor is read until exhausted (read until Mongo::Constants::OP_QUERY or Mongo::Constants::OP_GETMORE returns zero for the cursor id), there is no need to close it manually.
Note also: Collection#find takes an optional block argument which can be used to ensure that your cursors get closed.
@return [True]
# File lib/mongo/cursor.rb, line 336 def close if @cursor_id && @cursor_id != 0 message = BSON::ByteBuffer.new([0, 0, 0, 0]) message.put_int(1) message.put_long(@cursor_id) log(:debug, "Cursor#close #{@cursor_id}") @connection.send_message(Mongo::Constants::OP_KILL_CURSORS, message, :connection => :reader) end @cursor_id = 0 @closed = true end
Get the size of the result set for this query.
@param [Boolean] whether of not to take notice of skip and limit
@return [Integer] the number of objects in the result set for this query.
@raise [OperationFailure] on a database error.
# File lib/mongo/cursor.rb, line 181 def count(skip_and_limit = false) command = BSON::OrderedHash["count", @collection.name, "query", @selector] if skip_and_limit command.merge!(BSON::OrderedHash["limit", @limit]) if @limit != 0 command.merge!(BSON::OrderedHash["skip", @skip]) if @skip != 0 end command.merge!(BSON::OrderedHash["fields", @fields]) response = @db.command(command) return response['n'].to_i if Mongo::Support.ok?(response) return 0 if response['errmsg'] == "ns missing" raise OperationFailure.new("Count failed: #{response['errmsg']}", response['code'], response) end
Iterate over each document in this cursor, yielding it to the given block.
Iterating over an entire cursor will close it.
@yield passes each document to a block for processing.
@example if ‘comments’ represents a collection of comments:
comments.find.each do |doc| puts doc['user'] end
# File lib/mongo/cursor.rb, line 290 def each while doc = self.next yield doc end end
Get the explain plan for this cursor.
@return [Hash] a document containing the explain plan for this cursor.
@core explain explain-instance_method
# File lib/mongo/cursor.rb, line 317 def explain c = Cursor.new(@collection, query_options_hash.merge(:limit => -@limit.abs, :explain => true)) explanation = c.next_document c.close explanation end
Determine whether this cursor has any remaining results.
@return [Boolean]
# File lib/mongo/cursor.rb, line 170 def has_next? num_remaining > 0 end
Limit the number of results to be returned by this cursor.
This method overrides any limit specified in the Collection#find method, and only the last limit applied has an effect.
@return [Integer] the current number_to_return if no parameter is given.
@raise [InvalidOperation] if this cursor has already been used.
@core limit limit-instance_method
# File lib/mongo/cursor.rb, line 230 def limit(number_to_return=nil) return @limit unless number_to_return check_modifiable @limit = number_to_return self end
Get the next document specified the cursor options.
@return [Hash, Nil] the next document or Nil if no documents remain.
# File lib/mongo/cursor.rb, line 122 def next if @cache.length == 0 if @query_run && (@options & OP_QUERY_EXHAUST != 0) close return nil else refresh end end doc = @cache.shift if doc && doc['$err'] err = doc['$err'] # If the server has stopped being the master (e.g., it's one of a # pair but it has died or something like that) then we close that # connection. The next request will re-open on master server. if err.include?("not master") @connection.close raise ConnectionFailure.new(err, doc['code'], doc) end raise OperationFailure.new(err, doc['code'], doc) end if @transformer.nil? doc else @transformer.call(doc) if doc end end
Get the query options for this Cursor.
@return [Hash]
# File lib/mongo/cursor.rb, line 404 def query_options_hash { :selector => @selector, :fields => @fields, :skip => @skip, :limit => @limit, :order => @order, :hint => @hint, :snapshot => @snapshot, :timeout => @timeout, :max_scan => @max_scan, :return_key => @return_key, :show_disk_loc => @show_disk_loc } end
Returns an integer indicating which query options have been selected.
@return [Integer]
@see www.mongodb.org/display/DOCS/Mongo+Wire+Protocol#MongoWireProtocol-Mongo::Constants::OPQUERY The MongoDB wire protocol.
# File lib/mongo/cursor.rb, line 361 def query_opts warn "The method Cursor#query_opts has been deprecated " + "and will removed in v2.0. Use Cursor#options instead." @options end
Remove an option from the query options bitfield.
@param opt a valid query option
@raise InvalidOperation if this method is run after the cursor has bee
iterated for the first time.
@return [Integer] the current value of the options bitfield for this cursor.
@see www.mongodb.org/display/DOCS/Mongo+Wire+Protocol#MongoWireProtocol-Mongo::Constants::OPQUERY
# File lib/mongo/cursor.rb, line 394 def remove_option(opt) check_modifiable @options &= ~opt @options end
Skips the first number_to_skip results of this cursor. Returns the current number_to_skip if no parameter is given.
This method overrides any skip specified in the Collection#find method, and only the last skip applied has an effect.
@return [Integer]
@raise [InvalidOperation] if this cursor has already been used.
# File lib/mongo/cursor.rb, line 247 def skip(number_to_skip=nil) return @skip unless number_to_skip check_modifiable @skip = number_to_skip self end
Sort this cursor‘s results.
This method overrides any sort order specified in the Collection#find method, and only the last sort applied has an effect.
@param [Symbol, Array] key_or_list either 1) a key to sort by 2)
an array of [key, direction] pairs to sort by or 3) a hash of field => direction pairs to sort by. Direction should be specified as Mongo::ASCENDING (or :ascending / :asc) or Mongo::DESCENDING (or :descending / :desc)
@raise [InvalidOperation] if this cursor has already been used.
@raise [InvalidSortValueError] if the specified order is invalid.
# File lib/mongo/cursor.rb, line 211 def sort(order, direction=nil) check_modifiable order = [[order, direction]] unless direction.nil? @order = order self end
Receive all the documents from this cursor as an array of hashes.
Notes:
If you‘ve already started iterating over the cursor, the array returned by this method contains only the remaining documents. See Cursor#rewind! if you need to reset the cursor.
Use of this method is discouraged - in most cases, it‘s much more efficient to retrieve documents as you need them by iterating over the cursor.
@return [Array] an array of documents.
# File lib/mongo/cursor.rb, line 308 def to_a super end