mongo-ruby-driver/lib/mongo/cursor.rb

654 lines
19 KiB
Ruby

# encoding: UTF-8
# Copyright (C) 2008-2011 10gen Inc.
#
# 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
# A cursor over query results. Returned objects are hashes.
class Cursor
include Enumerable
include Mongo::Constants
include Mongo::Conversions
include Mongo::Logging
attr_reader :collection, :selector, :fields,
:order, :hint, :snapshot, :timeout,
:full_collection_name, :transformer,
:options, :cursor_id, :show_disk_loc
# 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
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 $query
@order = opts[:order]
@explain = opts[:explain]
@hint = opts[:hint]
@snapshot = opts[:snapshot]
@max_scan = opts.fetch(:max_scan, nil)
@return_key = opts.fetch(:return_key, nil)
@show_disk_loc = opts.fetch(:show_disk_loc, nil)
# Wire-protocol settings
@fields = convert_fields_for_query(opts[:fields])
@skip = opts[:skip] || 0
@limit = opts[:limit] || 0
@tailable = opts[:tailable] || false
@timeout = opts.fetch(:timeout, true)
@options = 0
# Use this socket for the query
@socket = opts[:socket]
@closed = false
@query_run = false
@transformer = opts[:transformer]
if value = opts[:read]
Mongo::Support.validate_read_preference(value)
else
value = collection.read_preference
end
@read_preference = value.is_a?(Hash) ? value.dup : value
batch_size(opts[:batch_size] || 0)
@full_collection_name = "#{@collection.db.name}.#{@collection.name}"
@cache = []
@returned = 0
if(!@timeout)
add_option(OP_QUERY_NO_CURSOR_TIMEOUT)
end
if(@read_preference != :primary)
add_option(OP_QUERY_SLAVE_OK)
end
if(@tailable)
add_option(OP_QUERY_TAILABLE)
end
if @collection.name =~ /^\$cmd/ || @collection.name =~ /^system/
@command = true
else
@command = false
end
@checkin_read_pool = false
@checkin_connection = false
@read_pool = nil
end
# Guess whether the cursor is alive on the server.
#
# Note that this method only checks whether we have
# a cursor id. The cursor may still have timed out
# on the server. This will be indicated in the next
# call to Cursor#next.
#
# @return [Boolean]
def alive?
@cursor_id && @cursor_id != 0
end
# Get the next document specified the cursor options.
#
# @return [Hash, Nil] the next document or Nil if no documents remain.
def next
if @cache.length == 0
if @query_run && (@options & OP_QUERY_EXHAUST != 0)
close
return nil
else
refresh
end
end
doc = @cache.shift
if doc && doc['$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
alias :next_document :next
# Reset this cursor on the server. Cursor options, such as the
# query string and the values for skip and limit, are preserved.
def rewind!
close
@cache.clear
@cursor_id = nil
@closed = false
@query_run = false
@n_received = nil
true
end
# Determine whether this cursor has any remaining results.
#
# @return [Boolean]
def has_next?
num_remaining > 0
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.
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
# 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 or 2)
# an array of [key, 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.
def sort(key_or_list, direction=nil)
check_modifiable
if !direction.nil?
order = [[key_or_list, direction]]
else
order = key_or_list
end
@order = order
self
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
def limit(number_to_return=nil)
return @limit unless number_to_return
check_modifiable
@limit = number_to_return
self
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.
def skip(number_to_skip=nil)
return @skip unless number_to_skip
check_modifiable
@skip = number_to_skip
self
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]
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
# 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
def each
while doc = self.next
yield doc
end
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.
def to_a
super
end
# Get the explain plan for this cursor.
#
# @return [Hash] a document containing the explain plan for this cursor.
#
# @core explain explain-instance_method
def explain
c = Cursor.new(@collection,
query_options_hash.merge(:limit => -@limit.abs, :explain => true))
explanation = c.next_document
c.close
explanation
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]
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
# Is this cursor closed?
#
# @return [Boolean]
def closed?
@closed
end
# Returns an integer indicating which query options have been selected.
#
# @return [Integer]
#
# @see http://www.mongodb.org/display/DOCS/Mongo+Wire+Protocol#MongoWireProtocol-Mongo::Constants::OPQUERY
# The MongoDB wire protocol.
def query_opts
warn "The method Cursor#query_opts has been deprecated " +
"and will removed in v2.0. Use Cursor#options instead."
@options
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 http://www.mongodb.org/display/DOCS/Mongo+Wire+Protocol#MongoWireProtocol-Mongo::Constants::OPQUERY
def add_option(opt)
check_modifiable
@options |= opt
@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 http://www.mongodb.org/display/DOCS/Mongo+Wire+Protocol#MongoWireProtocol-Mongo::Constants::OPQUERY
def remove_option(opt)
check_modifiable
@options &= ~opt
@options
end
# Get the query options for this Cursor.
#
# @return [Hash]
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
# Clean output for inspect.
def inspect
"<Mongo::Cursor:0x#{object_id.to_s(16)} namespace='#{@db.name}.#{@collection.name}' " +
"@selector=#{@selector.inspect} @cursor_id=#{@cursor_id}>"
end
private
# Convert the +:fields+ parameter from a single field name or an array
# of fields names to a hash, with the field names for keys and '1' for each
# value.
def convert_fields_for_query(fields)
case fields
when String, Symbol
{fields => 1}
when Array
return nil if fields.length.zero?
fields.each_with_object({}) { |field, hash| hash[field] = 1 }
when Hash
return fields
end
end
# Return the number of documents remaining for this cursor.
def num_remaining
if @cache.length == 0
if @query_run && (@options & OP_QUERY_EXHAUST != 0)
close
return 0
else
refresh
end
end
@cache.length
end
# Refresh the documents in @cache. This means either
# sending the initial query or sending a GET_MORE operation.
def refresh
if !@query_run
send_initial_query
elsif !@cursor_id.zero?
send_get_more
end
end
def send_initial_query
message = construct_query_message
sock = @socket || checkout_socket_from_connection
instrument(:find, instrument_payload) do
begin
results, @n_received, @cursor_id = @connection.receive_message(
Mongo::Constants::OP_QUERY, message, nil, sock, @command,
nil, @options & OP_QUERY_EXHAUST != 0)
rescue ConnectionFailure, OperationFailure, OperationTimeout => ex
force_checkin_socket(sock) unless @socket
raise ex
end
checkin_socket(sock) unless @socket
@returned += @n_received
@cache += results
@query_run = true
close_cursor_if_query_complete
end
end
def send_get_more
message = BSON::ByteBuffer.new([0, 0, 0, 0])
# DB name.
BSON::BSON_RUBY.serialize_cstr(message, "#{@db.name}.#{@collection.name}")
# Number of results to return.
if @limit > 0
limit = @limit - @returned
if @batch_size > 0
limit = limit < @batch_size ? limit : @batch_size
end
message.put_int(limit)
else
message.put_int(@batch_size)
end
# Cursor id.
message.put_long(@cursor_id)
log(:debug, "cursor.refresh() for cursor #{@cursor_id}") if @logger
sock = @socket || checkout_socket_for_op_get_more
begin
results, @n_received, @cursor_id = @connection.receive_message(
Mongo::Constants::OP_GET_MORE, message, nil, sock, @command, nil)
rescue ConnectionFailure, OperationFailure, OperationTimeout => ex
force_checkin_socket(sock)
raise ex
end
checkin_socket(sock) unless @socket
@returned += @n_received
@cache += results
close_cursor_if_query_complete
end
def checkout_socket_from_connection
socket = nil
begin
@checkin_connection = true
if @command || @read_preference == :primary
socket = @connection.checkout_writer
elsif @read_preference == :secondary_only
socket = @connection.checkout_secondary
else
@read_pool = @connection.read_pool
socket = @connection.checkout_reader
end
rescue SystemStackError, NoMemoryError, SystemCallError => ex
@connection.close
raise ex
end
socket
end
def checkout_socket_for_op_get_more
if @read_pool && (@read_pool != @connection.read_pool)
checkout_socket_from_read_pool
else
checkout_socket_from_connection
end
end
def checkout_socket_from_read_pool
new_pool = @connection.secondary_pools.detect do |pool|
pool.host == @read_pool.host && pool.port == @read_pool.port
end
if new_pool
sock = nil
begin
@read_pool = new_pool
sock = new_pool.checkout
@checkin_read_pool = true
rescue SystemStackError, NoMemoryError, SystemCallError => ex
@connection.close
raise ex
end
return sock
else
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