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

231 lines
7.6 KiB
Ruby
Raw Normal View History

2008-12-17 16:49:06 +00:00
# --
2009-01-06 15:51:01 +00:00
# Copyright (C) 2008-2009 10gen Inc.
2008-11-22 01:00:51 +00:00
#
# This program is free software: you can redistribute it and/or modify it
# under the terms of the GNU Affero General Public License, version 3, as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License
# for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
2008-12-17 16:49:06 +00:00
# ++
2008-11-22 01:00:51 +00:00
require 'mongo/message'
require 'mongo/util/byte_buffer'
require 'mongo/util/bson'
module XGen
module Mongo
module Driver
2008-12-17 16:43:08 +00:00
# A cursor over query results. Returned objects are hashes.
2008-11-22 01:00:51 +00:00
class Cursor
include Enumerable
RESPONSE_HEADER_SIZE = 20
2009-01-13 20:51:41 +00:00
attr_reader :db, :collection, :query
2009-01-13 20:51:41 +00:00
def initialize(db, collection, query)
@db, @collection, @query = db, collection, query
@num_to_return = @query.number_to_return || 0
@cache = []
2008-11-22 01:00:51 +00:00
@closed = false
@can_call_to_a = true
@query_run = false
2008-11-22 01:00:51 +00:00
end
def closed?; @closed; end
2009-01-13 20:51:41 +00:00
# Set hint fields to use and return +self+. hint_fields may be a
2009-01-14 15:28:32 +00:00
# single field name, array of field names, or a hash whose keys will
# become the hint field names. May be +nil+. If no hint fields are
# specified, the ones in the collection are used if they exist.
2009-01-13 20:51:41 +00:00
def hint(hint_fields)
2009-01-14 15:28:32 +00:00
@hint_fields = case hint_fields
when String
[hint_fields]
when Hash
hint_fields.keys
when nil
nil
else
hint_fields.to_a
end
2009-01-13 20:51:41 +00:00
self
end
# Return +true+ if there are more records to retrieve. We do not check
# @num_to_return; #each is responsible for doing that.
2008-11-22 01:00:51 +00:00
def more?
num_remaining > 0
end
2008-12-17 16:43:08 +00:00
# Return the next object. Raises an error if necessary.
2008-11-22 01:00:51 +00:00
def next_object
refill_via_get_more if num_remaining == 0
o = @cache.shift
2008-12-09 19:47:34 +00:00
raise o['$err'] if o['$err']
o
2008-11-22 01:00:51 +00:00
end
# Iterate over each object, yielding it to the given block. At most
# @num_to_return records are returned (or all of them, if
# @num_to_return is 0).
#
# If #to_a has already been called then this method uses the array
# that we store internally. In that case, #each can be called multiple
# times because it re-uses that array.
#
# You can call #each after calling #to_a (multiple times even, because
# it will use the internally-stored array), but you can't call #to_a
# after calling #each unless you also called it before calling #each.
# If you try to do that, an error will be raised.
2008-11-22 01:00:51 +00:00
def each
if @rows # Already turned into an array
@rows.each { |row| yield row }
else
num_returned = 0
while more? && (@num_to_return <= 0 || num_returned < @num_to_return)
yield next_object()
num_returned += 1
end
@can_call_to_a = false
end
end
# Return all of the rows (up to the +num_to_return+ value specified in
# #new) as an array. Calling this multiple times will work fine; it
# always returns the same array.
#
# Don't use this if you're expecting large amounts of data, of course.
# All of the returned rows are kept in an array stored in this object
# so it can be reused.
#
# You can call #each after calling #to_a (multiple times even, because
# it will use the internally-stored array), but you can't call #to_a
# after calling #each unless you also called it before calling #each.
# If you try to do that, an error will be raised.
def to_a
return @rows if @rows
raise "can't call Cursor#to_a after calling Cursor#each" unless @can_call_to_a
@rows = []
num_returned = 0
while more? && (@num_to_return <= 0 || num_returned < @num_to_return)
@rows << next_object()
num_returned += 1
2008-11-22 01:00:51 +00:00
end
@rows
2008-11-22 01:00:51 +00:00
end
# Returns an explain plan record.
def explain
2009-01-14 15:42:56 +00:00
old_val = @query.explain
@query.explain = true
c = Cursor.new(@db, @collection, @query)
explanation = c.next_object
c.close
2009-01-14 15:42:56 +00:00
@query.explain = old_val
explanation
end
2008-12-17 16:43:08 +00:00
# Close the cursor.
2008-11-22 01:00:51 +00:00
def close
@db.send_to_db(KillCursorsMessage.new(@cursor_id)) if @cursor_id
@cache = []
2008-11-22 01:00:51 +00:00
@cursor_id = 0
@closed = true
end
protected
def read_all
read_message_header
read_response_header
read_objects_off_wire
end
def read_objects_off_wire
while doc = next_object_on_wire
@cache << doc
2008-11-22 01:00:51 +00:00
end
end
def read_message_header
MessageHeader.new.read_header(@db.socket)
end
def read_response_header
header_buf = ByteBuffer.new
header_buf.put_array(@db.socket.recv(RESPONSE_HEADER_SIZE).unpack("C*"))
raise "Short read for DB response header; expected #{RESPONSE_HEADER_SIZE} bytes, saw #{header_buf.length}" unless header_buf.length == RESPONSE_HEADER_SIZE
header_buf.rewind
@result_flags = header_buf.get_int
@cursor_id = header_buf.get_long
@starting_from = header_buf.get_int
@n_returned = header_buf.get_int
@n_remaining = @n_returned
end
def num_remaining
refill_via_get_more if @cache.length == 0
@cache.length
2008-11-22 01:00:51 +00:00
end
private
def next_object_on_wire
send_query_if_needed
2008-11-22 01:00:51 +00:00
# if @n_remaining is 0 but we have a non-zero cursor, there are more
# to fetch, so do a GetMore operation, but don't do it here - do it
# when someone pulls an object out of the cache and it's empty
return nil if @n_remaining == 0
object_from_stream
end
def refill_via_get_more
send_query_if_needed
2008-11-22 01:00:51 +00:00
return if @cursor_id == 0
@db.send_to_db(GetMoreMessage.new(@db.name, @collection.name, @cursor_id))
2008-11-22 01:00:51 +00:00
read_all
end
def object_from_stream
buf = ByteBuffer.new
buf.put_array(@db.socket.recv(4).unpack("C*"))
buf.rewind
size = buf.get_int
buf.put_array(@db.socket.recv(size-4).unpack("C*"), 4)
@n_remaining -= 1
buf.rewind
BSON.new(@db).deserialize(buf)
2008-11-22 01:00:51 +00:00
end
def send_query_if_needed
# Run query first time we request an object from the wire
unless @query_run
2009-01-13 20:51:41 +00:00
hints = @hint_fields || @collection.hint_fields
2009-01-14 15:42:56 +00:00
old_hints = @query.hint_fields
@query.hint_fields = hints
@db.send_query_message(QueryMessage.new(@db.name, @collection.name, @query))
@query_run = true
2009-01-14 15:42:56 +00:00
@query.hint_fields = old_hints
read_all
end
end
2008-11-22 01:00:51 +00:00
def to_s
"DBResponse(flags=#@result_flags, cursor_id=#@cursor_id, start=#@starting_from, n_returned=#@n_returned)"
end
end
end
end
end