# Copyright 2014 Google LLC
#
# 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
#
# https://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.
require "delegate"
module Google
module Cloud
module Datastore
class Dataset
##
# QueryResults is a special case Array with additional values.
# A QueryResults object is returned from Dataset#run and contains
# the Entities from the query as well as the query's cursor and
# more_results value.
#
# Please be cautious when treating the QueryResults as an Array.
# Many common Array methods will return a new Array instance.
#
# @example
# require "google/cloud/datastore"
#
# datastore = Google::Cloud::Datastore.new
#
# query = datastore.query("Task")
# tasks = datastore.run query
#
# tasks.size #=> 3
# tasks.cursor.to_s #=> "c2Vjb25kLXBhZ2UtY3Vyc29y"
#
# @example Caution, many Array methods will return a new Array instance:
# require "google/cloud/datastore"
#
# datastore = Google::Cloud::Datastore.new
#
# query = datastore.query("Task")
# tasks = datastore.run query
#
# tasks.size #=> 3
# tasks.cursor.to_s #=> "c2Vjb25kLXBhZ2UtY3Vyc29y"
# descriptions = tasks.map { |t| t["description"] }
# descriptions.size #=> 3
# descriptions.cursor #=> raise NoMethodError
#
class QueryResults < DelegateClass(::Array)
##
# The end_cursor of the QueryResults.
#
# @return [Google::Cloud::Datastore::Cursor]
attr_reader :end_cursor
alias cursor end_cursor
##
# The state of the query after the current batch.
#
# Expected values are:
#
# * `:NOT_FINISHED`
# * `:MORE_RESULTS_AFTER_LIMIT`
# * `:MORE_RESULTS_AFTER_CURSOR`
# * `:NO_MORE_RESULTS`
attr_reader :more_results
##
# @private
attr_accessor :service, :namespace, :cursors, :query
##
# @private
attr_writer :end_cursor, :more_results
##
# Convenience method for determining if the `more_results` value
# is `:NOT_FINISHED`
def not_finished?
more_results == :NOT_FINISHED
end
##
# Convenience method for determining if the `more_results` value
# is `:MORE_RESULTS_AFTER_LIMIT`
def more_after_limit?
more_results == :MORE_RESULTS_AFTER_LIMIT
end
##
# Convenience method for determining if the `more_results` value
# is `:MORE_RESULTS_AFTER_CURSOR`
def more_after_cursor?
more_results == :MORE_RESULTS_AFTER_CURSOR
end
##
# Convenience method for determining if the `more_results` value
# is `:NO_MORE_RESULTS`
def no_more?
more_results == :NO_MORE_RESULTS
end
##
# @private Create a new QueryResults with an array of values.
def initialize arr = []
super arr
end
##
# Whether there are more results available.
#
# @return [Boolean]
#
# @example
# require "google/cloud/datastore"
#
# datastore = Google::Cloud::Datastore.new
#
# query = datastore.query "Task"
# tasks = datastore.run query
#
# if tasks.next?
# next_tasks = tasks.next
# end
#
def next?
not_finished?
end
##
# Retrieve the next page of results.
#
# @return [QueryResults]
#
# @example
# require "google/cloud/datastore"
#
# datastore = Google::Cloud::Datastore.new
#
# query = datastore.query "Task"
# tasks = datastore.run query
#
# if tasks.next?
# next_tasks = tasks.next
# end
#
def next
return nil unless next?
return nil if end_cursor.nil?
ensure_service!
query.start_cursor = cursor.to_grpc # should always be a Cursor...
query.offset = 0 # Never carry an offset across batches
unless query.limit.nil?
# Reduce the limit by the number of entities returned in the current batch
query.limit.value -= count
end
query_res = service.run_query query, namespace
self.class.from_grpc query_res, service, namespace, query
end
##
# Retrieve the {Cursor} for the provided result.
#
# @param [Entity] result The entity object to get a cursor for.
#
# @return [Cursor]
#
# @example
# require "google/cloud/datastore"
#
# datastore = Google::Cloud::Datastore.new
#
# query = datastore.query "Task"
# tasks = datastore.run query
#
# first_task = tasks.first
# first_cursor = tasks.cursor_for first_task
#
def cursor_for result
cursor_index = index result
return nil if cursor_index.nil?
cursors[cursor_index]
end
##
# Calls the given block once for each result and cursor combination,
# which are passed as parameters.
#
# An Enumerator is returned if no block is given.
#
# @yield [result, cursor] The block for accessing each query result
# and cursor.
# @yieldparam [Entity] result The query result object.
# @yieldparam [Cursor] cursor The cursor object.
#
# @return [Enumerator]
#
# @example
# require "google/cloud/datastore"
#
# datastore = Google::Cloud::Datastore.new
#
# query = datastore.query "Task"
# tasks = datastore.run query
# tasks.each_with_cursor do |task, cursor|
# puts "Task #{task.key.id} (#cursor)"
# end
#
def each_with_cursor
return enum_for :each_with_cursor unless block_given?
zip(cursors).each { |r, c| yield [r, c] }
end
##
# Retrieves all query results by repeatedly loading {#next} until
# {#next?} returns `false`. Calls the given block once for each query
# result, which is passed as the parameter.
#
# An Enumerator is returned if no block is given.
#
# This method may make several API calls until all query results are
# retrieved. Be sure to use as narrow a search criteria as possible.
# Please use with caution.
#
# @param [Integer] request_limit The upper limit of API requests to
# make to load all query results. Default is no limit.
# @yield [result] The block for accessing each query result.
# @yieldparam [Entity] result The query result object.
#
# @return [Enumerator]
#
# @example Iterating each query result by passing a block:
# require "google/cloud/datastore"
#
# datastore = Google::Cloud::Datastore.new
#
# query = datastore.query "Task"
# tasks = datastore.run query
# tasks.all do |t|
# puts "Task #{t.key.id} (#cursor)"
# end
#
# @example Using the enumerator by not passing a block:
# require "google/cloud/datastore"
#
# datastore = Google::Cloud::Datastore.new
#
# query = datastore.query "Task"
# tasks = datastore.run query
# tasks.all.map(&:key).each do |key|
# puts "Key #{key.id}"
# end
#
# @example Limit the number of API calls made:
# require "google/cloud/datastore"
#
# datastore = Google::Cloud::Datastore.new
#
# query = datastore.query "Task"
# tasks = datastore.run query
# tasks.all(request_limit: 10) do |t|
# puts "Task #{t.key.id} (#cursor)"
# end
#
def all request_limit: nil, &block
request_limit = request_limit.to_i if request_limit
unless block_given?
return enum_for :all, request_limit: request_limit
end
results = self
loop do
results.each(&block)
if request_limit
request_limit -= 1
break if request_limit.negative?
end
break unless results.next?
results = results.next
end
end
##
# Retrieves all query results and cursors by repeatedly loading
# {#next} until {#next?} returns `false`. Calls the given block once
# for each result and cursor combination, which are passed as
# parameters.
#
# An Enumerator is returned if no block is given.
#
# This method may make several API calls until all query results are
# retrieved. Be sure to use as narrow a search criteria as possible.
# Please use with caution.
#
# @param [Integer] request_limit The upper limit of API requests to
# make to load all tables. Default is no limit.
# @yield [result, cursor] The block for accessing each query result
# and cursor.
# @yieldparam [Entity] result The query result object.
# @yieldparam [Cursor] cursor The cursor object.
#
# @return [Enumerator]
#
# @example Iterating all results and cursors by passing a block:
# require "google/cloud/datastore"
#
# datastore = Google::Cloud::Datastore.new
#
# query = datastore.query "Task"
# tasks = datastore.run query
# tasks.all_with_cursor do |task, cursor|
# puts "Task #{task.key.id} (#cursor)"
# end
#
# @example Using the enumerator by not passing a block:
# require "google/cloud/datastore"
#
# datastore = Google::Cloud::Datastore.new
#
# query = datastore.query "Task"
# tasks = datastore.run query
# tasks.all_with_cursor.count # number of result/cursor pairs
#
# @example Limit the number of API calls made:
# require "google/cloud/datastore"
#
# datastore = Google::Cloud::Datastore.new
#
# query = datastore.query "Task"
# tasks = datastore.run query
# tasks.all_with_cursor(request_limit: 10) do |task, cursor|
# puts "Task #{task.key.id} (#cursor)"
# end
#
def all_with_cursor request_limit: nil, &block
request_limit = request_limit.to_i if request_limit
unless block_given?
return enum_for :all_with_cursor, request_limit: request_limit
end
results = self
loop do
results.zip(results.cursors).each(&block)
if request_limit
request_limit -= 1
break if request_limit.negative?
end
break unless results.next?
results = results.next
end
end
##
# @private New Dataset::QueryResults from a
# Google::Dataset::V1::RunQueryResponse object.
def self.from_grpc query_res, service, namespace, query
r, c = Array(query_res.batch.entity_results).map do |result|
[Entity.from_grpc(result.entity), Cursor.from_grpc(result.cursor)]
end.transpose
r ||= []
c ||= []
new(r).tap do |qr|
qr.cursors = c
qr.end_cursor = Cursor.from_grpc query_res.batch.end_cursor
qr.more_results = query_res.batch.more_results
qr.service = service
qr.namespace = namespace
qr.query = query_res.query || query
end
end
protected
##
# @private Raise an error unless an active connection to the service
# is available.
def ensure_service!
msg = "Must have active connection to datastore service to get next"
raise msg if @service.nil? || @query.nil?
end
end
end
end
end
end