Class: Google::Cloud::Datastore::Dataset::QueryResults

Inherits:
Array
  • Object
show all
Defined in:
lib/google/cloud/datastore/dataset/query_results.rb

Overview

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.

Examples:

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"

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

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#batch_read_time ⇒ Object (readonly)

Read timestamp this batch was returned from. This applies to the range of results from the query's start_cursor (or the beginning of the query if no cursor was given) to this batch's end_cursor (not the query's end_cursor).

In a single transaction, subsequent query result batches for the same query can have a greater timestamp. Each batch's read timestamp is valid for all preceding batches. This value will not be set for eventually consistent queries in Cloud Datastore.



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# File 'lib/google/cloud/datastore/dataset/query_results.rb', line 86

def batch_read_time
  @batch_read_time
end

#end_cursor ⇒ Google::Cloud::Datastore::Cursor Also known as: cursor

The end_cursor of the QueryResults.

Returns:



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# File 'lib/google/cloud/datastore/dataset/query_results.rb', line 61

def end_cursor
  @end_cursor
end

#more_results ⇒ Object

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


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# File 'lib/google/cloud/datastore/dataset/query_results.rb', line 73

def more_results
  @more_results
end

#read_time ⇒ Object (readonly)

Time at which the entities are being read. This would not be older than 270 seconds.



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# File 'lib/google/cloud/datastore/dataset/query_results.rb', line 91

def read_time
  @read_time
end

Instance Method Details

#all(request_limit: nil) {|result| ... } ⇒ Enumerator

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.

Examples:

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

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

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

Parameters:

  • request_limit (Integer) (defaults to: nil) —

    The upper limit of API requests to make to load all query results. Default is no limit.

Yields:

  • (result) —

    The block for accessing each query result.

Yield Parameters:

  • result (Entity) —

    The query result object.

Returns:

  • (Enumerator) 


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# File 'lib/google/cloud/datastore/dataset/query_results.rb', line 291

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

#all_with_cursor(request_limit: nil) {|result, cursor| ... } ⇒ Enumerator

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.

Examples:

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

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

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

Parameters:

  • request_limit (Integer) (defaults to: nil) —

    The upper limit of API requests to make to load all tables. Default is no limit.

Yields:

  • (result, cursor) —

    The block for accessing each query result and cursor.

Yield Parameters:

  • result (Entity) —

    The query result object.

  • cursor (Cursor) —

    The cursor object.

Returns:

  • (Enumerator) 


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# File 'lib/google/cloud/datastore/dataset/query_results.rb', line 360

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

#cursor_for(result) ⇒ Cursor

Retrieve the Cursor for the provided result.

Examples:

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

Parameters:

  • result (Entity) —

    The entity object to get a cursor for.

Returns:



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# File 'lib/google/cloud/datastore/dataset/query_results.rb', line 205

def cursor_for result
  cursor_index = index result
  return nil if cursor_index.nil?
  cursors[cursor_index]
end

#each_with_cursor {|result, cursor| ... } ⇒ Enumerator

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.

Examples:

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

Yields:

  • (result, cursor) —

    The block for accessing each query result and cursor.

Yield Parameters:

  • result (Entity) —

    The query result object.

  • cursor (Cursor) —

    The cursor object.

Returns:

  • (Enumerator) 


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# File 'lib/google/cloud/datastore/dataset/query_results.rb', line 235

def each_with_cursor
  return enum_for :each_with_cursor unless block_given?
  zip(cursors).each { |r, c| yield [r, c] }
end

#more_after_cursor? ⇒ Boolean

Convenience method for determining if the more_results value is :MORE_RESULTS_AFTER_CURSOR

Returns:

  • (Boolean) 


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# File 'lib/google/cloud/datastore/dataset/query_results.rb', line 118

def more_after_cursor?
  more_results == :MORE_RESULTS_AFTER_CURSOR
end

#more_after_limit? ⇒ Boolean

Convenience method for determining if the more_results value is :MORE_RESULTS_AFTER_LIMIT

Returns:

  • (Boolean) 


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# File 'lib/google/cloud/datastore/dataset/query_results.rb', line 111

def more_after_limit?
  more_results == :MORE_RESULTS_AFTER_LIMIT
end

#next ⇒ QueryResults

Retrieve the next page of results.

Examples:

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

Returns:



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# File 'lib/google/cloud/datastore/dataset/query_results.rb', line 173

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, read_time: read_time
  self.class.from_grpc query_res, service, namespace, query, read_time
end

#next? ⇒ Boolean

Whether there are more results available.

Examples:

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

Returns:

  • (Boolean) 


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# File 'lib/google/cloud/datastore/dataset/query_results.rb', line 152

def next?
  not_finished?
end

#no_more? ⇒ Boolean

Convenience method for determining if the more_results value is :NO_MORE_RESULTS

Returns:

  • (Boolean) 


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# File 'lib/google/cloud/datastore/dataset/query_results.rb', line 125

def no_more?
  more_results == :NO_MORE_RESULTS
end

#not_finished? ⇒ Boolean

Convenience method for determining if the more_results value is :NOT_FINISHED

Returns:

  • (Boolean) 


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# File 'lib/google/cloud/datastore/dataset/query_results.rb', line 104

def not_finished?
  more_results == :NOT_FINISHED
end