Add streaming buffer attributes to Table

[refs #1631]

google-cloud-bigquery/acceptance/bigquery/table_test.rb

@@ -85,6 +85,12 @@
     fresh.time_partitioning_type.must_be_nil
     fresh.time_partitioning_expiration.must_be_nil
     #fresh.location.must_equal "US"       TODO why nil? Set in dataset
+
+    # streaming buffer is transient, it seems it may or may not be present?
+    fresh.buffer_bytes.must_be_kind_of Integer if fresh.buffer_bytes
+    fresh.buffer_rows.must_be_kind_of Integer if fresh.buffer_rows
+    fresh.buffer_oldest_at.must_be_kind_of Time if fresh.buffer_oldest_at
+
     fresh.schema.must_be_kind_of Google::Cloud::Bigquery::Schema
     fresh.schema.wont_be :empty?
     [:id, :breed, :name, :dob].each { |k| fresh.headers.must_include k }

google-cloud-bigquery/lib/google/cloud/bigquery/table.rb

@@ -479,6 +479,50 @@ def headers
           schema.headers
         end
 
+        ##
+        # A lower-bound estimate of the number of bytes currently in this
+        # table's streaming buffer, if one is present. This field will be absent
+        # if the table is not being streamed to or if there is no data in the
+        # streaming buffer.
+        #
+        # @!group Attributes
+        #
+        def buffer_bytes
+          ensure_full_data!
+          @gapi.streaming_buffer.estimated_bytes if @gapi.streaming_buffer
+        end
+
+        ##
+        # A lower-bound estimate of the number of rows currently in this
+        # table's streaming buffer, if one is present. This field will be absent
+        # if the table is not being streamed to or if there is no data in the
+        # streaming buffer.
+        #
+        # @!group Attributes
+        #
+        def buffer_rows
+          ensure_full_data!
+          @gapi.streaming_buffer.estimated_rows if @gapi.streaming_buffer
+        end
+
+        ##
+        # The time of the oldest entry currently in this table's streaming
+        # buffer, if one is present. This field will be absent if the table is
+        # not being streamed to or if there is no data in the streaming buffer.
+        #
+        # @!group Attributes
+        #
+        def buffer_oldest_at
+          ensure_full_data!
+          return nil unless @gapi.streaming_buffer
+          oldest_entry_time = @gapi.streaming_buffer.oldest_entry_time
+          begin
+            ::Time.at(Integer(oldest_entry_time) / 1000.0)
+          rescue
+            nil
+          end
+        end
+
         ##
         # Retrieves data from the table.
         #

google-cloud-bigquery/test/google/cloud/bigquery/table_attributes_test.rb

@@ -125,5 +125,7 @@ def self.attr_test attr, val
   attr_test :bytes_count, 1000
   attr_test :rows_count, 100
   attr_test :location, "US"
+  attr_test :buffer_bytes, 2000
+  attr_test :buffer_rows, 200
 
 end

google-cloud-bigquery/test/google/cloud/bigquery/table_test.rb

@@ -80,6 +80,12 @@
     table.headers.must_equal [:name, :age, :score, :active, :avatar, :started_at, :duration, :target_end, :birthday]
   end
 
+  it "knows its streaming buffer attributes" do
+    table.buffer_bytes.must_equal 2000
+    table.buffer_rows.must_equal 200
+    table.buffer_oldest_at.must_be_close_to ::Time.now, 1
+  end
+
   it "can delete itself" do
     mock = Minitest::Mock.new
     mock.expect :delete_table, nil,

google-cloud-bigquery/test/helper.rb

@@ -229,7 +229,12 @@ def random_table_hash dataset, id = nil, name = nil, description = nil, project_
       "expirationTime" => time_millis,
       "lastModifiedTime" => time_millis,
       "type" => "TABLE",
-      "location" => "US"
+      "location" => "US",
+      "streamingBuffer" => {
+        "estimatedBytes" => "2000", # String per google/google-api-ruby-client
+        "estimatedRows" => "200", # String per google/google-api-ruby-client
+        "oldestEntryTime" => time_millis
+      }
     }
   end