Update README.md

Author: ykoyano

README.md

@@ -20,6 +20,7 @@ in:
     - {name: price, type: long}
     - {name: category_id, type: string}
   max: 2000
+  synchronous_method: true
 out:
   type: stdout
 ```
@@ -41,18 +42,42 @@ in:
 ```
 
 ## Optional Configuration
-This plugin uses the gem [`google-cloud(Google Cloud Client Library for Ruby)`](https://github.com/GoogleCloudPlatform/google-cloud-ruby) and queries data using [the synchronous method](https://github.com/GoogleCloudPlatform/google-cloud-ruby/blob/master/google-cloud-bigquery/lib/google/cloud/bigquery/project.rb#L281).
+This plugin uses the gem [`google-cloud(Google Cloud Client Library for Ruby)`](https://github.com/GoogleCloudPlatform/google-cloud-ruby) and queries data using the synchronous method or the asynchronous  method.
 Therefore some optional configuration items comply with the Google Cloud Client Library.
 
-- [max](https://github.com/GoogleCloudPlatform/google-cloud-ruby/blob/master/google-cloud-bigquery/lib/google/cloud/bigquery/project.rb#L315) :
-  - default value : **null** and null value is interpreted as [no maximum row count](https://github.com/GoogleCloudPlatform/google-cloud-ruby/blob/master/google-cloud-bigquery/lib/google/cloud/bigquery/project.rb#L319) in the Google Cloud Client Library.
-- [cache](https://github.com/GoogleCloudPlatform/google-cloud-ruby/blob/master/google-cloud-bigquery/lib/google/cloud/bigquery/project.rb#L331) :
-  - default value : **null** and null value is interpreted as [true](https://github.com/GoogleCloudPlatform/google-cloud-ruby/blob/master/google-cloud-bigquery/lib/google/cloud/bigquery/project.rb#L333) in the Google Cloud Client Library.
-- [timeout](https://github.com/GoogleCloudPlatform/google-cloud-ruby/blob/master/google-cloud-bigquery/lib/google/cloud/bigquery/project.rb#L321) :
-  - default value : **null** and null value is interpreted as [10000](https://github.com/GoogleCloudPlatform/google-cloud-ruby/blob/master/google-cloud-bigquery/lib/google/cloud/bigquery/project.rb#L315) milliseconds in the Google Cloud Client Library.
-- [dryrun](https://github.com/GoogleCloudPlatform/google-cloud-ruby/blob/master/google-cloud-bigquery/lib/google/cloud/bigquery/project.rb#L327) :
-  - default value : **null** and null value is interpreted as [false](https://github.com/GoogleCloudPlatform/google-cloud-ruby/blob/master/google-cloud-bigquery/lib/google/cloud/bigquery/project.rb#L330) in the Google Cloud Client Library.
-- [standard_sql](https://github.com/GoogleCloudPlatform/google-cloud-ruby/blob/master/google-cloud-bigquery/lib/google/cloud/bigquery/project.rb#L343):
-  - default value : **null** and null value is interpreted as [true](https://github.com/GoogleCloudPlatform/google-cloud-ruby/blob/master/google-cloud-bigquery/lib/google/cloud/bigquery/project.rb#L351) in the Google Cloud Client Library.
-- [legacy_sql](https://github.com/GoogleCloudPlatform/google-cloud-ruby/blob/master/google-cloud-bigquery/lib/google/cloud/bigquery/project.rb#L353):
-  - default value : **null** and null value is interpreted as [false](https://github.com/GoogleCloudPlatform/google-cloud-ruby/blob/master/google-cloud-bigquery/lib/google/cloud/bigquery/project.rb#L361) in the Google Cloud Client Library.
+### optional bigquery parameter 
+
+The detail of follows params is [here](https://github.com/GoogleCloudPlatform/google-cloud-ruby/blob/master/google-cloud-bigquery/lib/google/cloud/bigquery/project.rb).
+
+- max :
+  - default value : **null** and null value is interpreted as no maximum row count in the Google Cloud Client Library. This param is supported only synchronous method.
+- cache :
+  - default value : **null** and null value is interpreted as true in the Google Cloud Client Library. 
+- timeout :
+  - default value : **null** and null value is interpreted as 10000 milliseconds in the Google Cloud Client Library. This param is supported only synchronous method.
+- dryrun :
+  - default value : **null** and null value is interpreted as false in the Google Cloud Client Library. This param is supported only synchronous method.
+- standard_sql :
+  - default value : **null** and null value is interpreted as true in the Google Cloud Client Library.
+- legacy_sql :
+  - default value : **null** and null value is interpreted as false in the Google Cloud Client Library.
+- large_results :
+  - default value : **null** and null value is interpreted as false in the Google Cloud Client Library. This param is supported only asynchronous method.
+- write : 
+  - default value : **null** and null value is interpreted as empty in the Google Cloud Client Library. This param is supported only asynchronous method.
+
+### the bigquery method
+Big query library in Google Cloud Client Library has [two methods](https://github.com/GoogleCloudPlatform/google-cloud-ruby/blob/master/google-cloud-bigquery/lib/google/cloud/bigquery/project.rb) for query.
+
+The default method in this plugin is synchronous_method.
+The logic which how select query method is [here](https://github.com/ykoyano/embulk-input-bigquery/blob/master/lib/embulk/input/bigquery.rb#L41).
+ 
+- synchronous_method:
+   - type : boolean
+   - default value : **null**
+   - This method uses `query` method in the Google Cloud Client Library.
+   - It should be noted that the number of records for `query` method is **limited**. Therefore, if you get many records, you should use `query_job` method with asynchronous_method option.
+- asynchronous_method:
+   - type : boolean
+   - default value : **null**
+   - This method uses `query_job` method in the Google Cloud Client Library.