Add sample to delete data. (GoogleCloudPlatform#1872)

* Update snippets.py

* Update snippets_test.py

Author: RobinRH

spanner/cloud-client/snippets.py

@@ -93,6 +93,30 @@ def insert_data(instance_id, database_id):
 # [END spanner_insert_data]
 
 
+# [START spanner_delete_data]
+def delete_data(instance_id, database_id):
+    """Deletes sample data from the given database.
+
+    The database, table, and data must already exist and can be created using
+    `create_database` and `insert_data`.
+    """
+    spanner_client = spanner.Client()
+    instance = spanner_client.instance(instance_id)
+    database = instance.database(database_id)
+
+    singers_to_delete = spanner.KeySet(
+        keys=[[1], [2], [3], [4], [5]])
+    albums_to_delete = spanner.KeySet(
+        keys=[[1, 1], [1, 2], [2, 1], [2, 2], [2, 3]])
+
+    with database.batch() as batch:
+        batch.delete('Albums', albums_to_delete)
+        batch.delete('Singers', singers_to_delete)
+
+    print('Deleted data.')
+# [END spanner_delete_data]
+
+
 # [START spanner_query_data]
 def query_data(instance_id, database_id):
     """Queries sample data from the database using SQL."""
@@ -1027,6 +1051,7 @@ def delete_data_with_partitioned_dml(instance_id, database_id):
 
     subparsers = parser.add_subparsers(dest='command')
     subparsers.add_parser('create_database', help=create_database.__doc__)
+    subparsers.add_parser('delete_data', help=delete_data.__doc__)
     subparsers.add_parser('insert_data', help=insert_data.__doc__)
     subparsers.add_parser('query_data', help=query_data.__doc__)
     subparsers.add_parser('read_data', help=read_data.__doc__)
@@ -1100,6 +1125,8 @@ def delete_data_with_partitioned_dml(instance_id, database_id):
         create_database(args.instance_id, args.database_id)
     elif args.command == 'insert_data':
         insert_data(args.instance_id, args.database_id)
+    elif args.command == 'delete_data':
+        delete_data(args.instance_id, args.database_id)
     elif args.command == 'query_data':
         query_data(args.instance_id, args.database_id)
     elif args.command == 'read_data':

spanner/cloud-client/snippets_test.py

@@ -59,6 +59,13 @@ def test_insert_data(capsys):
     assert 'Inserted data' in out
 
 
+def test_delete_data(capsys):
+    snippets.delete_data(INSTANCE_ID, DATABASE_ID)
+    snippets.insert_data(INSTANCE_ID, DATABASE_ID)
+    out, _ = capsys.readouterr()
+    assert 'Deleted data' in out
+
+
 def test_query_data(capsys):
     snippets.query_data(INSTANCE_ID, DATABASE_ID)
     out, _ = capsys.readouterr()