Add merge support

sdk/cosmos/azure-cosmos/azure/cosmos/_base.py

@@ -147,6 +147,10 @@ def GetHeaders(  # pylint: disable=too-many-statements,too-many-branches
     headers = dict(default_headers)
     options = options or {}
 
+    # SDK supported capabilities header for partition merge support
+    headers[http_constants.HttpHeaders.SDKSupportedCapabilities] = \
+        http_constants.SDKSupportedCapabilities.PARTITION_MERGE
+
     # Generate a new activity ID for each request client side.
     headers[http_constants.HttpHeaders.ActivityId] = GenerateGuidId()
     if cosmos_client_connection.UseMultipleWriteLocations:

sdk/cosmos/azure-cosmos/azure/cosmos/http_constants.py

@@ -373,6 +373,11 @@ class _ErrorCodes:
     # Linux Error Codes
     LinuxConnectionReset = 131
 
+class SDKSupportedCapabilities:
+    """Constants of SDK supported capabilities.
+    """
+    NONE = '0'
+    PARTITION_MERGE = '1'
 
 class StatusCodes:
     """HTTP status codes returned by the REST operations

sdk/cosmos/azure-cosmos/tests/test_partition_merge.py

@@ -0,0 +1,37 @@
+# The MIT License (MIT)
+# Copyright (c) Microsoft Corporation. All rights reserved.
+
+import unittest
+import pytest
+
+import azure.cosmos.cosmos_client as cosmos_client
+import test_config
+from azure.cosmos import http_constants
+
+def response_hook(raw_response):
+    header = raw_response.http_request.headers
+    assert http_constants.HttpHeaders.SDKSupportedCapabilities in header
+    assert header[http_constants.HttpHeaders.SDKSupportedCapabilities] == \
+           http_constants.SDKSupportedCapabilities.PARTITION_MERGE
+
+@pytest.mark.cosmosQuery
+class TestPartitionMerge(unittest.TestCase):
+    configs = test_config.TestConfig
+    host = configs.host
+    masterKey = configs.masterKey
+    TEST_DATABASE_ID = configs.TEST_DATABASE_ID
+    TEST_CONTAINER_ID = configs.TEST_SINGLE_PARTITION_CONTAINER_ID
+
+    @classmethod
+    def setUpClass(cls):
+        cls.client = cosmos_client.CosmosClient(cls.host, cls.masterKey)
+        cls.database = cls.client.get_database_client(cls.TEST_DATABASE_ID)
+        cls.container = cls.database.get_container_client(cls.TEST_CONTAINER_ID)
+
+    def test_header_enabled_partition_merge(self):
+        # This test only runs read API to verify if the header was set correctly, because all APIs are using the same
+        # base method to set the header(GetHeaders).
+        self.container.read(raw_response_hook=response_hook)
+
+if __name__ == "__main__":
+    unittest.main()