diff --git a/pgsync/sync.py b/pgsync/sync.py
index 9f563c8..e6f8ca2 100644
--- a/pgsync/sync.py
+++ b/pgsync/sync.py
@@ -983,6 +983,18 @@ def sync(
 
                 row[META] = Transform.get_primary_keys(keys)
 
+                if node.is_root:
+                    primary_key_values: t.List[str] = list(
+                        map(str, primary_keys)
+                    )
+                    primary_key_names: t.List[str] = [
+                        primary_key.name for primary_key in node.primary_keys
+                    ]
+                    # TODO: add support for composite pkeys
+                    row[META][node.table] = {
+                        primary_key_names[0]: [primary_key_values[0]],
+                    }
+
                 if self.verbose:
                     print(f"{(i+1)})")
                     print(f"pkeys: {primary_keys}")
diff --git a/requirements/base.txt b/requirements/base.txt
index 762414c..9540fc5 100644
--- a/requirements/base.txt
+++ b/requirements/base.txt
@@ -6,9 +6,9 @@
 #
 async-timeout==4.0.3
     # via redis
-boto3==1.34.159
+boto3==1.35.5
     # via -r requirements/base.in
-botocore==1.34.159
+botocore==1.35.5
     # via
     #   boto3
     #   s3transfer
@@ -27,7 +27,7 @@ elasticsearch==8.15.0
     # via
     #   -r requirements/base.in
     #   elasticsearch-dsl
-elasticsearch-dsl==8.15.0
+elasticsearch-dsl==8.15.1
     # via -r requirements/base.in
 environs==11.0.0
     # via -r requirements/base.in
@@ -35,17 +35,17 @@ events==0.5
     # via opensearch-py
 greenlet==3.0.3
     # via sqlalchemy
-idna==3.7
+idna==3.8
     # via requests
 jmespath==1.0.1
     # via
     #   boto3
     #   botocore
-marshmallow==3.21.3
+marshmallow==3.22.0
     # via environs
 opensearch-dsl==2.1.0
     # via -r requirements/base.in
-opensearch-py==2.6.0
+opensearch-py==2.7.1
     # via opensearch-dsl
 packaging==24.1
     # via marshmallow
@@ -74,7 +74,6 @@ s3transfer==0.10.2
 six==1.16.0
     # via
     #   opensearch-dsl
-    #   opensearch-py
     #   python-dateutil
 sqlalchemy==2.0.32
     # via -r requirements/base.in
diff --git a/requirements/dev.txt b/requirements/dev.txt
index f845cc7..bc56290 100644
--- a/requirements/dev.txt
+++ b/requirements/dev.txt
@@ -8,9 +8,9 @@ async-timeout==4.0.3
     # via redis
 black==24.8.0
     # via -r requirements/dev.in
-boto3==1.34.159
+boto3==1.35.5
     # via -r requirements/base.in
-botocore==1.34.159
+botocore==1.35.5
     # via
     #   boto3
     #   s3transfer
@@ -39,7 +39,7 @@ elasticsearch==8.15.0
     # via
     #   -r requirements/base.in
     #   elasticsearch-dsl
-elasticsearch-dsl==8.15.0
+elasticsearch-dsl==8.15.1
     # via -r requirements/base.in
 environs==11.0.0
     # via -r requirements/base.in
@@ -47,7 +47,7 @@ events==0.5
     # via opensearch-py
 exceptiongroup==1.2.2
     # via pytest
-faker==27.0.0
+faker==28.0.0
     # via -r requirements/dev.in
 filelock==3.15.4
     # via virtualenv
@@ -59,7 +59,7 @@ greenlet==3.0.3
     # via sqlalchemy
 identify==2.6.0
     # via pre-commit
-idna==3.7
+idna==3.8
     # via requests
 iniconfig==2.0.0
     # via pytest
@@ -69,7 +69,7 @@ jmespath==1.0.1
     # via
     #   boto3
     #   botocore
-marshmallow==3.21.3
+marshmallow==3.22.0
     # via environs
 mccabe==0.7.0
     # via flake8
@@ -81,7 +81,7 @@ nodeenv==1.9.1
     # via pre-commit
 opensearch-dsl==2.1.0
     # via -r requirements/base.in
-opensearch-py==2.6.0
+opensearch-py==2.7.1
     # via opensearch-dsl
 packaging==24.1
     # via
@@ -140,7 +140,6 @@ s3transfer==0.10.2
 six==1.16.0
     # via
     #   opensearch-dsl
-    #   opensearch-py
     #   python-dateutil
 sqlalchemy==2.0.32
     # via -r requirements/base.in
diff --git a/tests/test_sync_nested_children.py b/tests/test_sync_nested_children.py
index 6b73336..f72a0b5 100644
--- a/tests/test_sync_nested_children.py
+++ b/tests/test_sync_nested_children.py
@@ -391,6 +391,7 @@ def test_sync(self, sync, nodes, data):
                 "_index": "testdb",
                 "_source": {
                     "_meta": {
+                        "book": {"isbn": ["abc"]},
                         "author": {"id": [1, 4]},
                         "book_author": {"id": [1, 4]},
                         "book_language": {"id": [1, 4, 7, 9]},
@@ -449,6 +450,7 @@ def test_sync(self, sync, nodes, data):
                 "_index": "testdb",
                 "_source": {
                     "_meta": {
+                        "book": {"isbn": ["def"]},
                         "author": {"id": [1, 2]},
                         "book_author": {"id": [2, 5]},
                         "book_language": {"id": [2, 5, 8]},
@@ -506,6 +508,7 @@ def test_sync(self, sync, nodes, data):
                 "_index": "testdb",
                 "_source": {
                     "_meta": {
+                        "book": {"isbn": ["ghi"]},
                         "author": {"id": [2, 3]},
                         "book_author": {"id": [3, 6]},
                         "book_language": {"id": [3, 6]},
@@ -708,6 +711,7 @@ def test_insert_root(
                 "_index": "testdb",
                 "_source": {
                     "_meta": {
+                        "book": {"isbn": ["jkl"]},
                         "author": {"id": [5]},
                         "book_author": {"id": [7]},
                         "book_language": {"id": [10, 11]},
@@ -753,6 +757,7 @@ def test_insert_root(
                 "_index": "testdb",
                 "_source": {
                     "_meta": {
+                        "book": {"isbn": ["mno"]},
                         "author": {"id": [5]},
                         "book_author": {"id": [8]},
                         "book_language": {"id": [12, 13]},
@@ -834,6 +839,7 @@ def test_update_root(self, data, nodes, book_cls):
                 "_index": "testdb",
                 "_source": {
                     "_meta": {
+                        "book": {"isbn": ["abc"]},
                         "author": {"id": [1, 4]},
                         "book_author": {"id": [1, 4]},
                         "book_language": {"id": [1, 4, 7, 9]},
@@ -1001,6 +1007,7 @@ def poll_db():
         expected = [
             {
                 "_meta": {
+                    "book": {"isbn": ["def"]},
                     "author": {"id": [1, 2]},
                     "book_author": {"id": [2, 5]},
                     "book_language": {"id": [2, 5, 8]},
@@ -1054,6 +1061,7 @@ def poll_db():
             },
             {
                 "_meta": {
+                    "book": {"isbn": ["ghi"]},
                     "author": {"id": [2, 3]},
                     "book_author": {"id": [3, 6]},
                     "book_language": {"id": [3, 6]},
@@ -1174,7 +1182,7 @@ def test_insert_through_child_op2(
                     "isbn": "abc",
                     "group": None,
                     "title": "The Tiger Club",
-                    "_meta": {},
+                    "_meta": {"book": {"isbn": ["abc"]}},
                 },
             },
             {
@@ -1184,7 +1192,7 @@ def test_insert_through_child_op2(
                     "isbn": "def",
                     "group": None,
                     "title": "The Lion Club",
-                    "_meta": {},
+                    "_meta": {"book": {"isbn": ["def"]}},
                 },
             },
             {
@@ -1194,7 +1202,7 @@ def test_insert_through_child_op2(
                     "isbn": "ghi",
                     "group": None,
                     "title": "The Rabbit Club",
-                    "_meta": {},
+                    "_meta": {"book": {"isbn": ["ghi"]}},
                 },
             },
         ]
@@ -1249,6 +1257,7 @@ def poll_db():
                     ],
                     "title": "The Tiger Club",
                     "_meta": {
+                        "book": {"isbn": ["abc"]},
                         "group": {"id": [1, 2]},
                         "book_group": {"id": [1, 2]},
                     },
@@ -1261,7 +1270,7 @@ def poll_db():
                     "isbn": "def",
                     "group": None,
                     "title": "The Lion Club",
-                    "_meta": {},
+                    "_meta": {"book": {"isbn": ["def"]}},
                 },
             },
             {
@@ -1271,7 +1280,7 @@ def poll_db():
                     "isbn": "ghi",
                     "group": None,
                     "title": "The Rabbit Club",
-                    "_meta": {},
+                    "_meta": {"book": {"isbn": ["ghi"]}},
                 },
             },
         ]
@@ -1346,6 +1355,7 @@ def test_insert_through_child_op(
         expected = [
             {
                 "_meta": {
+                    "book": {"isbn": ["abc"]},
                     "author": {"id": [1, 4, 5]},
                     "book_author": {"id": [1, 4, 7]},
                     "book_language": {"id": [1, 4, 7, 9]},
@@ -1413,6 +1423,7 @@ def test_insert_through_child_op(
             },
             {
                 "_meta": {
+                    "book": {"isbn": ["def"]},
                     "author": {"id": [1, 2]},
                     "book_author": {"id": [2, 5]},
                     "book_language": {"id": [2, 5, 8]},
@@ -1466,6 +1477,7 @@ def test_insert_through_child_op(
             },
             {
                 "_meta": {
+                    "book": {"isbn": ["ghi"]},
                     "author": {"id": [2, 3]},
                     "book_author": {"id": [3, 6]},
                     "book_language": {"id": [3, 6]},
@@ -1602,6 +1614,7 @@ def test_update_through_child_op(
         expected = [
             {
                 "_meta": {
+                    "book": {"isbn": ["abc"]},
                     "author": {"id": [4, 5]},
                     "book_author": {"id": [1, 4]},
                     "book_language": {"id": [1, 4, 7, 9]},
@@ -1656,6 +1669,7 @@ def test_update_through_child_op(
             },
             {
                 "_meta": {
+                    "book": {"isbn": ["def"]},
                     "author": {"id": [1, 2]},
                     "book_author": {"id": [2, 5]},
                     "book_language": {"id": [2, 5, 8]},
@@ -1709,6 +1723,7 @@ def test_update_through_child_op(
             },
             {
                 "_meta": {
+                    "book": {"isbn": ["ghi"]},
                     "author": {"id": [2, 3]},
                     "book_author": {"id": [3, 6]},
                     "book_language": {"id": [3, 6]},
@@ -1818,6 +1833,7 @@ def test_delete_through_child_op(self, sync, data, nodes, book_author_cls):
         expected = [
             {
                 "_meta": {
+                    "book": {"isbn": ["abc"]},
                     "book_language": {"id": [1, 4, 7, 9]},
                     "book_subject": {"id": [1, 4, 6]},
                     "language": {"id": [1, 2, 3, 4]},
@@ -1840,6 +1856,7 @@ def test_delete_through_child_op(self, sync, data, nodes, book_author_cls):
             },
             {
                 "_meta": {
+                    "book": {"isbn": ["def"]},
                     "author": {"id": [1, 2]},
                     "book_author": {"id": [2, 5]},
                     "book_language": {"id": [2, 5, 8]},
@@ -1893,6 +1910,7 @@ def test_delete_through_child_op(self, sync, data, nodes, book_author_cls):
             },
             {
                 "_meta": {
+                    "book": {"isbn": ["ghi"]},
                     "author": {"id": [2, 3]},
                     "book_author": {"id": [3, 6]},
                     "book_language": {"id": [3, 6]},
diff --git a/tests/test_sync_root.py b/tests/test_sync_root.py
index 23b2719..da901f0 100644
--- a/tests/test_sync_root.py
+++ b/tests/test_sync_root.py
@@ -100,7 +100,9 @@ def test_sync2(self, sync, data):
                 "_id": "abc",
                 "_index": "testdb",
                 "_source": {
-                    "_meta": {},
+                    "_meta": {
+                        "book": {"isbn": ["abc"]},
+                    },
                     "description": "Tigers are fierce creatures",
                     "isbn": "abc",
                     "title": "The Tiger Club",
@@ -110,7 +112,9 @@ def test_sync2(self, sync, data):
                 "_id": "def",
                 "_index": "testdb",
                 "_source": {
-                    "_meta": {},
+                    "_meta": {
+                        "book": {"isbn": ["def"]},
+                    },
                     "description": "Lion and the mouse",
                     "isbn": "def",
                     "title": "The Lion Club",
@@ -120,7 +124,7 @@ def test_sync2(self, sync, data):
                 "_id": "ghi",
                 "_index": "testdb",
                 "_source": {
-                    "_meta": {},
+                    "_meta": {"book": {"isbn": ["ghi"]}},
                     "description": "Rabbits on the run",
                     "isbn": "ghi",
                     "title": "The Rabbit Club",
@@ -151,7 +155,9 @@ def test_transform(self, sync, data):
                 "_id": "abc",
                 "_index": "testdb",
                 "_source": {
-                    "_meta": {},
+                    "_meta": {
+                        "book": {"isbn": ["abc"]},
+                    },
                     "description": "Tigers are fierce creatures",
                     "book_isbn": "abc",
                     "book_title": "The Tiger Club",
@@ -161,7 +167,9 @@ def test_transform(self, sync, data):
                 "_id": "def",
                 "_index": "testdb",
                 "_source": {
-                    "_meta": {},
+                    "_meta": {
+                        "book": {"isbn": ["def"]},
+                    },
                     "description": "Lion and the mouse",
                     "book_isbn": "def",
                     "book_title": "The Lion Club",
@@ -171,7 +179,7 @@ def test_transform(self, sync, data):
                 "_id": "ghi",
                 "_index": "testdb",
                 "_source": {
-                    "_meta": {},
+                    "_meta": {"book": {"isbn": ["ghi"]}},
                     "description": "Rabbits on the run",
                     "book_isbn": "ghi",
                     "book_title": "The Rabbit Club",
@@ -338,19 +346,19 @@ def test_doc_includes_nulls(self, sync, data):
 
         assert sources == {
             "abc": {
-                "_meta": {},
+                "_meta": {"book": {"isbn": ["abc"]}},
                 "copyright": None,
                 "description": "Tigers are fierce creatures",
                 "isbn": "abc",
             },
             "def": {
-                "_meta": {},
+                "_meta": {"book": {"isbn": ["def"]}},
                 "copyright": None,
                 "description": "Lion and the mouse",
                 "isbn": "def",
             },
             "ghi": {
-                "_meta": {},
+                "_meta": {"book": {"isbn": ["ghi"]}},
                 "copyright": None,
                 "description": "Rabbits on the run",
                 "isbn": "ghi",
@@ -366,9 +374,9 @@ def test_meta_keys(self, sync, data):
         docs = [doc for doc in sync.sync()]
         sources = {doc["_id"]: doc["_source"] for doc in docs}
 
-        assert sources["abc"]["_meta"] == {}
-        assert sources["def"]["_meta"] == {}
-        assert sources["ghi"]["_meta"] == {}
+        assert sources["abc"]["_meta"] == {"book": {"isbn": ["abc"]}}
+        assert sources["def"]["_meta"] == {"book": {"isbn": ["def"]}}
+        assert sources["ghi"]["_meta"] == {"book": {"isbn": ["ghi"]}}
         assert_resync_empty(sync, nodes)
 
     def test_node_include_table(self, sync, data):
@@ -407,9 +415,21 @@ def test_update_primary_key_non_concurrent(self, data, book_cls):
         docs = search(sync.search_client, "testdb")
 
         assert docs == [
-            {"_meta": {}, "isbn": "abc", "title": "The Tiger Club"},
-            {"_meta": {}, "isbn": "def", "title": "The Lion Club"},
-            {"_meta": {}, "isbn": "ghi", "title": "The Rabbit Club"},
+            {
+                "_meta": {"book": {"isbn": ["abc"]}},
+                "isbn": "abc",
+                "title": "The Tiger Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["def"]}},
+                "isbn": "def",
+                "title": "The Lion Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["ghi"]}},
+                "isbn": "ghi",
+                "title": "The Rabbit Club",
+            },
         ]
 
         session = sync.session
@@ -426,10 +446,26 @@ def test_update_primary_key_non_concurrent(self, data, book_cls):
         docs = search(sync.search_client, "testdb")
 
         assert docs == [
-            {"_meta": {}, "isbn": "abc", "title": "The Tiger Club"},
-            {"_meta": {}, "isbn": "cba", "title": "The Tiger Club"},
-            {"_meta": {}, "isbn": "def", "title": "The Lion Club"},
-            {"_meta": {}, "isbn": "ghi", "title": "The Rabbit Club"},
+            {
+                "_meta": {"book": {"isbn": ["abc"]}},
+                "isbn": "abc",
+                "title": "The Tiger Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["cba"]}},
+                "isbn": "cba",
+                "title": "The Tiger Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["def"]}},
+                "isbn": "def",
+                "title": "The Lion Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["ghi"]}},
+                "isbn": "ghi",
+                "title": "The Rabbit Club",
+            },
         ]
         assert_resync_empty(sync, doc.get("node", {}))
         sync.search_client.close()
@@ -450,9 +486,21 @@ def test_update_primary_key_concurrent(self, data, book_cls):
         docs = search(sync.search_client, "testdb")
 
         assert docs == [
-            {"_meta": {}, "isbn": "abc", "title": "The Tiger Club"},
-            {"_meta": {}, "isbn": "def", "title": "The Lion Club"},
-            {"_meta": {}, "isbn": "ghi", "title": "The Rabbit Club"},
+            {
+                "_meta": {"book": {"isbn": ["abc"]}},
+                "isbn": "abc",
+                "title": "The Tiger Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["def"]}},
+                "isbn": "def",
+                "title": "The Lion Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["ghi"]}},
+                "isbn": "ghi",
+                "title": "The Rabbit Club",
+            },
         ]
 
         session = sync.session
@@ -495,9 +543,21 @@ def poll_db():
         assert "abc" not in [doc["isbn"] for doc in docs]
 
         assert docs == [
-            {"_meta": {}, "isbn": "cba", "title": "The Tiger Club"},
-            {"_meta": {}, "isbn": "def", "title": "The Lion Club"},
-            {"_meta": {}, "isbn": "ghi", "title": "The Rabbit Club"},
+            {
+                "_meta": {"book": {"isbn": ["cba"]}},
+                "isbn": "cba",
+                "title": "The Tiger Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["def"]}},
+                "isbn": "def",
+                "title": "The Lion Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["ghi"]}},
+                "isbn": "ghi",
+                "title": "The Rabbit Club",
+            },
         ]
         assert_resync_empty(sync, doc.get("node", {}))
         sync.search_client.close()
@@ -518,9 +578,21 @@ def test_insert_non_concurrent(self, data, book_cls):
         docs = search(sync.search_client, "testdb")
 
         assert docs == [
-            {"_meta": {}, "isbn": "abc", "title": "The Tiger Club"},
-            {"_meta": {}, "isbn": "def", "title": "The Lion Club"},
-            {"_meta": {}, "isbn": "ghi", "title": "The Rabbit Club"},
+            {
+                "_meta": {"book": {"isbn": ["abc"]}},
+                "isbn": "abc",
+                "title": "The Tiger Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["def"]}},
+                "isbn": "def",
+                "title": "The Lion Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["ghi"]}},
+                "isbn": "ghi",
+                "title": "The Rabbit Club",
+            },
         ]
         with subtransactions(session):
             session.execute(
@@ -535,10 +607,26 @@ def test_insert_non_concurrent(self, data, book_cls):
         docs = search(sync.search_client, "testdb")
 
         assert docs == [
-            {"_meta": {}, "isbn": "abc", "title": "The Tiger Club"},
-            {"_meta": {}, "isbn": "def", "title": "The Lion Club"},
-            {"_meta": {}, "isbn": "ghi", "title": "The Rabbit Club"},
-            {"_meta": {}, "isbn": "xyz", "title": "Encyclopedia"},
+            {
+                "_meta": {"book": {"isbn": ["abc"]}},
+                "isbn": "abc",
+                "title": "The Tiger Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["def"]}},
+                "isbn": "def",
+                "title": "The Lion Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["ghi"]}},
+                "isbn": "ghi",
+                "title": "The Rabbit Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["xyz"]}},
+                "isbn": "xyz",
+                "title": "Encyclopedia",
+            },
         ]
         assert_resync_empty(sync, doc.get("node", {}))
         sync.search_client.close()
@@ -559,9 +647,21 @@ def test_update_non_concurrent(self, data, book_cls):
         docs = search(sync.search_client, "testdb")
 
         assert docs == [
-            {"_meta": {}, "isbn": "abc", "title": "The Tiger Club"},
-            {"_meta": {}, "isbn": "def", "title": "The Lion Club"},
-            {"_meta": {}, "isbn": "ghi", "title": "The Rabbit Club"},
+            {
+                "_meta": {"book": {"isbn": ["abc"]}},
+                "isbn": "abc",
+                "title": "The Tiger Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["def"]}},
+                "isbn": "def",
+                "title": "The Lion Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["ghi"]}},
+                "isbn": "ghi",
+                "title": "The Rabbit Club",
+            },
         ]
 
         with subtransactions(session):
@@ -577,9 +677,21 @@ def test_update_non_concurrent(self, data, book_cls):
         docs = search(sync.search_client, "testdb")
 
         assert docs == [
-            {"_meta": {}, "isbn": "abc", "title": "Tiger Club"},
-            {"_meta": {}, "isbn": "def", "title": "The Lion Club"},
-            {"_meta": {}, "isbn": "ghi", "title": "The Rabbit Club"},
+            {
+                "_meta": {"book": {"isbn": ["abc"]}},
+                "isbn": "abc",
+                "title": "Tiger Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["def"]}},
+                "isbn": "def",
+                "title": "The Lion Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["ghi"]}},
+                "isbn": "ghi",
+                "title": "The Rabbit Club",
+            },
         ]
         assert_resync_empty(sync, doc.get("node", {}))
         sync.search_client.close()
@@ -600,9 +712,21 @@ def test_update_concurrent(self, data, book_cls):
         docs = search(sync.search_client, "testdb")
 
         assert docs == [
-            {"_meta": {}, "isbn": "abc", "title": "The Tiger Club"},
-            {"_meta": {}, "isbn": "def", "title": "The Lion Club"},
-            {"_meta": {}, "isbn": "ghi", "title": "The Rabbit Club"},
+            {
+                "_meta": {"book": {"isbn": ["abc"]}},
+                "isbn": "abc",
+                "title": "The Tiger Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["def"]}},
+                "isbn": "def",
+                "title": "The Lion Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["ghi"]}},
+                "isbn": "ghi",
+                "title": "The Rabbit Club",
+            },
         ]
 
         def pull():
@@ -639,9 +763,21 @@ def poll_db():
         docs = search(sync.search_client, "testdb")
 
         assert docs == [
-            {"_meta": {}, "isbn": "abc", "title": "Tiger Club"},
-            {"_meta": {}, "isbn": "def", "title": "The Lion Club"},
-            {"_meta": {}, "isbn": "ghi", "title": "The Rabbit Club"},
+            {
+                "_meta": {"book": {"isbn": ["abc"]}},
+                "isbn": "abc",
+                "title": "Tiger Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["def"]}},
+                "isbn": "def",
+                "title": "The Lion Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["ghi"]}},
+                "isbn": "ghi",
+                "title": "The Rabbit Club",
+            },
         ]
         assert_resync_empty(sync, doc.get("node", {}))
         sync.search_client.close()
@@ -660,9 +796,21 @@ def test_delete_concurrent(self, data, book_cls):
         docs = search(sync.search_client, "testdb")
 
         assert docs == [
-            {"_meta": {}, "isbn": "abc", "title": "The Tiger Club"},
-            {"_meta": {}, "isbn": "def", "title": "The Lion Club"},
-            {"_meta": {}, "isbn": "ghi", "title": "The Rabbit Club"},
+            {
+                "_meta": {"book": {"isbn": ["abc"]}},
+                "isbn": "abc",
+                "title": "The Tiger Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["def"]}},
+                "isbn": "def",
+                "title": "The Lion Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["ghi"]}},
+                "isbn": "ghi",
+                "title": "The Rabbit Club",
+            },
         ]
 
         def pull():
@@ -699,8 +847,16 @@ def poll_db():
         docs = search(sync.search_client, "testdb")
 
         assert docs == [
-            {"_meta": {}, "isbn": "def", "title": "The Lion Club"},
-            {"_meta": {}, "isbn": "ghi", "title": "The Rabbit Club"},
+            {
+                "_meta": {"book": {"isbn": ["def"]}},
+                "isbn": "def",
+                "title": "The Lion Club",
+            },
+            {
+                "_meta": {"book": {"isbn": ["ghi"]}},
+                "isbn": "ghi",
+                "title": "The Rabbit Club",
+            },
         ]
         assert_resync_empty(sync, doc.get("node", {}))
         sync.search_client.close()
diff --git a/tests/test_sync_single_child_fk_on_child.py b/tests/test_sync_single_child_fk_on_child.py
index 9cb721b..fe5d9fb 100644
--- a/tests/test_sync_single_child_fk_on_child.py
+++ b/tests/test_sync_single_child_fk_on_child.py
@@ -116,7 +116,7 @@ def test_relationship_object_one_to_one(self, sync, data):
         docs = [sort_list(doc) for doc in sync.sync()]
         assert docs[0]["_id"] == "abc"
         assert docs[0]["_source"] == {
-            "_meta": {"rating": {"id": [1]}},
+            "_meta": {"book": {"isbn": ["abc"]}, "rating": {"id": [1]}},
             "description": "Tigers are fierce creatures",
             "isbn": "abc",
             "rating": {"id": 1, "value": 1.1},
@@ -125,7 +125,7 @@ def test_relationship_object_one_to_one(self, sync, data):
 
         assert docs[1]["_id"] == "def"
         assert docs[1]["_source"] == {
-            "_meta": {"rating": {"id": [2]}},
+            "_meta": {"book": {"isbn": ["def"]}, "rating": {"id": [2]}},
             "description": "Lion and the mouse",
             "isbn": "def",
             "rating": {"id": 2, "value": 2.2},
@@ -134,7 +134,7 @@ def test_relationship_object_one_to_one(self, sync, data):
 
         assert docs[2]["_id"] == "ghi"
         assert docs[2]["_source"] == {
-            "_meta": {"rating": {"id": [3]}},
+            "_meta": {"book": {"isbn": ["ghi"]}, "rating": {"id": [3]}},
             "description": "Rabbits on the run",
             "isbn": "ghi",
             "rating": {"id": 3, "value": 3.3},
@@ -163,7 +163,7 @@ def test_relationship_object_one_to_many(self, sync, data):
 
         assert docs[0]["_id"] == "abc"
         assert docs[0]["_source"] == {
-            "_meta": {"rating": {"id": [1]}},
+            "_meta": {"book": {"isbn": ["abc"]}, "rating": {"id": [1]}},
             "description": "Tigers are fierce creatures",
             "isbn": "abc",
             "rating": [{"id": 1, "value": 1.1}],
@@ -172,7 +172,7 @@ def test_relationship_object_one_to_many(self, sync, data):
 
         assert docs[1]["_id"] == "def"
         assert docs[1]["_source"] == {
-            "_meta": {"rating": {"id": [2]}},
+            "_meta": {"book": {"isbn": ["def"]}, "rating": {"id": [2]}},
             "description": "Lion and the mouse",
             "isbn": "def",
             "rating": [{"id": 2, "value": 2.2}],
@@ -181,7 +181,7 @@ def test_relationship_object_one_to_many(self, sync, data):
 
         assert docs[2]["_id"] == "ghi"
         assert docs[2]["_source"] == {
-            "_meta": {"rating": {"id": [3]}},
+            "_meta": {"book": {"isbn": ["ghi"]}, "rating": {"id": [3]}},
             "description": "Rabbits on the run",
             "isbn": "ghi",
             "rating": [{"id": 3, "value": 3.3}],
@@ -208,7 +208,7 @@ def test_relationship_scalar_one_to_one(self, sync, data):
         docs = [sort_list(doc) for doc in sync.sync()]
         assert docs[0]["_id"] == "abc"
         assert docs[0]["_source"] == {
-            "_meta": {"rating": {"id": [1]}},
+            "_meta": {"book": {"isbn": ["abc"]}, "rating": {"id": [1]}},
             "description": "Tigers are fierce creatures",
             "isbn": "abc",
             "rating": 1.1,
@@ -217,7 +217,7 @@ def test_relationship_scalar_one_to_one(self, sync, data):
 
         assert docs[1]["_id"] == "def"
         assert docs[1]["_source"] == {
-            "_meta": {"rating": {"id": [2]}},
+            "_meta": {"book": {"isbn": ["def"]}, "rating": {"id": [2]}},
             "description": "Lion and the mouse",
             "isbn": "def",
             "rating": 2.2,
@@ -226,7 +226,7 @@ def test_relationship_scalar_one_to_one(self, sync, data):
 
         assert docs[2]["_id"] == "ghi"
         assert docs[2]["_source"] == {
-            "_meta": {"rating": {"id": [3]}},
+            "_meta": {"book": {"isbn": ["ghi"]}, "rating": {"id": [3]}},
             "description": "Rabbits on the run",
             "isbn": "ghi",
             "rating": 3.3,
@@ -254,7 +254,7 @@ def test_relationship_scalar_one_to_many(self, sync, data):
         docs = sorted(docs, key=lambda k: k["_id"])
         assert docs[0]["_id"] == "abc"
         assert docs[0]["_source"] == {
-            "_meta": {"rating": {"id": [1]}},
+            "_meta": {"book": {"isbn": ["abc"]}, "rating": {"id": [1]}},
             "description": "Tigers are fierce creatures",
             "isbn": "abc",
             "rating": [1.1],
@@ -263,7 +263,7 @@ def test_relationship_scalar_one_to_many(self, sync, data):
 
         assert docs[1]["_id"] == "def"
         assert docs[1]["_source"] == {
-            "_meta": {"rating": {"id": [2]}},
+            "_meta": {"book": {"isbn": ["def"]}, "rating": {"id": [2]}},
             "description": "Lion and the mouse",
             "isbn": "def",
             "rating": [2.2],
@@ -272,7 +272,7 @@ def test_relationship_scalar_one_to_many(self, sync, data):
 
         assert docs[2]["_id"] == "ghi"
         assert docs[2]["_source"] == {
-            "_meta": {"rating": {"id": [3]}},
+            "_meta": {"book": {"isbn": ["ghi"]}, "rating": {"id": [3]}},
             "description": "Rabbits on the run",
             "isbn": "ghi",
             "rating": [3.3],
@@ -300,7 +300,7 @@ def test_label(self, sync, data):
         docs = [sort_list(doc) for doc in sync.sync()]
         assert docs[0]["_id"] == "abc"
         assert docs[0]["_source"] == {
-            "_meta": {"rating": {"id": [1]}},
+            "_meta": {"book": {"isbn": ["abc"]}, "rating": {"id": [1]}},
             "description": "Tigers are fierce creatures",
             "isbn": "abc",
             "rating_x": 1.1,
@@ -309,7 +309,7 @@ def test_label(self, sync, data):
 
         assert docs[1]["_id"] == "def"
         assert docs[1]["_source"] == {
-            "_meta": {"rating": {"id": [2]}},
+            "_meta": {"book": {"isbn": ["def"]}, "rating": {"id": [2]}},
             "description": "Lion and the mouse",
             "isbn": "def",
             "rating_x": 2.2,
@@ -318,7 +318,7 @@ def test_label(self, sync, data):
 
         assert docs[2]["_id"] == "ghi"
         assert docs[2]["_source"] == {
-            "_meta": {"rating": {"id": [3]}},
+            "_meta": {"book": {"isbn": ["ghi"]}, "rating": {"id": [3]}},
             "description": "Rabbits on the run",
             "isbn": "ghi",
             "rating_x": 3.3,
@@ -347,7 +347,7 @@ def test_null_label(self, sync, data):
         docs = [sort_list(doc) for doc in sync.sync()]
         assert docs[0]["_id"] == "abc"
         assert docs[0]["_source"] == {
-            "_meta": {"rating": {"id": [1]}},
+            "_meta": {"book": {"isbn": ["abc"]}, "rating": {"id": [1]}},
             "description": "Tigers are fierce creatures",
             "isbn": "abc",
             "rating": 1.1,
@@ -382,7 +382,7 @@ def test_transform(self, sync, data):
         assert docs[0]["_id"] == "abc"
 
         assert docs[0]["_source"] == {
-            "_meta": {"rating": {"id": [1]}},
+            "_meta": {"book": {"isbn": ["abc"]}, "rating": {"id": [1]}},
             "book_isbn": "abc",
             "book_title": "The Tiger Club",
             "description": "Tigers are fierce creatures",
@@ -390,7 +390,7 @@ def test_transform(self, sync, data):
         }
         assert docs[1]["_id"] == "def"
         assert docs[1]["_source"] == {
-            "_meta": {"rating": {"id": [2]}},
+            "_meta": {"book": {"isbn": ["def"]}, "rating": {"id": [2]}},
             "book_isbn": "def",
             "book_title": "The Lion Club",
             "description": "Lion and the mouse",
@@ -399,7 +399,7 @@ def test_transform(self, sync, data):
 
         assert docs[2]["_id"] == "ghi"
         assert docs[2]["_source"] == {
-            "_meta": {"rating": {"id": [3]}},
+            "_meta": {"book": {"isbn": ["ghi"]}, "rating": {"id": [3]}},
             "book_isbn": "ghi",
             "book_title": "The Rabbit Club",
             "description": "Rabbits on the run",
@@ -452,7 +452,7 @@ def test_schema_with_no_column_specified(self, sync, data):
         sync.tree = Tree(sync.models, nodes)
         docs = [sort_list(doc) for doc in sync.sync()]
         assert docs[2]["_source"] == {
-            "_meta": {"rating": {"id": [3]}},
+            "_meta": {"book": {"isbn": ["ghi"]}, "rating": {"id": [3]}},
             "copyright": None,
             "description": "Rabbits on the run",
             "isbn": "ghi",
@@ -534,9 +534,18 @@ def test_meta_keys(self, sync, data):
         sync.tree = Tree(sync.models, nodes)
         docs = [sort_list(doc) for doc in sync.sync()]
         sources = {doc["_id"]: doc["_source"] for doc in docs}
-        assert sources["abc"]["_meta"] == {"rating": {"id": [1]}}
-        assert sources["def"]["_meta"] == {"rating": {"id": [2]}}
-        assert sources["ghi"]["_meta"] == {"rating": {"id": [3]}}
+        assert sources["abc"]["_meta"] == {
+            "book": {"isbn": ["abc"]},
+            "rating": {"id": [1]},
+        }
+        assert sources["def"]["_meta"] == {
+            "book": {"isbn": ["def"]},
+            "rating": {"id": [2]},
+        }
+        assert sources["ghi"]["_meta"] == {
+            "book": {"isbn": ["ghi"]},
+            "rating": {"id": [3]},
+        }
         assert_resync_empty(sync, nodes)
 
     def test_missing_foreign_keys(self, sync, data):
@@ -602,19 +611,19 @@ def test_update_primary_key_non_concurrent(
 
         assert docs == [
             {
-                "_meta": {"rating": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "rating": {"id": [1]}},
                 "isbn": "abc",
                 "rating": {"id": 1, "value": 1.1},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"rating": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "rating": {"id": [2]}},
                 "isbn": "def",
                 "rating": {"id": 2, "value": 2.2},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"rating": {"id": [3]}},
+                "_meta": {"book": {"isbn": ["ghi"]}, "rating": {"id": [3]}},
                 "isbn": "ghi",
                 "rating": {"id": 3, "value": 3.3},
                 "title": "The Rabbit Club",
@@ -644,25 +653,25 @@ def test_update_primary_key_non_concurrent(
         docs = search(sync.search_client, "testdb")
         assert docs == [
             {
-                "_meta": {"rating": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "rating": {"id": [1]}},
                 "isbn": "abc",
                 "rating": {"id": 1, "value": 1.1},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"rating": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "rating": {"id": [2]}},
                 "isbn": "def",
                 "rating": {"id": 2, "value": 2.2},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {},
+                "_meta": {"book": {"isbn": ["ghi"]}},
                 "isbn": "ghi",
                 "rating": None,
                 "title": "The Rabbit Club",
             },
             {
-                "_meta": {"rating": {"id": [3]}},
+                "_meta": {"book": {"isbn": ["xyz"]}, "rating": {"id": [3]}},
                 "isbn": "xyz",
                 "rating": {"id": 3, "value": 3.3},
                 "title": "Milli and the Ants",
@@ -700,19 +709,19 @@ def test_update_primary_key_concurrent(self, data, book_cls, rating_cls):
 
         assert docs == [
             {
-                "_meta": {"rating": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "rating": {"id": [1]}},
                 "isbn": "abc",
                 "rating": {"id": 1, "value": 1.1},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"rating": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "rating": {"id": [2]}},
                 "isbn": "def",
                 "rating": {"id": 2, "value": 2.2},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"rating": {"id": [3]}},
+                "_meta": {"book": {"isbn": ["ghi"]}, "rating": {"id": [3]}},
                 "isbn": "ghi",
                 "rating": {"id": 3, "value": 3.3},
                 "title": "The Rabbit Club",
@@ -764,25 +773,25 @@ def poll_db():
         docs = search(sync.search_client, "testdb")
         assert docs == [
             {
-                "_meta": {"rating": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "rating": {"id": [1]}},
                 "isbn": "abc",
                 "rating": {"id": 1, "value": 1.1},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"rating": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "rating": {"id": [2]}},
                 "isbn": "def",
                 "rating": {"id": 2, "value": 2.2},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {},
+                "_meta": {"book": {"isbn": ["ghi"]}},
                 "isbn": "ghi",
                 "rating": None,
                 "title": "The Rabbit Club",
             },
             {
-                "_meta": {"rating": {"id": [3]}},
+                "_meta": {"book": {"isbn": ["xyz"]}, "rating": {"id": [3]}},
                 "isbn": "xyz",
                 "rating": {"id": 3, "value": 3.3},
                 "title": "Milli and the Ants",
@@ -820,19 +829,19 @@ def test_insert_non_concurrent(self, data, book_cls, rating_cls):
         docs = search(sync.search_client, "testdb")
         assert docs == [
             {
-                "_meta": {"rating": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "rating": {"id": [1]}},
                 "isbn": "abc",
                 "rating": {"id": 1, "value": 1.1},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"rating": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "rating": {"id": [2]}},
                 "isbn": "def",
                 "rating": {"id": 2, "value": 2.2},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"rating": {"id": [3]}},
+                "_meta": {"book": {"isbn": ["ghi"]}, "rating": {"id": [3]}},
                 "isbn": "ghi",
                 "rating": {"id": 3, "value": 3.3},
                 "title": "The Rabbit Club",
@@ -865,25 +874,25 @@ def test_insert_non_concurrent(self, data, book_cls, rating_cls):
 
         assert docs == [
             {
-                "_meta": {"rating": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "rating": {"id": [1]}},
                 "isbn": "abc",
                 "rating": {"id": 1, "value": 1.1},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"rating": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "rating": {"id": [2]}},
                 "isbn": "def",
                 "rating": {"id": 2, "value": 2.2},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"rating": {"id": [3]}},
+                "_meta": {"book": {"isbn": ["ghi"]}, "rating": {"id": [3]}},
                 "isbn": "ghi",
                 "rating": {"id": 3, "value": 3.3},
                 "title": "The Rabbit Club",
             },
             {
-                "_meta": {"rating": {"id": [99]}},
+                "_meta": {"book": {"isbn": ["xyz"]}, "rating": {"id": [99]}},
                 "isbn": "xyz",
                 "rating": {"id": 99, "value": 4.4},
                 "title": "Encyclopedia",
@@ -922,19 +931,19 @@ def test_update_non_primary_key_non_concurrent(
 
         assert docs == [
             {
-                "_meta": {"rating": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "rating": {"id": [1]}},
                 "isbn": "abc",
                 "rating": {"id": 1, "value": 1.1},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"rating": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "rating": {"id": [2]}},
                 "isbn": "def",
                 "rating": {"id": 2, "value": 2.2},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"rating": {"id": [3]}},
+                "_meta": {"book": {"isbn": ["ghi"]}, "rating": {"id": [3]}},
                 "isbn": "ghi",
                 "rating": {"id": 3, "value": 3.3},
                 "title": "The Rabbit Club",
@@ -961,19 +970,19 @@ def test_update_non_primary_key_non_concurrent(
 
         assert docs == [
             {
-                "_meta": {"rating": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "rating": {"id": [1]}},
                 "isbn": "abc",
                 "rating": {"id": 1, "value": 1.1},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"rating": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "rating": {"id": [2]}},
                 "isbn": "def",
                 "rating": {"id": 2, "value": 2.2},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"rating": {"id": [3]}},
+                "_meta": {"book": {"isbn": ["ghi"]}, "rating": {"id": [3]}},
                 "isbn": "ghi",
                 "rating": {"id": 3, "value": 4.4},
                 "title": "The Rabbit Club",
@@ -1012,19 +1021,19 @@ def test_update_non_primary_key_concurrent(
 
         assert docs == [
             {
-                "_meta": {"rating": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "rating": {"id": [1]}},
                 "isbn": "abc",
                 "rating": {"id": 1, "value": 1.1},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"rating": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "rating": {"id": [2]}},
                 "isbn": "def",
                 "rating": {"id": 2, "value": 2.2},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"rating": {"id": [3]}},
+                "_meta": {"book": {"isbn": ["ghi"]}, "rating": {"id": [3]}},
                 "isbn": "ghi",
                 "rating": {"id": 3, "value": 3.3},
                 "title": "The Rabbit Club",
@@ -1068,19 +1077,19 @@ def poll_db():
 
         assert docs == [
             {
-                "_meta": {"rating": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "rating": {"id": [1]}},
                 "isbn": "abc",
                 "rating": {"id": 1, "value": 1.1},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"rating": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "rating": {"id": [2]}},
                 "isbn": "def",
                 "rating": {"id": 2, "value": 2.2},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"rating": {"id": [3]}},
+                "_meta": {"book": {"isbn": ["ghi"]}, "rating": {"id": [3]}},
                 "isbn": "ghi",
                 "rating": {"id": 3, "value": 4.4},
                 "title": "The Rabbit Club",
@@ -1118,19 +1127,19 @@ def test_delete_concurrent(self, data, book_cls, rating_cls):
 
         assert docs == [
             {
-                "_meta": {"rating": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "rating": {"id": [1]}},
                 "isbn": "abc",
                 "rating": {"id": 1, "value": 1.1},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"rating": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "rating": {"id": [2]}},
                 "isbn": "def",
                 "rating": {"id": 2, "value": 2.2},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"rating": {"id": [3]}},
+                "_meta": {"book": {"isbn": ["ghi"]}, "rating": {"id": [3]}},
                 "isbn": "ghi",
                 "rating": {"id": 3, "value": 3.3},
                 "title": "The Rabbit Club",
@@ -1187,19 +1196,19 @@ def poll_db():
         docs = search(sync.search_client, "testdb")
         assert docs == [
             {
-                "_meta": {"rating": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "rating": {"id": [1]}},
                 "isbn": "abc",
                 "rating": {"id": 1, "value": 1.1},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"rating": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "rating": {"id": [2]}},
                 "isbn": "def",
                 "rating": {"id": 2, "value": 2.2},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"rating": {"id": [3]}},
+                "_meta": {"book": {"isbn": ["xyz"]}, "rating": {"id": [3]}},
                 "isbn": "xyz",
                 "rating": {"id": 3, "value": 3.3},
                 "title": "The End of time",
diff --git a/tests/test_sync_single_child_fk_on_parent.py b/tests/test_sync_single_child_fk_on_parent.py
index 6490183..9ba7bb1 100644
--- a/tests/test_sync_single_child_fk_on_parent.py
+++ b/tests/test_sync_single_child_fk_on_parent.py
@@ -107,7 +107,7 @@ def test_relationship_object_one_to_one(self, sync, data):
         docs = [sort_list(doc) for doc in sync.sync()]
         assert docs[0]["_id"] == "abc"
         assert docs[0]["_source"] == {
-            "_meta": {"publisher": {"id": [1]}},
+            "_meta": {"book": {"isbn": ["abc"]}, "publisher": {"id": [1]}},
             "description": "Tigers are fierce creatures",
             "isbn": "abc",
             "publisher": {"id": 1, "name": "Tiger publishing"},
@@ -116,7 +116,7 @@ def test_relationship_object_one_to_one(self, sync, data):
 
         assert docs[1]["_id"] == "def"
         assert docs[1]["_source"] == {
-            "_meta": {"publisher": {"id": [2]}},
+            "_meta": {"book": {"isbn": ["def"]}, "publisher": {"id": [2]}},
             "description": "Lion and the mouse",
             "isbn": "def",
             "publisher": {"id": 2, "name": "Lion publishing"},
@@ -125,7 +125,7 @@ def test_relationship_object_one_to_one(self, sync, data):
 
         assert docs[2]["_id"] == "ghi"
         assert docs[2]["_source"] == {
-            "_meta": {"publisher": {"id": [3]}},
+            "_meta": {"book": {"isbn": ["ghi"]}, "publisher": {"id": [3]}},
             "description": "Rabbits on the run",
             "isbn": "ghi",
             "publisher": {"id": 3, "name": "Hop Bunny publishing"},
@@ -154,7 +154,7 @@ def test_relationship_object_one_to_many(self, sync, data):
 
         assert docs[0]["_id"] == "abc"
         assert docs[0]["_source"] == {
-            "_meta": {"publisher": {"id": [1]}},
+            "_meta": {"book": {"isbn": ["abc"]}, "publisher": {"id": [1]}},
             "description": "Tigers are fierce creatures",
             "isbn": "abc",
             "publisher": [{"id": 1, "name": "Tiger publishing"}],
@@ -163,7 +163,7 @@ def test_relationship_object_one_to_many(self, sync, data):
 
         assert docs[1]["_id"] == "def"
         assert docs[1]["_source"] == {
-            "_meta": {"publisher": {"id": [2]}},
+            "_meta": {"book": {"isbn": ["def"]}, "publisher": {"id": [2]}},
             "description": "Lion and the mouse",
             "isbn": "def",
             "publisher": [{"id": 2, "name": "Lion publishing"}],
@@ -172,7 +172,7 @@ def test_relationship_object_one_to_many(self, sync, data):
 
         assert docs[2]["_id"] == "ghi"
         assert docs[2]["_source"] == {
-            "_meta": {"publisher": {"id": [3]}},
+            "_meta": {"book": {"isbn": ["ghi"]}, "publisher": {"id": [3]}},
             "description": "Rabbits on the run",
             "isbn": "ghi",
             "publisher": [{"id": 3, "name": "Hop Bunny publishing"}],
@@ -199,7 +199,7 @@ def test_relationship_scalar_one_to_one(self, sync, data):
         docs = [sort_list(doc) for doc in sync.sync()]
         assert docs[0]["_id"] == "abc"
         assert docs[0]["_source"] == {
-            "_meta": {"publisher": {"id": [1]}},
+            "_meta": {"book": {"isbn": ["abc"]}, "publisher": {"id": [1]}},
             "description": "Tigers are fierce creatures",
             "isbn": "abc",
             "publisher": "Tiger publishing",
@@ -208,7 +208,7 @@ def test_relationship_scalar_one_to_one(self, sync, data):
 
         assert docs[1]["_id"] == "def"
         assert docs[1]["_source"] == {
-            "_meta": {"publisher": {"id": [2]}},
+            "_meta": {"book": {"isbn": ["def"]}, "publisher": {"id": [2]}},
             "description": "Lion and the mouse",
             "isbn": "def",
             "publisher": "Lion publishing",
@@ -217,7 +217,7 @@ def test_relationship_scalar_one_to_one(self, sync, data):
 
         assert docs[2]["_id"] == "ghi"
         assert docs[2]["_source"] == {
-            "_meta": {"publisher": {"id": [3]}},
+            "_meta": {"book": {"isbn": ["ghi"]}, "publisher": {"id": [3]}},
             "description": "Rabbits on the run",
             "isbn": "ghi",
             "publisher": "Hop Bunny publishing",
@@ -245,7 +245,7 @@ def test_relationship_scalar_one_to_many(self, sync, data):
         docs = sorted(docs, key=lambda k: k["_id"])
         assert docs[0]["_id"] == "abc"
         assert docs[0]["_source"] == {
-            "_meta": {"publisher": {"id": [1]}},
+            "_meta": {"book": {"isbn": ["abc"]}, "publisher": {"id": [1]}},
             "description": "Tigers are fierce creatures",
             "isbn": "abc",
             "publisher": ["Tiger publishing"],
@@ -254,7 +254,7 @@ def test_relationship_scalar_one_to_many(self, sync, data):
 
         assert docs[1]["_id"] == "def"
         assert docs[1]["_source"] == {
-            "_meta": {"publisher": {"id": [2]}},
+            "_meta": {"book": {"isbn": ["def"]}, "publisher": {"id": [2]}},
             "description": "Lion and the mouse",
             "isbn": "def",
             "publisher": ["Lion publishing"],
@@ -263,7 +263,7 @@ def test_relationship_scalar_one_to_many(self, sync, data):
 
         assert docs[2]["_id"] == "ghi"
         assert docs[2]["_source"] == {
-            "_meta": {"publisher": {"id": [3]}},
+            "_meta": {"book": {"isbn": ["ghi"]}, "publisher": {"id": [3]}},
             "description": "Rabbits on the run",
             "isbn": "ghi",
             "publisher": ["Hop Bunny publishing"],
@@ -291,7 +291,7 @@ def test_label(self, sync, data):
         docs = [sort_list(doc) for doc in sync.sync()]
         assert docs[0]["_id"] == "abc"
         assert docs[0]["_source"] == {
-            "_meta": {"publisher": {"id": [1]}},
+            "_meta": {"book": {"isbn": ["abc"]}, "publisher": {"id": [1]}},
             "description": "Tigers are fierce creatures",
             "isbn": "abc",
             "publisher_x": "Tiger publishing",
@@ -300,7 +300,7 @@ def test_label(self, sync, data):
 
         assert docs[1]["_id"] == "def"
         assert docs[1]["_source"] == {
-            "_meta": {"publisher": {"id": [2]}},
+            "_meta": {"book": {"isbn": ["def"]}, "publisher": {"id": [2]}},
             "description": "Lion and the mouse",
             "isbn": "def",
             "publisher_x": "Lion publishing",
@@ -309,7 +309,7 @@ def test_label(self, sync, data):
 
         assert docs[2]["_id"] == "ghi"
         assert docs[2]["_source"] == {
-            "_meta": {"publisher": {"id": [3]}},
+            "_meta": {"book": {"isbn": ["ghi"]}, "publisher": {"id": [3]}},
             "description": "Rabbits on the run",
             "isbn": "ghi",
             "publisher_x": "Hop Bunny publishing",
@@ -338,7 +338,7 @@ def test_null_label(self, sync, data):
         docs = [sort_list(doc) for doc in sync.sync()]
         assert docs[0]["_id"] == "abc"
         assert docs[0]["_source"] == {
-            "_meta": {"publisher": {"id": [1]}},
+            "_meta": {"book": {"isbn": ["abc"]}, "publisher": {"id": [1]}},
             "description": "Tigers are fierce creatures",
             "isbn": "abc",
             "publisher": "Tiger publishing",
@@ -375,7 +375,7 @@ def test_transform(self, sync, data):
         docs = [sort_list(doc) for doc in sync.sync()]
         assert docs[0]["_id"] == "abc"
         assert docs[0]["_source"] == {
-            "_meta": {"publisher": {"id": [1]}},
+            "_meta": {"book": {"isbn": ["abc"]}, "publisher": {"id": [1]}},
             "book_isbn": "abc",
             "book_title": "The Tiger Club",
             "description": "Tigers are fierce creatures",
@@ -387,7 +387,7 @@ def test_transform(self, sync, data):
 
         assert docs[1]["_id"] == "def"
         assert docs[1]["_source"] == {
-            "_meta": {"publisher": {"id": [2]}},
+            "_meta": {"book": {"isbn": ["def"]}, "publisher": {"id": [2]}},
             "book_isbn": "def",
             "book_title": "The Lion Club",
             "description": "Lion and the mouse",
@@ -399,7 +399,7 @@ def test_transform(self, sync, data):
 
         assert docs[2]["_id"] == "ghi"
         assert docs[2]["_source"] == {
-            "_meta": {"publisher": {"id": [3]}},
+            "_meta": {"book": {"isbn": ["ghi"]}, "publisher": {"id": [3]}},
             "book_isbn": "ghi",
             "book_title": "The Rabbit Club",
             "description": "Rabbits on the run",
@@ -455,7 +455,7 @@ def test_schema_with_no_column_specified(self, sync, data):
         sync.tree = Tree(sync.models, nodes)
         docs = [sort_list(doc) for doc in sync.sync()]
         assert docs[2]["_source"] == {
-            "_meta": {"publisher": {"id": [3]}},
+            "_meta": {"book": {"isbn": ["ghi"]}, "publisher": {"id": [3]}},
             "copyright": None,
             "description": "Rabbits on the run",
             "isbn": "ghi",
@@ -540,9 +540,18 @@ def test_meta_keys(self, sync, data):
         sync.tree = Tree(sync.models, nodes)
         docs = [sort_list(doc) for doc in sync.sync()]
         sources = {doc["_id"]: doc["_source"] for doc in docs}
-        assert sources["abc"]["_meta"] == {"publisher": {"id": [1]}}
-        assert sources["def"]["_meta"] == {"publisher": {"id": [2]}}
-        assert sources["ghi"]["_meta"] == {"publisher": {"id": [3]}}
+        assert sources["abc"]["_meta"] == {
+            "book": {"isbn": ["abc"]},
+            "publisher": {"id": [1]},
+        }
+        assert sources["def"]["_meta"] == {
+            "book": {"isbn": ["def"]},
+            "publisher": {"id": [2]},
+        }
+        assert sources["ghi"]["_meta"] == {
+            "book": {"isbn": ["ghi"]},
+            "publisher": {"id": [3]},
+        }
         assert_resync_empty(sync, nodes)
 
     def test_missing_foreign_keys(self, sync, data):
@@ -608,19 +617,19 @@ def test_update_primary_key_non_concurrent(
 
         assert docs == [
             {
-                "_meta": {"publisher": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "publisher": {"id": [1]}},
                 "isbn": "abc",
                 "publisher": {"id": 1, "name": "Tiger publishing"},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"publisher": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "publisher": {"id": [2]}},
                 "isbn": "def",
                 "publisher": {"id": 2, "name": "Lion publishing"},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"publisher": {"id": [3]}},
+                "_meta": {"book": {"isbn": ["ghi"]}, "publisher": {"id": [3]}},
                 "isbn": "ghi",
                 "publisher": {"id": 3, "name": "Hop Bunny publishing"},
                 "title": "The Rabbit Club",
@@ -651,19 +660,22 @@ def test_update_primary_key_non_concurrent(
 
         assert docs == [
             {
-                "_meta": {"publisher": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "publisher": {"id": [1]}},
                 "isbn": "abc",
                 "publisher": {"id": 1, "name": "Tiger publishing"},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"publisher": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "publisher": {"id": [2]}},
                 "isbn": "def",
                 "publisher": {"id": 2, "name": "Lion publishing"},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"publisher": {"id": [99]}},
+                "_meta": {
+                    "book": {"isbn": ["ghi"]},
+                    "publisher": {"id": [99]},
+                },
                 "isbn": "ghi",
                 "publisher": {"id": 99, "name": "Rabbit publishers"},
                 "title": "The Rabbit Club",
@@ -704,19 +716,19 @@ def test_update_primary_key_concurrent(
 
         assert docs == [
             {
-                "_meta": {"publisher": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "publisher": {"id": [1]}},
                 "isbn": "abc",
                 "publisher": {"id": 1, "name": "Tiger publishing"},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"publisher": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "publisher": {"id": [2]}},
                 "isbn": "def",
                 "publisher": {"id": 2, "name": "Lion publishing"},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"publisher": {"id": [3]}},
+                "_meta": {"book": {"isbn": ["ghi"]}, "publisher": {"id": [3]}},
                 "isbn": "ghi",
                 "publisher": {"id": 3, "name": "Hop Bunny publishing"},
                 "title": "The Rabbit Club",
@@ -768,19 +780,22 @@ def poll_db():
 
         assert docs == [
             {
-                "_meta": {"publisher": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "publisher": {"id": [1]}},
                 "isbn": "abc",
                 "publisher": {"id": 1, "name": "Tiger publishing"},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"publisher": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "publisher": {"id": [2]}},
                 "isbn": "def",
                 "publisher": {"id": 2, "name": "Lion publishing"},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"publisher": {"id": [99]}},
+                "_meta": {
+                    "book": {"isbn": ["ghi"]},
+                    "publisher": {"id": [99]},
+                },
                 "isbn": "ghi",
                 "publisher": {"id": 99, "name": "Rabbit publishers"},
                 "title": "The Rabbit Club",
@@ -818,19 +833,19 @@ def test_insert_non_concurrent(self, data, book_cls, publisher_cls):
         docs = search(sync.search_client, "testdb")
         assert docs == [
             {
-                "_meta": {"publisher": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "publisher": {"id": [1]}},
                 "isbn": "abc",
                 "publisher": {"id": 1, "name": "Tiger publishing"},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"publisher": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "publisher": {"id": [2]}},
                 "isbn": "def",
                 "publisher": {"id": 2, "name": "Lion publishing"},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"publisher": {"id": [3]}},
+                "_meta": {"book": {"isbn": ["ghi"]}, "publisher": {"id": [3]}},
                 "isbn": "ghi",
                 "publisher": {"id": 3, "name": "Hop Bunny publishing"},
                 "title": "The Rabbit Club",
@@ -860,25 +875,28 @@ def test_insert_non_concurrent(self, data, book_cls, publisher_cls):
 
         assert docs == [
             {
-                "_meta": {"publisher": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "publisher": {"id": [1]}},
                 "isbn": "abc",
                 "publisher": {"id": 1, "name": "Tiger publishing"},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"publisher": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "publisher": {"id": [2]}},
                 "isbn": "def",
                 "publisher": {"id": 2, "name": "Lion publishing"},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"publisher": {"id": [3]}},
+                "_meta": {"book": {"isbn": ["ghi"]}, "publisher": {"id": [3]}},
                 "isbn": "ghi",
                 "publisher": {"id": 3, "name": "Hop Bunny publishing"},
                 "title": "The Rabbit Club",
             },
             {
-                "_meta": {"publisher": {"id": [99]}},
+                "_meta": {
+                    "book": {"isbn": ["xyz"]},
+                    "publisher": {"id": [99]},
+                },
                 "isbn": "xyz",
                 "publisher": {"id": 99, "name": "Rabbit publishers"},
                 "title": "Encyclopedia",
@@ -917,19 +935,19 @@ def test_update_non_primary_key_non_concurrent(
 
         assert docs == [
             {
-                "_meta": {"publisher": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "publisher": {"id": [1]}},
                 "isbn": "abc",
                 "publisher": {"id": 1, "name": "Tiger publishing"},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"publisher": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "publisher": {"id": [2]}},
                 "isbn": "def",
                 "publisher": {"id": 2, "name": "Lion publishing"},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"publisher": {"id": [3]}},
+                "_meta": {"book": {"isbn": ["ghi"]}, "publisher": {"id": [3]}},
                 "isbn": "ghi",
                 "publisher": {"id": 3, "name": "Hop Bunny publishing"},
                 "title": "The Rabbit Club",
@@ -956,19 +974,19 @@ def test_update_non_primary_key_non_concurrent(
 
         assert docs == [
             {
-                "_meta": {"publisher": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "publisher": {"id": [1]}},
                 "isbn": "abc",
                 "publisher": {"id": 1, "name": "Tiger publishing"},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"publisher": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "publisher": {"id": [2]}},
                 "isbn": "def",
                 "publisher": {"id": 2, "name": "Lion publishing"},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"publisher": {"id": [3]}},
+                "_meta": {"book": {"isbn": ["ghi"]}, "publisher": {"id": [3]}},
                 "isbn": "ghi",
                 "publisher": {"id": 3, "name": "Rabbit publishers"},
                 "title": "The Rabbit Club",
@@ -1007,19 +1025,19 @@ def test_update_non_primary_key_concurrent(
 
         assert docs == [
             {
-                "_meta": {"publisher": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "publisher": {"id": [1]}},
                 "isbn": "abc",
                 "publisher": {"id": 1, "name": "Tiger publishing"},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"publisher": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "publisher": {"id": [2]}},
                 "isbn": "def",
                 "publisher": {"id": 2, "name": "Lion publishing"},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"publisher": {"id": [3]}},
+                "_meta": {"book": {"isbn": ["ghi"]}, "publisher": {"id": [3]}},
                 "isbn": "ghi",
                 "publisher": {"id": 3, "name": "Hop Bunny publishing"},
                 "title": "The Rabbit Club",
@@ -1063,19 +1081,19 @@ def poll_db():
 
         assert docs == [
             {
-                "_meta": {"publisher": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "publisher": {"id": [1]}},
                 "isbn": "abc",
                 "publisher": {"id": 1, "name": "Tiger publishing"},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"publisher": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "publisher": {"id": [2]}},
                 "isbn": "def",
                 "publisher": {"id": 2, "name": "Lion publishing"},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"publisher": {"id": [3]}},
+                "_meta": {"book": {"isbn": ["ghi"]}, "publisher": {"id": [3]}},
                 "isbn": "ghi",
                 "publisher": {"id": 3, "name": "Rabbit publishers"},
                 "title": "The Rabbit Club",
@@ -1113,19 +1131,19 @@ def test_delete_concurrent(self, data, book_cls, publisher_cls):
 
         assert docs == [
             {
-                "_meta": {"publisher": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "publisher": {"id": [1]}},
                 "isbn": "abc",
                 "publisher": {"id": 1, "name": "Tiger publishing"},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"publisher": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "publisher": {"id": [2]}},
                 "isbn": "def",
                 "publisher": {"id": 2, "name": "Lion publishing"},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"publisher": {"id": [3]}},
+                "_meta": {"book": {"isbn": ["ghi"]}, "publisher": {"id": [3]}},
                 "isbn": "ghi",
                 "publisher": {"id": 3, "name": "Hop Bunny publishing"},
                 "title": "The Rabbit Club",
@@ -1182,19 +1200,22 @@ def poll_db():
 
         assert docs == [
             {
-                "_meta": {"publisher": {"id": [1]}},
+                "_meta": {"book": {"isbn": ["abc"]}, "publisher": {"id": [1]}},
                 "isbn": "abc",
                 "publisher": {"id": 1, "name": "Tiger publishing"},
                 "title": "The Tiger Club",
             },
             {
-                "_meta": {"publisher": {"id": [2]}},
+                "_meta": {"book": {"isbn": ["def"]}, "publisher": {"id": [2]}},
                 "isbn": "def",
                 "publisher": {"id": 2, "name": "Lion publishing"},
                 "title": "The Lion Club",
             },
             {
-                "_meta": {"publisher": {"id": [99]}},
+                "_meta": {
+                    "book": {"isbn": ["ghi"]},
+                    "publisher": {"id": [99]},
+                },
                 "isbn": "ghi",
                 "publisher": {"id": 99, "name": "Rabbit publishers"},
                 "title": "The Rabbit Club",
diff --git a/tests/test_unique_behaviour.py b/tests/test_unique_behaviour.py
index 2d24499..637ff93 100644
--- a/tests/test_unique_behaviour.py
+++ b/tests/test_unique_behaviour.py
@@ -220,6 +220,7 @@ def test_sync_multiple_children_empty_leaf(
                 "_index": "testdb",
                 "_source": {
                     "_meta": {
+                        "book": {"isbn": ["abc"]},
                         "contact": {"id": [1, 2]},
                         "user": {"id": [1, 2]},
                     },