test: add e2e case for timestamptz on restful (#46254)

Issue: #46253

 On branch feature/timestamps
 Changes to be committed:
	new file:   testcases/test_timestamptz.py

Signed-off-by: Eric Hou <eric.hou@zilliz.com>
Co-authored-by: Eric Hou <eric.hou@zilliz.com>

tests/restful_client_v2/testcases/test_timestamptz.py

@@ -0,0 +1,106 @@
+import time
+import random
+import pytest
+from datetime import datetime, timezone, timedelta
+
+from base.testbase import TestBase
+from utils.utils import gen_collection_name
+from utils.util_log import test_log as logger
+
+
+@pytest.mark.L1
+class TestTimestamptz(TestBase):
+    """
+    RESTful e2e coverage for timestamptz field:
+    - create collection with default timestamptz
+    - describe schema to confirm defaultValue
+    - insert rows (one missing timestamptz -> use default)
+    - flush + load
+    - get entities and validate timestamptz values are preserved/defaulted
+    """
+
+    def test_timestamptz_default_value_and_get(self):
+        name = gen_collection_name()
+        dim = 5
+        default_time = "2025-01-01T00:00:00Z"
+
+        # 1. create collection with timestamptz default value and vector index
+        payload = {
+            "collectionName": name,
+            "schema": {
+                "autoId": False,
+                "enableDynamicField": False,
+                "fields": [
+                    {"fieldName": "id", "dataType": "Int64", "isPrimary": True},
+                    {"fieldName": "time", "dataType": "Timestamptz", "defaultValue": default_time, "nullable": True},
+                    {"fieldName": "color", "dataType": "VarChar", "elementTypeParams": {"max_length": "30"}},
+                    {"fieldName": "vector", "dataType": "FloatVector", "elementTypeParams": {"dim": f"{dim}"}},
+                ],
+            },
+            "indexParams": [
+                {"fieldName": "vector", "indexName": "vector_index", "metricType": "L2"},
+            ],
+        }
+        logger.info(f"create collection {name} with payload: {payload}")
+        rsp = self.collection_client.collection_create(payload)
+        assert rsp["code"] == 0
+        self.wait_load_completed(name)
+
+        # 2. describe collection and verify defaultValue is returned
+        desc = self.collection_client.collection_describe(name)
+        assert desc["code"] == 0
+        fields = desc.get("data", {}).get("fields", [])
+        time_field = next(
+            (f for f in fields if f.get("fieldName") == "time" or f.get("name") == "time"),
+            None,
+        )
+        assert time_field is not None, f"timestamptz field not found in describe: {desc}"
+        # defaultValue is returned in protobuf-like structure, keep loose check on the string payload
+        assert "defaultValue" in time_field
+
+        # 3. insert rows (one row omits timestamptz to trigger default)
+        now_utc = datetime.now(timezone.utc)
+        one_hour_ago = now_utc - timedelta(hours=1)
+        rows = [
+            {"id": 1, "time": now_utc.isoformat(), "color": "red_9392", "vector": [random.random() for _ in range(dim)]},
+            {"id": 3, "time": one_hour_ago.isoformat(), "color": "pink_9298", "vector": [random.random() for _ in range(dim)]},
+            {"id": 4, "color": "green_0004", "vector": [random.random() for _ in range(dim)]},  # default timestamptz
+            {"id": 504, "time": one_hour_ago.isoformat(), "color": "blue_0000", "vector": [random.random() for _ in range(dim)]},
+        ]
+        insert_payload = {"collectionName": name, "data": rows}
+        insert_rsp = self.vector_client.vector_insert(insert_payload)
+        assert insert_rsp["code"] == 0
+        assert insert_rsp["data"]["insertCount"] == len(rows)
+
+        # 4. flush and load collection to make data queryable
+        flush_rsp = self.collection_client.flush(name)
+        assert flush_rsp["code"] == 0
+        load_rsp = self.collection_client.collection_load(collection_name=name)
+        assert load_rsp["code"] == 0
+        # wait a moment for load state
+        time.sleep(2)
+
+        # 5. get entities by id and validate timestamptz values
+        get_payload = {
+            "collectionName": name,
+            "id": [1, 3, 4],
+            "outputFields": ["color", "time"],
+        }
+        get_rsp = self.vector_client.vector_get(get_payload)
+        assert get_rsp["code"] == 0
+        result = {int(item["id"]): item for item in get_rsp["data"]}
+        assert set(result.keys()) == {1, 3, 4}
+
+        def to_dt(ts: str) -> datetime:
+            return datetime.fromisoformat(ts.replace("Z", "+00:00"))
+
+        # default applied for id=4
+        assert to_dt(result[4]["time"]) == to_dt(default_time)
+        # provided values preserved (allow small drift if server trims precision)
+        assert abs((to_dt(result[1]["time"]) - now_utc).total_seconds()) < 1
+        assert abs((to_dt(result[3]["time"]) - one_hour_ago).total_seconds()) < 1
+        # colors round-trip
+        assert result[1]["color"] == "red_9392"
+        assert result[3]["color"] == "pink_9298"
+        assert result[4]["color"] == "green_0004"
+