Ensure deduplication is disabled when range_start=='open'

dlt/extract/incremental/transform.py

@@ -117,6 +117,8 @@ def __call__(
     def deduplication_disabled(self) -> bool:
         """Skip deduplication when length of the key is 0 or if lag is applied."""
         # disable deduplication if end value is set - state is not saved
+        if self.range_start == "open":
+            return True
         if self.end_value is not None:
             return True
         # disable deduplication if lag is applied - destination must deduplicate ranges
@@ -232,6 +234,7 @@ def __call__(
         # new_value is "less" or equal to last_value (the actual max)
         if last_value == new_value:
             if self.range_start == "open":
+                # We only want greater than last_value
                 return None, False, False
             # use func to compute row_value into last_value compatible
             processed_row_value = last_value_func((row_value,))

tests/extract/test_incremental.py

@@ -3896,6 +3896,32 @@ def some_data(
     assert items == expected_items
 
 
+@pytest.mark.parametrize("item_type", ALL_TEST_DATA_ITEM_FORMATS)
+def test_start_range_open_no_deduplication(item_type: TestDataItemFormat) -> None:
+    @dlt.source
+    def dummy():
+        @dlt.resource
+        def some_data(
+            updated_at: dlt.sources.incremental[int] = dlt.sources.incremental(
+                "updated_at",
+                range_start="open",
+            )
+        ):
+            yield [{"updated_at": i} for i in range(3)]
+
+        yield some_data
+
+    pipeline = dlt.pipeline(pipeline_name=uniq_id())
+    pipeline.extract(dummy())
+
+    state = pipeline.state["sources"]["dummy"]["resources"]["some_data"]["incremental"][
+        "updated_at"
+    ]
+
+    # No unique values should be computed
+    assert state["unique_hashes"] == []
+
+
 @pytest.mark.parametrize("item_type", ALL_TEST_DATA_ITEM_FORMATS)
 @pytest.mark.parametrize("last_value_func", [min, max])
 def test_end_range_closed(item_type: TestDataItemFormat, last_value_func: Any) -> None: