diff --git a/crates/sparrow-compiler/src/ast_to_dfg.rs b/crates/sparrow-compiler/src/ast_to_dfg.rs
index 120c54be1..7c32c69e6 100644
--- a/crates/sparrow-compiler/src/ast_to_dfg.rs
+++ b/crates/sparrow-compiler/src/ast_to_dfg.rs
@@ -557,14 +557,27 @@ pub fn add_to_dfg(
                 //
                 // TODO: Flattening the window arguments is hacky and confusing. We should instead
                 // incorporate the tick directly into the function containing the window.
-                dfg.enter_env();
-                dfg.bind("$condition_input", args[1].inner().clone());
+                let window_arg = original_ast.map(|e| &e.args()[2]);
+                let (condition, duration) = match window_arg {
+                    Some(window) => {
+                        dfg.enter_env();
+                        dfg.bind("$condition_input", args[1].inner().clone());
 
-                let window = &original_ast.unwrap().args()[2];
-                let (condition, duration) =
-                    flatten_window_args_if_needed(window, dfg, data_context, diagnostics)?;
+                        let result =
+                            flatten_window_args_if_needed(window, dfg, data_context, diagnostics)?;
+                        dfg.exit_env();
+                        result
+                    }
+                    None => {
+                        // If `expr` is None, we're running the Python builder code,
+                        // which already flattened things.
+                        //
+                        // Note that this won't define the `condition_input` for the
+                        // purposes of ticks.
+                        (args[2].clone(), args[3].clone())
+                    }
+                };
 
-                dfg.exit_env();
                 // [max, input, condition, duration]
                 vec![args[0].clone(), args[1].clone(), condition, duration]
             } else if function.name() == "when" || function.name() == "if" {
diff --git a/crates/sparrow-compiler/src/dfg.rs b/crates/sparrow-compiler/src/dfg.rs
index 37592f4f4..12bb91eaf 100644
--- a/crates/sparrow-compiler/src/dfg.rs
+++ b/crates/sparrow-compiler/src/dfg.rs
@@ -253,7 +253,7 @@ impl Dfg {
                     );
                 }
 
-                // 2. The number of argflatten_uments should be correct.
+                // 2. The number of args should be correct.
                 match expr {
                     Expression::Literal(_) | Expression::LateBound(_) => {
                         anyhow::ensure!(
diff --git a/crates/sparrow-compiler/src/functions/collection.rs b/crates/sparrow-compiler/src/functions/collection.rs
index f28129e9a..add4b2ae3 100644
--- a/crates/sparrow-compiler/src/functions/collection.rs
+++ b/crates/sparrow-compiler/src/functions/collection.rs
@@ -15,6 +15,9 @@ pub(super) fn register(registry: &mut Registry) {
 
     registry
         .register("collect<T: any>(const max: i64, input: T, window: window = null) -> list<T>")
+        .with_dfg_signature(
+            "collect<T: any>(const max: i64, input: T, window: bool = null, duration: i64 = null) -> list<T>",
+        )
         .with_implementation(Implementation::Instruction(InstOp::Collect))
         .set_internal();
 }
diff --git a/sparrow-py/pysrc/sparrow_py/__init__.py b/sparrow-py/pysrc/sparrow_py/__init__.py
index 38add032a..378bbfdc0 100644
--- a/sparrow-py/pysrc/sparrow_py/__init__.py
+++ b/sparrow-py/pysrc/sparrow_py/__init__.py
@@ -1,7 +1,7 @@
 """Kaskada query builder and local executon engine."""
 from typing import Dict
-from typing import Union
 from typing import List
+from typing import Union
 
 from ._windows import SinceWindow
 from ._windows import SlidingWindow
diff --git a/sparrow-py/pysrc/sparrow_py/expr.py b/sparrow-py/pysrc/sparrow_py/expr.py
index ae88392b3..ccdc459bf 100644
--- a/sparrow-py/pysrc/sparrow_py/expr.py
+++ b/sparrow-py/pysrc/sparrow_py/expr.py
@@ -287,6 +287,11 @@ def is_not_null(self) -> "Expr":
         """Return a boolean expression indicating if the expression is not null."""
         return Expr.call("is_valid", self)
 
+    def collect(
+        self, max: Optional[int] = None, window: Optional[Window] = None
+    ) -> "Expr":
+        return _aggregation("collect", self, window, max)
+
     def sum(self, window: Optional[Window] = None) -> "Expr":
         """Return the sum aggregation of the expression."""
         return _aggregation("sum", self, window)
@@ -312,13 +317,37 @@ def run_to_csv_string(self) -> str:
         return self.run().to_csv(index=False)
 
 
-def _aggregation(op: str, input: Expr, window: Optional[Window]) -> Expr:
-    """Create an aggregation with the given operation and input."""
+def _aggregation(
+    op: str, input: Expr, window: Optional[Window], *args: Optional[Arg]
+) -> Expr:
+    """
+    Creates an aggregation.
+
+    Parameters
+    ----------
+    op : str
+        The operation to create.
+    input : Expr
+        The input to the expression.
+    window : Optional[Window]
+      The window to use for the aggregation.
+    *args : Optional[Arg]
+        Additional arguments to provide before `input` and the flattened window.
+
+    Returns
+    -------
+    The resulting expression.
+    """
+
+    # Note: things would be easier if we had a more normal order, which
+    # we could do as part of "aligning" Sparrow signatures to the new direction.
+    # However, `collect` currently has `collect(max, input, window)`, requiring
+    # us to add the *args like so.
     if window is None:
-        return Expr.call(op, input, None, None)
+        return Expr.call(op, *args, input, None, None)
     elif isinstance(window, SinceWindow):
-        return Expr.call(op, input, window._predicate, 1)
+        return Expr.call(op, *args, input, window._predicate, None)
     elif isinstance(window, SlidingWindow):
-        return Expr.call(op, input, window._predicate, window._duration)
+        return Expr.call(op, *args, input, window._predicate, window._duration)
     else:
         raise ValueError(f"Unknown window type {window!r}")
diff --git a/sparrow-py/pytests/collect_test.py b/sparrow-py/pytests/collect_test.py
new file mode 100644
index 000000000..470d1a8a0
--- /dev/null
+++ b/sparrow-py/pytests/collect_test.py
@@ -0,0 +1,61 @@
+"""Tests for the collect function."""
+import pytest
+from sparrow_py import SinceWindow
+from sparrow_py import SlidingWindow
+from sparrow_py import record
+from sparrow_py.sources import CsvSource
+
+
+@pytest.fixture(scope="module")
+def source() -> CsvSource:
+    """Create an empty table for testing."""
+    content = "\n".join(
+        [
+            "time,key,m,n",
+            "1996-12-19T16:39:57-08:00,A,5,10",
+            "1996-12-19T16:39:58-08:00,B,24,3",
+            "1996-12-19T16:39:59-08:00,A,17,6",
+            "1996-12-19T16:40:00-08:00,A,,9",
+            "1996-12-19T16:40:01-08:00,A,12,",
+            "1996-12-19T16:40:02-08:00,A,,",
+        ]
+    )
+    return CsvSource("time", "key", content)
+
+
+def test_collect_basic(source, golden) -> None:
+    """Test we can collect values to a list"""
+    m = source["m"]
+    n = source["n"]
+    golden(
+        record(
+            {
+                "m": m,
+                "collect_m": m.collect(max=None),
+                "n": n,
+                "collect_n": n.collect(max=None),
+            }
+        )
+    )
+
+
+def test_collect_with_max(source, golden) -> None:
+    """Test we can collect values to a list with a max"""
+    m = source["m"]
+    n = source["n"]
+    golden(
+        record(
+            {
+                "m": m,
+                "collect_m_max_2": m.collect(max=2),
+                "n": n,
+                "collect_n_max_2": n.collect(max=2),
+            }
+        )
+    )
+
+
+def test_collect_since_window(source, golden) -> None:
+    """Test we can collect values to a list in a since window"""
+    m = source["m"]
+    golden(record({"m": m, "since_m": m.sum(window=SinceWindow(m > 10))}))
diff --git a/sparrow-py/pytests/conftest.py b/sparrow-py/pytests/conftest.py
index b0d4a03e6..3c549a5f6 100644
--- a/sparrow-py/pytests/conftest.py
+++ b/sparrow-py/pytests/conftest.py
@@ -27,9 +27,19 @@ def golden(request: pytest.FixtureRequest, pytestconfig: pytest.Config):
 
     def handler(
         query: sparrow_py.Expr,
-        format: Union[Literal["csv"], Literal["parquet"]] = "csv",
+        format: Union[Literal["csv"], Literal["parquet"], Literal["json"]] = "json",
     ):
-        """Check query results against a golden file."""
+        """
+        Check query results against a golden file.
+
+        Parameters
+        ----------
+        query : sparrow_py.Expr
+            The query to run.
+        format : str, optional
+            The format to store the golden file in.
+            Defaults to "json".
+        """
         nonlocal output
 
         df = query.run()
@@ -51,6 +61,8 @@ def handler(
                 df.to_csv(filename, index=False)
             elif format == "parquet":
                 df.to_parquet(filename)
+            elif format == "json":
+                df.to_json(filename, orient="records", lines=True)
             else:
                 raise ValueError(f"Unknown format {format}")
         else:
@@ -69,6 +81,10 @@ def handler(
             correct = pd.read_csv(filename, dtype=dtypes, parse_dates=parse_dates)
         elif format == "parquet":
             correct = pd.read_parquet(filename)
+        elif format == "json":
+            correct = pd.read_json(
+                filename, orient="records", lines=True, dtype=df.dtypes.to_dict()
+            )
         else:
             raise ValueError(f"Unknown format {format}")
         pd.testing.assert_frame_equal(df, correct)
diff --git a/sparrow-py/pytests/golden/aggregation_test/test_sum_unwindowed.csv b/sparrow-py/pytests/golden/aggregation_test/test_sum_unwindowed.csv
deleted file mode 100644
index 2b48f98e2..000000000
--- a/sparrow-py/pytests/golden/aggregation_test/test_sum_unwindowed.csv
+++ /dev/null
@@ -1,7 +0,0 @@
-_time,_subsort,_key_hash,_key,m,sum_m,n,sum_n
-1996-12-20 00:39:57,0,12960666915911099378,A,5.0,5,10.0,10
-1996-12-20 00:39:58,1,2867199309159137213,B,24.0,24,3.0,3
-1996-12-20 00:39:59,2,12960666915911099378,A,17.0,22,6.0,16
-1996-12-20 00:40:00,3,12960666915911099378,A,,22,9.0,25
-1996-12-20 00:40:01,4,12960666915911099378,A,12.0,34,,25
-1996-12-20 00:40:02,5,12960666915911099378,A,,34,,25
diff --git a/sparrow-py/pytests/golden/aggregation_test/test_sum_unwindowed.json b/sparrow-py/pytests/golden/aggregation_test/test_sum_unwindowed.json
new file mode 100644
index 000000000..64c3cdf4d
--- /dev/null
+++ b/sparrow-py/pytests/golden/aggregation_test/test_sum_unwindowed.json
@@ -0,0 +1,6 @@
+{"_time":851042397000,"_subsort":0,"_key_hash":12960666915911099378,"_key":"A","m":5.0,"sum_m":5,"n":10.0,"sum_n":10}
+{"_time":851042398000,"_subsort":1,"_key_hash":2867199309159137213,"_key":"B","m":24.0,"sum_m":24,"n":3.0,"sum_n":3}
+{"_time":851042399000,"_subsort":2,"_key_hash":12960666915911099378,"_key":"A","m":17.0,"sum_m":22,"n":6.0,"sum_n":16}
+{"_time":851042400000,"_subsort":3,"_key_hash":12960666915911099378,"_key":"A","m":null,"sum_m":22,"n":9.0,"sum_n":25}
+{"_time":851042401000,"_subsort":4,"_key_hash":12960666915911099378,"_key":"A","m":12.0,"sum_m":34,"n":null,"sum_n":25}
+{"_time":851042402000,"_subsort":5,"_key_hash":12960666915911099378,"_key":"A","m":null,"sum_m":34,"n":null,"sum_n":25}
diff --git a/sparrow-py/pytests/golden/aggregation_test/test_sum_windowed.csv b/sparrow-py/pytests/golden/aggregation_test/test_sum_windowed.csv
deleted file mode 100644
index d0207ce2c..000000000
--- a/sparrow-py/pytests/golden/aggregation_test/test_sum_windowed.csv
+++ /dev/null
@@ -1,7 +0,0 @@
-_time,_subsort,_key_hash,_key,m,sum_m,n,sum_n
-1996-12-20 00:39:57,0,12960666915911099378,A,5.0,5,10.0,10
-1996-12-20 00:39:58,1,2867199309159137213,B,24.0,24,3.0,3
-1996-12-20 00:39:59,2,12960666915911099378,A,17.0,22,6.0,16
-1996-12-20 00:40:00,3,12960666915911099378,A,,22,9.0,25
-1996-12-20 00:40:01,4,12960666915911099378,A,12.0,34,,25
-1996-12-20 00:40:02,5,12960666915911099378,A,,34,,9
diff --git a/sparrow-py/pytests/golden/aggregation_test/test_sum_windowed.json b/sparrow-py/pytests/golden/aggregation_test/test_sum_windowed.json
new file mode 100644
index 000000000..17bfd1c88
--- /dev/null
+++ b/sparrow-py/pytests/golden/aggregation_test/test_sum_windowed.json
@@ -0,0 +1,6 @@
+{"_time":851042397000,"_subsort":0,"_key_hash":12960666915911099378,"_key":"A","m":5.0,"sum_m":5,"n":10.0,"sum_n":10}
+{"_time":851042398000,"_subsort":1,"_key_hash":2867199309159137213,"_key":"B","m":24.0,"sum_m":24,"n":3.0,"sum_n":3}
+{"_time":851042399000,"_subsort":2,"_key_hash":12960666915911099378,"_key":"A","m":17.0,"sum_m":22,"n":6.0,"sum_n":16}
+{"_time":851042400000,"_subsort":3,"_key_hash":12960666915911099378,"_key":"A","m":null,"sum_m":22,"n":9.0,"sum_n":25}
+{"_time":851042401000,"_subsort":4,"_key_hash":12960666915911099378,"_key":"A","m":12.0,"sum_m":34,"n":null,"sum_n":25}
+{"_time":851042402000,"_subsort":5,"_key_hash":12960666915911099378,"_key":"A","m":null,"sum_m":34,"n":null,"sum_n":9}
diff --git a/sparrow-py/pytests/golden/collect_test/test_collect_basic.json b/sparrow-py/pytests/golden/collect_test/test_collect_basic.json
new file mode 100644
index 000000000..baa0e1e7c
--- /dev/null
+++ b/sparrow-py/pytests/golden/collect_test/test_collect_basic.json
@@ -0,0 +1,6 @@
+{"_time":851042397000,"_subsort":0,"_key_hash":12960666915911099378,"_key":"A","m":5.0,"collect_m":[5.0],"n":10.0,"collect_n":[10.0]}
+{"_time":851042398000,"_subsort":1,"_key_hash":2867199309159137213,"_key":"B","m":24.0,"collect_m":[24.0],"n":3.0,"collect_n":[3.0]}
+{"_time":851042399000,"_subsort":2,"_key_hash":12960666915911099378,"_key":"A","m":17.0,"collect_m":[5.0,17.0],"n":6.0,"collect_n":[10.0,6.0]}
+{"_time":851042400000,"_subsort":3,"_key_hash":12960666915911099378,"_key":"A","m":null,"collect_m":[5.0,17.0,null],"n":9.0,"collect_n":[10.0,6.0,9.0]}
+{"_time":851042401000,"_subsort":4,"_key_hash":12960666915911099378,"_key":"A","m":12.0,"collect_m":[5.0,17.0,null,12.0],"n":null,"collect_n":[10.0,6.0,9.0,null]}
+{"_time":851042402000,"_subsort":5,"_key_hash":12960666915911099378,"_key":"A","m":null,"collect_m":[5.0,17.0,null,12.0,null],"n":null,"collect_n":[10.0,6.0,9.0,null,null]}
diff --git a/sparrow-py/pytests/golden/collect_test/test_collect_since_window.json b/sparrow-py/pytests/golden/collect_test/test_collect_since_window.json
new file mode 100644
index 000000000..b1ce71f47
--- /dev/null
+++ b/sparrow-py/pytests/golden/collect_test/test_collect_since_window.json
@@ -0,0 +1,6 @@
+{"_time":851042397000,"_subsort":0,"_key_hash":12960666915911099378,"_key":"A","m":5.0,"since_m":5.0}
+{"_time":851042398000,"_subsort":1,"_key_hash":2867199309159137213,"_key":"B","m":24.0,"since_m":24.0}
+{"_time":851042399000,"_subsort":2,"_key_hash":12960666915911099378,"_key":"A","m":17.0,"since_m":22.0}
+{"_time":851042400000,"_subsort":3,"_key_hash":12960666915911099378,"_key":"A","m":null,"since_m":null}
+{"_time":851042401000,"_subsort":4,"_key_hash":12960666915911099378,"_key":"A","m":12.0,"since_m":12.0}
+{"_time":851042402000,"_subsort":5,"_key_hash":12960666915911099378,"_key":"A","m":null,"since_m":null}
diff --git a/sparrow-py/pytests/golden/collect_test/test_collect_with_max.json b/sparrow-py/pytests/golden/collect_test/test_collect_with_max.json
new file mode 100644
index 000000000..1006a8011
--- /dev/null
+++ b/sparrow-py/pytests/golden/collect_test/test_collect_with_max.json
@@ -0,0 +1,6 @@
+{"_time":851042397000,"_subsort":0,"_key_hash":12960666915911099378,"_key":"A","m":5.0,"collect_m_max_2":[5.0],"n":10.0,"collect_n_max_2":[10.0]}
+{"_time":851042398000,"_subsort":1,"_key_hash":2867199309159137213,"_key":"B","m":24.0,"collect_m_max_2":[24.0],"n":3.0,"collect_n_max_2":[3.0]}
+{"_time":851042399000,"_subsort":2,"_key_hash":12960666915911099378,"_key":"A","m":17.0,"collect_m_max_2":[5.0,17.0],"n":6.0,"collect_n_max_2":[10.0,6.0]}
+{"_time":851042400000,"_subsort":3,"_key_hash":12960666915911099378,"_key":"A","m":null,"collect_m_max_2":[17.0,null],"n":9.0,"collect_n_max_2":[6.0,9.0]}
+{"_time":851042401000,"_subsort":4,"_key_hash":12960666915911099378,"_key":"A","m":12.0,"collect_m_max_2":[null,12.0],"n":null,"collect_n_max_2":[9.0,null]}
+{"_time":851042402000,"_subsort":5,"_key_hash":12960666915911099378,"_key":"A","m":null,"collect_m_max_2":[12.0,null],"n":null,"collect_n_max_2":[null,null]}
diff --git a/sparrow-py/pytests/golden/math_test/test_math_int64.csv b/sparrow-py/pytests/golden/math_test/test_math_int64.csv
deleted file mode 100644
index c3aacb6d7..000000000
--- a/sparrow-py/pytests/golden/math_test/test_math_int64.csv
+++ /dev/null
@@ -1,7 +0,0 @@
-_time,_subsort,_key_hash,_key,m,n,add,sub
-1996-12-20 00:39:57,0,12960666915911099378,A,5.0,10.0,15.0,-5.0
-1996-12-20 00:39:58,1,2867199309159137213,B,24.0,3.0,27.0,21.0
-1996-12-20 00:39:59,2,12960666915911099378,A,17.0,6.0,23.0,11.0
-1996-12-20 00:40:00,3,12960666915911099378,A,,9.0,,
-1996-12-20 00:40:01,4,12960666915911099378,A,12.0,,,
-1996-12-20 00:40:02,5,12960666915911099378,A,,,,
diff --git a/sparrow-py/pytests/golden/math_test/test_math_int64.json b/sparrow-py/pytests/golden/math_test/test_math_int64.json
new file mode 100644
index 000000000..7d0599587
--- /dev/null
+++ b/sparrow-py/pytests/golden/math_test/test_math_int64.json
@@ -0,0 +1,6 @@
+{"_time":851042397000,"_subsort":0,"_key_hash":12960666915911099378,"_key":"A","m":5.0,"n":10.0,"add":15.0,"sub":-5.0}
+{"_time":851042398000,"_subsort":1,"_key_hash":2867199309159137213,"_key":"B","m":24.0,"n":3.0,"add":27.0,"sub":21.0}
+{"_time":851042399000,"_subsort":2,"_key_hash":12960666915911099378,"_key":"A","m":17.0,"n":6.0,"add":23.0,"sub":11.0}
+{"_time":851042400000,"_subsort":3,"_key_hash":12960666915911099378,"_key":"A","m":null,"n":9.0,"add":null,"sub":null}
+{"_time":851042401000,"_subsort":4,"_key_hash":12960666915911099378,"_key":"A","m":12.0,"n":null,"add":null,"sub":null}
+{"_time":851042402000,"_subsort":5,"_key_hash":12960666915911099378,"_key":"A","m":null,"n":null,"add":null,"sub":null}
diff --git a/sparrow-py/pytests/golden/record_test/test_extend_record.csv b/sparrow-py/pytests/golden/record_test/test_extend_record.csv
deleted file mode 100644
index 7cb7c4e4a..000000000
--- a/sparrow-py/pytests/golden/record_test/test_extend_record.csv
+++ /dev/null
@@ -1,7 +0,0 @@
-_time,_subsort,_key_hash,_key,add,time,key,m,n
-1996-12-20 00:39:57,0,12960666915911099378,A,15.0,1996-12-19T16:39:57-08:00,A,5.0,10.0
-1996-12-20 00:39:58,1,2867199309159137213,B,27.0,1996-12-19T16:39:58-08:00,B,24.0,3.0
-1996-12-20 00:39:59,2,12960666915911099378,A,23.0,1996-12-19T16:39:59-08:00,A,17.0,6.0
-1996-12-20 00:40:00,3,12960666915911099378,A,,1996-12-19T16:40:00-08:00,A,,9.0
-1996-12-20 00:40:01,4,12960666915911099378,A,,1996-12-19T16:40:01-08:00,A,12.0,
-1996-12-20 00:40:02,5,12960666915911099378,A,,1996-12-19T16:40:02-08:00,A,,
diff --git a/sparrow-py/pytests/golden/record_test/test_extend_record.json b/sparrow-py/pytests/golden/record_test/test_extend_record.json
new file mode 100644
index 000000000..77351f7a6
--- /dev/null
+++ b/sparrow-py/pytests/golden/record_test/test_extend_record.json
@@ -0,0 +1,6 @@
+{"_time":851042397000,"_subsort":0,"_key_hash":12960666915911099378,"_key":"A","add":15.0,"time":"1996-12-19T16:39:57-08:00","key":"A","m":5.0,"n":10.0}
+{"_time":851042398000,"_subsort":1,"_key_hash":2867199309159137213,"_key":"B","add":27.0,"time":"1996-12-19T16:39:58-08:00","key":"B","m":24.0,"n":3.0}
+{"_time":851042399000,"_subsort":2,"_key_hash":12960666915911099378,"_key":"A","add":23.0,"time":"1996-12-19T16:39:59-08:00","key":"A","m":17.0,"n":6.0}
+{"_time":851042400000,"_subsort":3,"_key_hash":12960666915911099378,"_key":"A","add":null,"time":"1996-12-19T16:40:00-08:00","key":"A","m":null,"n":9.0}
+{"_time":851042401000,"_subsort":4,"_key_hash":12960666915911099378,"_key":"A","add":null,"time":"1996-12-19T16:40:01-08:00","key":"A","m":12.0,"n":null}
+{"_time":851042402000,"_subsort":5,"_key_hash":12960666915911099378,"_key":"A","add":null,"time":"1996-12-19T16:40:02-08:00","key":"A","m":null,"n":null}
diff --git a/sparrow-py/pytests/golden/record_test/test_record.csv b/sparrow-py/pytests/golden/record_test/test_record.csv
deleted file mode 100644
index 531603deb..000000000
--- a/sparrow-py/pytests/golden/record_test/test_record.csv
+++ /dev/null
@@ -1,7 +0,0 @@
-_time,_subsort,_key_hash,_key,m,n
-1996-12-20 00:39:57,0,12960666915911099378,A,5.0,10.0
-1996-12-20 00:39:58,1,2867199309159137213,B,24.0,3.0
-1996-12-20 00:39:59,2,12960666915911099378,A,17.0,6.0
-1996-12-20 00:40:00,3,12960666915911099378,A,,9.0
-1996-12-20 00:40:01,4,12960666915911099378,A,12.0,
-1996-12-20 00:40:02,5,12960666915911099378,A,,
diff --git a/sparrow-py/pytests/golden/record_test/test_record.json b/sparrow-py/pytests/golden/record_test/test_record.json
new file mode 100644
index 000000000..56953ae2d
--- /dev/null
+++ b/sparrow-py/pytests/golden/record_test/test_record.json
@@ -0,0 +1,6 @@
+{"_time":851042397000,"_subsort":0,"_key_hash":12960666915911099378,"_key":"A","m":5.0,"n":10.0}
+{"_time":851042398000,"_subsort":1,"_key_hash":2867199309159137213,"_key":"B","m":24.0,"n":3.0}
+{"_time":851042399000,"_subsort":2,"_key_hash":12960666915911099378,"_key":"A","m":17.0,"n":6.0}
+{"_time":851042400000,"_subsort":3,"_key_hash":12960666915911099378,"_key":"A","m":null,"n":9.0}
+{"_time":851042401000,"_subsort":4,"_key_hash":12960666915911099378,"_key":"A","m":12.0,"n":null}
+{"_time":851042402000,"_subsort":5,"_key_hash":12960666915911099378,"_key":"A","m":null,"n":null}
diff --git a/sparrow-py/pytests/golden/record_test/test_select_record.csv b/sparrow-py/pytests/golden/record_test/test_select_record.csv
deleted file mode 100644
index 2b6ac21b2..000000000
--- a/sparrow-py/pytests/golden/record_test/test_select_record.csv
+++ /dev/null
@@ -1,7 +0,0 @@
-_time,_subsort,_key_hash,_key,time,key,m
-1996-12-20 00:39:57,0,12960666915911099378,A,1996-12-19T16:39:57-08:00,A,5.0
-1996-12-20 00:39:58,1,2867199309159137213,B,1996-12-19T16:39:58-08:00,B,24.0
-1996-12-20 00:39:59,2,12960666915911099378,A,1996-12-19T16:39:59-08:00,A,17.0
-1996-12-20 00:40:00,3,12960666915911099378,A,1996-12-19T16:40:00-08:00,A,
-1996-12-20 00:40:01,4,12960666915911099378,A,1996-12-19T16:40:01-08:00,A,12.0
-1996-12-20 00:40:02,5,12960666915911099378,A,1996-12-19T16:40:02-08:00,A,
diff --git a/sparrow-py/pytests/golden/record_test/test_select_record.json b/sparrow-py/pytests/golden/record_test/test_select_record.json
new file mode 100644
index 000000000..9a16276ab
--- /dev/null
+++ b/sparrow-py/pytests/golden/record_test/test_select_record.json
@@ -0,0 +1,6 @@
+{"_time":851042397000,"_subsort":0,"_key_hash":12960666915911099378,"_key":"A","time":"1996-12-19T16:39:57-08:00","key":"A","m":5.0}
+{"_time":851042398000,"_subsort":1,"_key_hash":2867199309159137213,"_key":"B","time":"1996-12-19T16:39:58-08:00","key":"B","m":24.0}
+{"_time":851042399000,"_subsort":2,"_key_hash":12960666915911099378,"_key":"A","time":"1996-12-19T16:39:59-08:00","key":"A","m":17.0}
+{"_time":851042400000,"_subsort":3,"_key_hash":12960666915911099378,"_key":"A","time":"1996-12-19T16:40:00-08:00","key":"A","m":null}
+{"_time":851042401000,"_subsort":4,"_key_hash":12960666915911099378,"_key":"A","time":"1996-12-19T16:40:01-08:00","key":"A","m":12.0}
+{"_time":851042402000,"_subsort":5,"_key_hash":12960666915911099378,"_key":"A","time":"1996-12-19T16:40:02-08:00","key":"A","m":null}