use 'insert' to ensure the replaced column ends up in the right position

Author: Tishj

src/duckdb_py/pyresult.cpp

@@ -298,7 +298,7 @@ void DuckDBPyResult::ChangeToTZType(PandasDataFrame &df) {
 			auto new_value = utc_local.attr("dt").attr("tz_convert")(result->client_properties.time_zone);
 			// We need to create the column anew because the exact dt changed to a new timezone
 			df.attr("drop")("columns"_a = names[i].c_str(), "inplace"_a = true);
-			df.attr("__setitem__")(names[i].c_str(), new_value);
+			df.attr("insert")(i, names[i].c_str(), new_value);
 		}
 	}
 }
@@ -384,7 +384,7 @@ PandasDataFrame DuckDBPyResult::FrameFromNumpy(bool date_as_object, const py::ha
 			if (result->types[i] == LogicalType::DATE) {
 				auto new_value = df[names[i].c_str()].attr("dt").attr("date");
 				df.attr("drop")("columns"_a = names[i].c_str(), "inplace"_a = true);
-				df.attr("__setitem__")(names[i].c_str(), new_value);
+				df.attr("insert")(i, names[i].c_str(), new_value);
 			}
 		}
 	}

tests/fast/pandas/test_column_order.py

@@ -0,0 +1,17 @@
+import pytest
+
+import pandas as pd
+import duckdb
+
+class TestColumnOrder:
+	def test_column_order(self, duckdb_cursor):
+		to_execute = """
+		CREATE OR REPLACE TABLE t1 AS (
+			SELECT NULL AS col1,
+			NULL::TIMESTAMPTZ AS timepoint,
+		);
+		SELECT timepoint, col1 FROM t1;
+		"""
+		df = duckdb.execute(to_execute).fetchdf()
+		cols = list(df.columns)
+		assert cols == ['timepoint', 'col1']