fix pandas tests

Author: evertlammerts

pyproject.toml

@@ -233,6 +233,9 @@ test = [ # dependencies used for running tests
     "pytest",
     "pytest-reraise",
     "pytest-timeout",
+    "pytest-xdist",
+    "pytest-randomly",
+    "pytest-timestamper",
     "mypy",
     "coverage",
     "gcovr",

src/duckdb_py/pyresult.cpp

@@ -23,6 +23,8 @@
 #include "duckdb/main/chunk_scan_state/query_result.hpp"
 #include "duckdb/common/arrow/arrow_query_result.hpp"
 
+using namespace pybind11::literals;
+
 namespace duckdb {
 
 DuckDBPyResult::DuckDBPyResult(unique_ptr<QueryResult> result_p) : result(std::move(result_p)) {
@@ -293,8 +295,10 @@ void DuckDBPyResult::ChangeToTZType(PandasDataFrame &df) {
 		if (result->types[i] == LogicalType::TIMESTAMP_TZ) {
 			// first localize to UTC then convert to timezone_config
 			auto utc_local = df[names[i].c_str()].attr("dt").attr("tz_localize")("UTC");
-			df.attr("__setitem__")(names[i].c_str(),
-			                       utc_local.attr("dt").attr("tz_convert")(result->client_properties.time_zone));
+			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);
 		}
 	}
 }
@@ -378,7 +382,9 @@ PandasDataFrame DuckDBPyResult::FrameFromNumpy(bool date_as_object, const py::ha
 	if (date_as_object) {
 		for (idx_t i = 0; i < result->ColumnCount(); i++) {
 			if (result->types[i] == LogicalType::DATE) {
-				df.attr("__setitem__")(names[i].c_str(), df[names[i].c_str()].attr("dt").attr("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);
 			}
 		}
 	}