Fix validation for DataFrame with only time column in dataframe_to_tsfile

python/tests/test_to_tsfile.py

@@ -296,6 +296,20 @@ def test_dataframe_to_tsfile_no_data_columns():
             os.remove(tsfile_path)
 
 
+def test_dataframe_to_tsfile_only_time_column_raises():
+    """Only time column (no FIELD/TAG columns) must raise ValueError."""
+    tsfile_path = "test_only_time_column.tsfile"
+    try:
+        if os.path.exists(tsfile_path):
+            os.remove(tsfile_path)
+        df = pd.DataFrame({"time": [1, 2, 3]})
+        with pytest.raises(ValueError, match="at least one data column besides the time column"):
+            dataframe_to_tsfile(df, tsfile_path)
+    finally:
+        if os.path.exists(tsfile_path):
+            os.remove(tsfile_path)
+
+
 def test_dataframe_to_tsfile_time_column_not_found():
     tsfile_path = "test_dataframe_to_tsfile_time_err.tsfile"
     try:

python/tsfile/utils.py

@@ -287,7 +287,8 @@ def dataframe_to_tsfile(dataframe: pd.DataFrame,
         category = ColumnCategory.TAG if col in tag_columns_lower else ColumnCategory.FIELD
         column_schemas.append(ColumnSchema(col, ts_data_type, category))
 
-    if len(column_schemas) == 0:
+    data_columns = [s for s in column_schemas if s.get_category() != ColumnCategory.TIME]
+    if len(data_columns) == 0:
         raise ValueError("DataFrame must have at least one data column besides the time column")
 
     table_schema = TableSchema(table_name, column_schemas)