diff --git a/CHANGELOG.md b/CHANGELOG.md
index 335ebbd..c7cb8c7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,11 @@
 # Change Log
 All notable changes to this project will be documented in this file.
 
+## 2.1.3 - 2026-02
+ ### Runner
+ - Separate writer from runner, sorting schema to align to written table
+ - Added a debug run option that return dataframe without writing anything
+
 ## 2.1.2 - 2026-01
  ### Maker
  - Feature type normalization to Double and Long
diff --git a/pyproject.toml b/pyproject.toml
index f7eae2b..4a850c3 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "rialto"
-version = "2.1.2"
+version = "2.1.3"
 description = "Rialto is a framework for building and deploying machine learning features in a scalable and reusable way. It provides a set of tools that make it easy to define and deploy features and models, and it provides a way to orchestrate the execution of these features and models."
 authors = [
     { name = "Marek Dobransky", email = "marekdobr@gmail.com" },
diff --git a/rialto/common/utils.py b/rialto/common/utils.py
index 875ed7d..541e977 100644
--- a/rialto/common/utils.py
+++ b/rialto/common/utils.py
@@ -91,11 +91,11 @@ def normalize_types(df: DataFrame) -> DataFrame:
 
     return df.select(
         [
-            F.col(f.name).cast(DoubleType())
+            F.when(F.col(f.name).isNotNull(), F.col(f.name).cast(DoubleType())).otherwise(F.lit(None)).alias(f.name)
             if isinstance(f.dataType, float_types)
-            else F.col(f.name).cast(LongType())
+            else F.when(F.col(f.name).isNotNull(), F.col(f.name).cast(LongType())).otherwise(F.lit(None)).alias(f.name)
             if isinstance(f.dataType, int_types)
-            else F.col(f.name)
+            else F.when(F.col(f.name).isNotNull(), F.col(f.name)).otherwise(F.lit(None)).alias(f.name)
             for f in df.schema.fields
         ]
     )
diff --git a/rialto/runner/runner.py b/rialto/runner/runner.py
index e3d945c..2807a77 100644
--- a/rialto/runner/runner.py
+++ b/rialto/runner/runner.py
@@ -30,6 +30,7 @@
 from rialto.runner.reporting.tracker import Tracker
 from rialto.runner.table import Table
 from rialto.runner.transformation import Transformation
+from rialto.runner.writer import Writer
 
 
 class Runner:
@@ -52,7 +53,7 @@ def __init__(
         self.rerun = rerun
         self.skip_dependencies = skip_dependencies
         self.op = op
-        self.merge_schema = merge_schema
+        self.writer = Writer(spark, merge_schema=merge_schema)
         self.tracker = Tracker(
             mail_cfg=self.config.runner.mail, bookkeeping=self.config.runner.bookkeeping, spark=spark
         )
@@ -96,34 +97,6 @@ def _execute(self, instance: Transformation, run_date: date, pipeline: PipelineC
 
         return df
 
-    def _create_schema(self, table: Table):
-        """
-        Create schema if it doesn't exist
-
-        :param schema_path: path to schema
-        """
-        self.spark.sql(f"CREATE SCHEMA IF NOT EXISTS {table.get_schema_path()}")
-
-    def _write(self, df: DataFrame, info_date: date, table: Table) -> None:
-        """
-        Write dataframe to storage
-
-        :param df: dataframe to write
-        :param info_date: date to partition
-        :param table: path to write to
-        :return: None
-        """
-        self._create_schema(table)
-
-        df = df.withColumn(table.partition, F.lit(info_date))
-        if self.merge_schema is True:
-            df.write.partitionBy(table.partition).mode("overwrite").option("mergeSchema", "true").saveAsTable(
-                table.get_table_path()
-            )
-        else:
-            df.write.partitionBy(table.partition).mode("overwrite").saveAsTable(table.get_table_path())
-        logger.info(f"Results writen to {table.get_table_path()}")
-
     def _check_written(self, info_date: date, table: Table) -> int:
         """
         Check if there are records written for given date
@@ -238,7 +211,7 @@ def _run_one_date(self, pipeline: PipelineConfig, run_date: date, info_date: dat
 
             feature_group = utils.load_module(pipeline.module)
             df = self._execute(feature_group, run_date, pipeline)
-            self._write(df, info_date, target)
+            self.writer.write(df, info_date, target)
             records = self._check_written(info_date, target)
             logger.info(f"Generated {records} records")
             if records == 0:
@@ -331,3 +304,23 @@ def __call__(self):
             print(self.tracker.records)
             self.tracker.report_by_mail()
             logger.info("Execution finished")
+
+    def debug(self) -> DataFrame:
+        """Debug mode - run only first op for one date and return the resulting dataframe"""
+        logger.info("Running in debug mode")
+        if self.op:
+            pipeline = [p for p in self.config.pipelines if p.name == self.op][0]
+        else:
+            pipeline = self.config.pipelines[0]
+
+        target = Table(
+            schema_path=pipeline.target.target_schema,
+            class_name=pipeline.module.python_class,
+            partition=pipeline.target.target_partition_column,
+        )
+        selected_run_dates, selected_info_dates = self._select_run_dates(pipeline, target)
+        if len(selected_run_dates) > 0:
+            df = self._execute(utils.load_module(pipeline.module), selected_run_dates[0], pipeline)
+            return self.writer._process(df, selected_info_dates[0], target)
+        else:
+            logger.info("No dates to run in debug mode")
diff --git a/rialto/runner/writer.py b/rialto/runner/writer.py
new file mode 100644
index 0000000..3e31dac
--- /dev/null
+++ b/rialto/runner/writer.py
@@ -0,0 +1,96 @@
+#  Copyright 2022 ABSA Group Limited
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+
+__all__ = ["Writer"]
+
+from datetime import date
+from typing import List
+
+import pyspark.sql.functions as F
+from loguru import logger
+from pyspark.sql import DataFrame, SparkSession
+
+from rialto.runner.table import Table
+
+
+class Writer:
+    """Supporting class for runner"""
+
+    def __init__(self, spark: SparkSession, merge_schema=False):
+        self.spark = spark
+        self.merge_schema = merge_schema
+
+    def _create_schema(self, table: Table):
+        """
+        Create schema if it doesn't exist
+
+        :param schema_path: path to schema
+        """
+        self.spark.sql(f"CREATE SCHEMA IF NOT EXISTS {table.get_schema_path()}")
+
+    def _get_existing_columns(self, table: Table):
+        """
+        Get existing schema of table if it exists
+
+        :param table: table to check for
+        :return: existing columns or None
+        """
+        try:
+            return self.spark.table(table.get_table_path()).columns
+        except Exception as e:
+            logger.warning(f"Could not get existing schema for {table.get_table_path()}: {e}")
+            return None
+
+    def _align_schema(self, df: DataFrame, existing_columns: List) -> DataFrame:
+        """
+        Align schema of dataframe to existing schema of table if it exists
+
+        :param df: dataframe to align
+        :param table: table to check for existing schema
+        :return: dataframe with aligned schema
+        """
+        if existing_columns is not None:
+            return df.select(
+                *[F.col(c) for c in existing_columns if c in df.columns],
+                *[F.col(c) for c in df.columns if c not in existing_columns],
+            )
+        return df
+
+    def _process(self, df: DataFrame, info_date: date, table: Table) -> DataFrame:
+        df = df.withColumn(table.partition, F.lit(info_date))
+
+        df = self._align_schema(df, self._get_existing_columns(table))
+
+        return df
+
+    def write(self, df: DataFrame, info_date: date, table: Table) -> None:
+        """
+        Write dataframe to storage
+
+        :param df: dataframe to write
+        :param info_date: date to partition
+        :param table: path to write to
+        :return: None
+        """
+        self._create_schema(table)
+
+        df = self._process(df, info_date, table)
+
+        if self.merge_schema is True:
+            df.write.partitionBy(table.partition).mode("overwrite").option("mergeSchema", "true").saveAsTable(
+                table.get_table_path()
+            )
+        else:
+            df.write.partitionBy(table.partition).mode("overwrite").saveAsTable(table.get_table_path())
+        logger.info(f"Results writen to {table.get_table_path()}")
diff --git a/uv.lock b/uv.lock
index 7872703..eae6d1f 100644
--- a/uv.lock
+++ b/uv.lock
@@ -1078,7 +1078,7 @@ wheels = [
 
 [[package]]
 name = "rialto"
-version = "2.1.2"
+version = "2.1.3"
 source = { editable = "." }
 dependencies = [
     { name = "delta-spark" },