Hi @Abdurrahman ,

To efficiently add a column to an existing Delta Lake table in a Databricks notebook when facing performance issues, consider the following strategies:• Optimize the Table: Before adding a new column, ensure that the table is optimized. Use the OPTIMIZE command to compact small files into larger ones, which can improve performance by reducing the number of files the system needs to manage.• Schema Evolution: Delta Lake supports schema evolution, allowing you to add new columns without rewriting the entire dataset. Use the ALTER TABLE command to add a new column:
 

sql
  ALTER TABLE <table_name> ADD COLUMNS (new_column_name <data_type>);