What is Delta Lake?
Delta Lake is an open-source storage layer that brings reliability and performance to data lakes. Built on top of Parquet, it adds features like ACID transactions, schema enforcement, and efficient data modification. Unlike plain Parquet files, Delta Lake lets you append, update, and delete rows without rewriting the entire dataset, making it a practical choice for data pipelines that handle frequent updates.
Conclusion
Appending data to Parquet files with pandas means loading the entire existing table into memory, merging, and rewriting. As your datasets grow, this becomes a bottleneck. Delta Lake solves this by supporting incremental writes out of the box, so you only write the new data without touching what already exists. With Delta Lake, you can add, remove, or modify columns without the need to recreate the entire table.
My previous tips on pandas alternatives.
If the performance gap between pandas and alternatives like Delta Lake has you rethinking your data stack, you’re not alone. In our deep dive on pandas vs Polars vs DuckDB, we benchmark all three tools on data loading, groupby operations, and query performance to help you pick the right one for your workload.
