How Delta UniForm works
Learn how Delta UniForm enables read and write interoperability from Delta tables to Iceberg and Hudi formats.
Delta UniForm (Delta Universal Format) is a unified table format layer built on Delta Lake that enables seamless read and write interoperability from Delta tables to Apache Iceberg and Apache Hudi, without manual conversions or format-specific logic.
💡UniForm was created at DataBricks and is part of the Delta Lake Open Source project.
How does it work
Traditionally, if you want to move data from one format to another, you need to read as source format and write as target format, which generates a copy of data while consuming resources. With Uniform, interoperability is possible as all the open table formats are built on top of Parquet files, the difference is how they store metadata.
💡One data copy with multiple format support through metadata files.
UniForm is part of Delta Lake so it only supports Delta to Iceberg/Hudi conversion. To enable Uniform for Iceberg on a Delta Table:
CREATE TABLE main.default.UniForm_demo_table (msg STRING)
TBLPROPERTIES(’delta.universalFormat.enabledFormats’ = ‘iceberg’);Once the property is enabled, it generates and incrementally maintains the metadata files for the target version.
📖 Recommended Reading: How Delta Lake Works
Since source table is Delta, it supports Delta optimizations which also reflect in the target metadata files to give similar read performance. However, target specific optimizations are not possible today.
Write Flow
User submits a write query with Iceberg enabled through UniForm.
Native Delta Table logs and data are updated. Read detailed Delta write flow here.
UniForm translates logical actions (insert/update/delete/merge) into target format commits.
Target metadata is incrementally & asynchronously updated i.e. Iceberg metadata files. This makes sure Iceberg metadata is always in sync giving a unified view of the same data.
Impact: Slight overhead due to metadata translation which could degrade write performance upto 5%.
Read Flow
Read is same as like reading a native table as shared for Delta Table here.
User submits a query to read from an Iceberg Table.
Query fetches the required metadata, in our case Iceberg from the below options.
Delta → _delta_log/Iceberg → metadata/
Construct the table snapshot and read the Parquet Data files using the native reader. Note: These are the same files that were generated by Delta during write operation.
Results returned via the compute engine to the user.
Impact: The table is read directly using Iceberg metadata so there is no impact on read performance.
Use Case
A simple scenario for using UniForm is when other systems require your Delta table to be accessible in Iceberg or Hudi format. In such cases, UniForm can seamlessly generate the necessary metadata files with almost negligible impact on performance.
Below is the architecture showing where does UniForm fits in the picture.
In the above image, Databricks generates Delta Table with Iceberg enabled through Uniform. Delta is for Databricks and Iceberg is for Snowflake.
💡UniForm will become a critical tool with AWS investing heavily in Iceberg, the need to read Delta Tables as Iceberg will increase rapidly.
Alternative
Apache XTable is another option that supports interoperability across all major table formats, enabling conversions from any source to any target. In contrast, Delta UniForm only supports Delta as the source format.
📖 UniForm initially supported interoperability from Delta to Iceberg. To extend this capability to Hudi, Delta UniForm partnered with XTable.
Conclusion
By bridging the gap between modern lakehouse formats, Delta UniForm simplifies data sharing and format compatibility across platforms, positioning itself as a key enabler of open, multi-engine lakehouse interoperability alongside emerging alternatives like Apache XTable.
References
Open Source Delta UniForm: https://delta.io/blog/unifying-open-table/
Databricks Delta UniForm: https://www.databricks.com/blog/delta-uniform-universal-format-lakehouse-interoperability
AWS Delta to Iceberg through UniForm: https://aws.amazon.com/blogs/big-data/expand-data-access-through-apache-iceberg-using-delta-lake-uniform-on-aws/
Apache XTable overview: https://xtable.apache.org/