An optimisation Fabric applies to Parquet files as they are written, covering sorting, row-group layout, encoding and compression, so reads (above all Direct Lake) are quicker at some cost to writes. New workspaces have it switched off, and OPTIMIZE ... VORDER applies it to files already written.
Read more: Microsoft Learn
In the Ultra Transcenders books
Each book explains V-Order in context, with comparison tables and the common traps.
Terms in this definition
- Parquet
Columnar file format, open source and aimed at analytics. Event Hubs Capture cannot produce it natively.
- ENCODING
A COPY INTO option for CSV sources that states whether the files use UTF8, the default, or UTF16 character encoding.
- ALL
A DAX function that ignores any filters and gives back every row of a table or every value of the named columns. Used within CALCULATE, it works as a modifier that clears filters, although REMOVEFILTERS states that intent more clearly where it is available.
- Direct Lake
Mode for Fabric semantic models that loads Delta or Parquet files from OneLake straight into VertiPaq, giving almost import-level performance without duplicating data.
- OPTIMIZE
Bin-packs small files into larger ones, or reclusters liquid-clustered tables, when you run this SQL command; for Unity Catalog managed tables, predictive optimization takes care of it automatically.
Related terms
- Lakehouse maintenance activity
Preview pipeline step for scheduled upkeep of lakehouse Delta tables, running OPTIMIZE (optionally with V-Order) followed by VACUUM.
- Lakehouse table maintenance
Running OPTIMIZE (V-Order optional) and VACUUM against a Delta table with no Spark coding, from the Maintenance dialog in lakehouse explorer. The same job can also be triggered by a pipeline activity or through a REST API.
- readHeavyForPBI
A Spark resource profile in Fabric meant for tables that Direct Lake reports will read heavily; it enables V-Order and 1 GB optimize write bins. Workspaces created today use writeHeavy until changed.
- Resource profile
A ready-made bundle of Delta Lake and Spark settings tuned to a kind of workload, chosen through spark.fabric.resourceProfile. The options are writeHeavy (V-Order off, and what new workspaces get by default), readHeavyForSpark, readHeavyForPBI (V-Order on) and custom.
- writeHeavy
Newly created Fabric workspaces default to this Spark resource profile, controlled by
spark.fabric.resourceProfile. Built for ETL and ingestion, it leaves V-Order switched off; reading suits readHeavyForSpark or readHeavyForPBI better. - Z-Order
Clusters similar values into shared files, via
OPTIMIZE ... ZORDER BY (col)on Delta Lake, so selective filters skip more data. Works alongside V-Order.