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.
Read more: Microsoft Learn
In the Ultra Transcenders books
Each book explains readHeavyForPBI in context, with comparison tables and the common traps.
Terms in this definition
- 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.
- 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.
- CRUD
Shorthand for create, read, update and delete, the four basic things you do with data. Data-plane roles in Azure Cosmos DB, for instance, authorise those operations on items.
- V-Order
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 ... VORDERapplies it to files already written. - Optimized writes
Enabled with
delta.autoOptimize.optimizeWrite, this Delta option shuffles data ahead of the write so that fewer but larger files result. Partitioned tables benefit the most, andMERGE,UPDATEandDELETEuse it by default. - 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.