🏭🗒️Microsoft Fabric: V-Order [Notes]

Disclaimer: This is work in progress intended to consolidate information from various sources for learning purposes. For the latest information please consult the documentation (see the links below)! 

Last updated: 17-Mar-2024

[Microsoft Fabric] V-Order

• {def} write time optimization to the parquet file format that enables fast reads under the MF compute engine [2]
• all parquet engines can read the files as regular parquet files [2]
• results in a smaller and therefore faster files to read [5]
• {benefit} improves read performance 
• {benefit} decreases storage requirements
• {benefit} optimizes resources' usage
• reduces the compute resources required for reading data
• e.g. network bandwidth, disk I/O, CPU usage
• still conforms to the open-source Parquet file format [5]
• they can be read by non-Fabric tools [5]
• delta tables created and loaded by Fabric items automatically apply V-Order
• e.g. data pipelines, dataflows, notebooks [5]
• delta tables and its features are orthogonal to V-Order [2]
•  e.g. Z-Order, compaction, vacuum, time travel
• table properties and optimization commands can be used to control the v-order of the partitions [2]
• compatible with Z-Order [2]
• not all files have this optimization applied [5]
• e.g. Parquet files uploaded to a Fabric lakehouse, or that are referenced by a shortcut 
• the files can still be read, the read performance likely won't be as fast as an equivalent Parquet file that's had V-Order applied [5]
• required by certain features
• [hash encoding] to assign a numeric identifier to each unique value contained in the column [5]
• {command} OPTIMIZE 
• optimizes a Delta table to coalesce smaller files into larger ones [5]
• can apply V-Order to compact and rewrite the Parquet files [5]
• [warehouse] 
• works by applying certain operations on Parquet files
• special sorting
• row group distribution
• dictionary encoding
• compression 
• enabled by default
•  ⇒ compute engines require less network, disk, and CPU resources to read data from storage [1]
• provides cost efficiency and performance [1]
• the effect of V-Order on performance can vary depending on tables' schemas, data volumes, query, and ingestion patterns [1]
• fully-compliant to the open-source parquet format [1]
• ⇐ all parquet engines can read it as regular parquet files [1]
• required by certain features
• [Direct Lake mode] depends on V-Order
• {operation} disable V-Order
• causes any new Parquet files produced by the warehouse engine to be created without V-Order optimization [3]
• irreversible operation
•  once disabled, it cannot be enabled again [3]
• {scenario} write-intensive warehouses
• warehouses dedicated to staging data as part of a data ingestion process [1]
• {warning} consider the effect of V-Order on performance before deciding to disable it [1]
• {recommendation} test how V-Order affects the performance of data ingestion and queries before deciding to disable it [1]
• via ALTER DATABASE CURRENT SET VORDER = OFF; [3]
  
• {operation} check current status
• via  SELECT name, is_vorder_enabled FROM sys.databases; [post]
• {feature} [lakehouse] Load to Table
• allows to load a single file or a folder of files to a table [6]
• tables are always loaded using the Delta Lake table format with V-Order optimization enabled [6]
• [Direct Lake semantic model] 
• data is prepared for fast loading into memory [5]
• makes less demands on capacity resources [5]
• results in faster query performance [5]
• because less memory needs to be scanned [5]

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References:
[1] Microsoft Learn (2024) Fabric: Understand V-Order for Microsoft Fabric Warehouse [link]
[2] Microsoft Learn (2024) Delta Lake table optimization and V-Order [link]
[3] Microsoft Learn (2024) Disable V-Order on Warehouse in Microsoft Fabric [link]
[4] Miles Cole (2024) To V-Order or Not: Making the Case for Selective Use of V-Order in Fabric Spark [link]
[5] Microsoft Learn (2024) Understand storage for Direct Lake semantic models [link]

[6] Microsoft Learn (2025] Fabric: Load to Delta Lake table [link]

Resources:
[R1] Serverless.SQL (2024) Performance Analysis of V-Ordering in Fabric Warehouse: On or Off?, by Andy Cutler [link]
[R2] Redgate (2023 Microsoft Fabric: Checking and Fixing Tables V-Order Optimization, by Dennes Torres [link]
[R3] Sandeep Pawar (2023) Checking If Delta Table in Fabric is V-order Optimized [link]

[R4] Microsoft Learn (2025) Fabric: What's new in Microsoft Fabric? [link]

Acronyms:
MF - Microsoft Fabric