A Spark setting in Fabric that chooses the target file size for each Delta table based on how big the table is, starting at 128 MB for small tables and rising towards 1 GB for very large ones, and reconsiders the choice every time OPTIMIZE runs. It is enabled by default in Runtime 2.0 and removes the need to tune the older delta.targetFileSize property by hand.
Read more: Microsoft Learn
In the Ultra Transcenders books
Each book explains Adaptive target file size in context, with comparison tables and the common traps.
Terms in this definition
- Event
Table in Log Analytics where entries from Windows event logs are kept.
- 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.
- Agents (classic) API
First-generation Foundry Agent Service API, based on threads, messages and runs. It is deprecated, replaced by conversations and responses, and retires on 31 March 2027.
- Runtime 2.0
The Fabric Spark runtime, now generally available and the recommended choice for production, built on Apache Spark 4.1 with Delta Lake 4.2, Python 3.13, Scala 2.13 and Java 21. Its predecessor, Runtime 1.3 on Spark 3.5, reached end of support on 30 September 2026 and moved into Long Term Support from 1 October 2026 until March 2027.
- property
In VCF Operations, an attribute describing how an object is configured, such as its vCPU count. Unlike a metric, it captures state rather than performance over time, and it can feed symptom definitions, views, dashboards and reports.