Microsoft Fabric Error:
Fabric Warehouse Query Failure — tempdb Space
What does this error mean?
A query running in Fabric Data Warehouse fails because the internal tempdb system database has run out of space. Tempdb is used for intermediate query results and cannot be configured by users — the solution is to optimize the query to reduce its tempdb consumption.
Common causes
- 1The query performs large intermediate sort, hash join, or aggregation operations that spill to tempdb
- 2Column statistics are missing or stale, causing the query optimizer to choose a plan with excessive tempdb usage
- 3Multiple resource-intensive queries are running concurrently, jointly exhausting tempdb space
- 4Large DML operations (INSERT, UPDATE, DELETE) on tables without up-to-date statistics
How to fix it
- 1Create or update column statistics on all tables involved in the query: CREATE STATISTICS <stat_name> ON <table>(<column>).
- 2After any large DML operation (INSERT/UPDATE/DELETE affecting >10% of rows), run UPDATE STATISTICS <table>.
Beyond the docs
Common practitioner solutions not covered in the official documentation.
- 1Simplify the query: break large queries into smaller steps using CTEs or staging tables to reduce peak intermediate data volume
- 2Avoid SELECT * in large queries — project only the columns actually needed to reduce row width in intermediate results
- 3Monitor concurrently running queries using Warehouse DMVs (sys.dm_exec_requests) and schedule heavy workloads at off-peak times