Runaway queries
Applies to: ✅ Microsoft Fabric ✅ Azure Data Explorer ✅ Azure Monitor ✅ Microsoft Sentinel
A runaway query is a kind of partial query failure that happens when some internal query limit was exceeded during query execution.
For example, the following error may be reported:
HashJoin operator has exceeded the memory budget during evaluation. Results may be incorrect or incomplete.
There are several possible courses of action.
- Change the query to consume fewer resources. For example, if the error indicates that the query result set is too large, you can:
- Limit the number of records returned by the query by
- Using the take operator
- Adding additional where clauses
- Reduce the number of columns returned by the query by
- Using the project operator
- Using the project-away operator
- Using the project-keep operator
- Use the summarize operator to get aggregated data.
- Limit the number of records returned by the query by
- Increase the relevant query limit temporarily for that query. For more information, see query limits - limit on memory per iterator. This method, however, isn't recommended. The limits exist to protect the cluster and to make sure that a single query doesn't disrupt concurrent queries running on the cluster.
- Increase the relevant query limit temporarily for that query. For more information, see query limits - limit on memory per iterator. This method, however, isn't recommended. The limits exist to protect the Eventhouse and to make sure that a single query doesn't disrupt concurrent queries running on the Eventhouse.