FIX: Query runs slowly when SQL Server uses hash aggregate in the query plan
Your query may run slowly if the following conditions are true:
- The query uses aggregates such as group by.
- SQL Server uses hash aggregate in the query plan.
- The estimated number of distinct values is much lower than the actual number of distinct values for the aggregate.
This issue occurs because SQL Server underestimates the amount of memory grant needed. This results in intermiedate results spilling to tempdb.
The issue was first fixed in the following cumulative update of SQL Server: Note You have to enable trace flag 9410 to activate this fix.
Recommendation: Install the latest cumulative update for SQL Server
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. We recommend that you download and install the latest cumulative updates for SQL Server:
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Article ID: 3167159 - Last Review: 09/22/2016 03:59:00 - Revision: 3.0
Microsoft SQL Server 2014 Service Pack 1, Microsoft SQL Server 2016 Developer, Microsoft SQL Server 2016 Enterprise, Microsoft SQL Server 2016 Enterprise Core, Microsoft SQL Server 2016 Standard
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