Assume that you use Microsoft SQL Server 2012 or SQL Server 2014. When you try to add columns with variable data type online in a temp table, and the columns have a default constraint, a memory leak occurs in USERSTORE_SCHEMAMGR. Additionally, the memory leak may cause the resource monitor to spin, and this could lead to CPU spikes.
Cumulative Update information
The issue was first fixed in the following cumulative update of SQL Server.
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:
Microsoft SQL Server 2012 Service Pack 2, Microsoft SQL Server 2014 Enterprise, Microsoft SQL Server 2014 Developer, Microsoft SQL Server 2014 Standard, Microsoft SQL Server 2014 Web, Microsoft SQL Server 2014 Service Pack 1