I have been using SimMetrics to implement the QGramsDistance search in SQL Server. The SimMetrics is used as a SQL CLR assembly. The search results are promising and everything was well, until of late, the database has grown and the number of records have crossed a few hundred thousand with multiple users performing searches. Now, I encounter this error.
Msg 6522, Level 16, State 2, Procedure SchoolNameAutoCompletion, Line 42 A .NET Framework error occurred during execution of user-defined routine or aggregate "QGramsDistance": System.InvalidOperationException: Collection was modified; enumeration operation may not execute. System.InvalidOperationException: at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource) at System.Collections.Generic.List`1.Enumerator.MoveNextRare() at System.Collections.Generic.List`1.Enumerator.MoveNext() at SimMetricsMetricUtilities.QGramsDistance.GetActualSimilarity(Collection`1 firstTokens, Collection`1 secondTokens) at SimMetricsMetricUtilities.QGramsDistance.GetSimilarity(String firstWord, String secondWord) at MyAssembly.DbTextFunctions.StringMetrics.QGramsDistance(SqlString firstWord, SqlString secondWord)
I have tried using the latest version of the SimMetrics in SQL Server 2012 using the .NET framework v4.0.30319 but has not made a difference. It's pretty clear that this error occurs only when more than a single search is performed. Has anyone come across such an issue and have it resolved?