I understand the difficulties of library development. I am just trying to be helpful and describe our use case in as much details as possible.

Incidentally I've also stumbled upon bug HHH-7473 Closed , where StandardAnsiSqlAggregationFunctions.SumFunction class does a similar type resolution. We have another custom type (PrimaryKeyType) which is affected by this bug, although summing a column of this type is clearly a bug on our side. However I've noticed that our IBMBigDecimalType custom type only passes this resolution because it maps to java.sql.Types.NUMERIC jdbc type, which is ignored by the resolution method. I was wondering if on the general level the pluggable type resolution strategy shouldn't handle this case too.