This was already "broken" when you found it, but...
The meaning of "const" for non-pointers like "const voltdb::ValueType columnType = ..." and "const bool isInlined = ..." is "I do not intend to change these local variables (or function input arguments) from their initial values". 
That can help make a variable's purpose clear in a long, complicated function with lots of variables, some of them changing, some of them fixed.
I don't see the benefit in a short simple function where it's perfectly clear what is happening to the variable so "const " there is just a little more noise that distracts from the IMPORTANT use of const with pointers to mean "I do not use/need write access to this object".