I would like to ask, would you see this solution in general as fine, or is there any better way to achieve this? I particularly dislike the part when we are trying matching return string on "cached plan must not change result type" as error messages might change (e.g. situations using different locales), is there any way how to get around this e.g. with enumerator?
Source code says that the errcode being returned is "Feature Not Supported" which seems unreasonably broad, I'd probably stick with message text parsing. If you have locale concerns you could just check for one of the 11 different translations that are presently provided. Or combine them, checking for the error code value first (which probably would be rare enough in production code to be usable) then fall back to the description.
