@tbonfort, @rouault, @dmorissette, I'd like to suggest a breaking change for 7.0 as a result of the RFC 91 work. Presently if you use a database driver and it sees filter->string set it takes that as SQL. From setting via a mapfile the expression is of type MS_STRING. For RFC 91 I added an explicit native_string structure member and changed db drivers to only use that if not NULL. Works ok...

However, digging into the SLD and WMS time code I found that native expressions were being created as type MS_EXPRESSION (e.g. MapServer expression syntax ('[column]' eq 'foo')). That was a problem since those were the types of expressions we want to be able to translate to native SQL. Ugh... I had to force the filter type to MS_STRING in those instances.

It would be nice to be more explicit. OGR uses a "WHERE " qualifier and I think it would make sense to do the same universally. That what the load expression function can strip off the WHERE, set native_string and a specific type (MS_NATIVE_EXPRESSION). It'll be more convenient for MapScript users.

This is a relatively simple change but it can break some stuff: mapfiles that use database drivers and FILTERs (there's little reason to do so) and MapScript scripts that use setFilter() with database drivers. I think those should be relatively limited.

I know the RFC has been a pain in the ass but now is the time...

Steve