The use of the SQL parser is optional but the SQLParser header is included unconditionally in e.g. the Statement.h header.

This is problematic as SQLParser.h itself includes

but these are only considered if the parser is active

and thus these don't end up getting installed along the other stuff if the parser is disabled. However, as soon as that happens compilation fails as the parser's header includes these non-existent files.

Therefore, I think it would probably make sense to add some conditional including at some point. Most logical to me would seem to guard the includes of SQLParser.h itself.