Compiler warns about empty format string when SET_DBASE is empty

[Eyal Rozenberg]

SET_DBASE is the format string for the command to set the active database, used in qgen. Now, for some DBMSes, no such command exists, because a connection is associated with a single database from the get-go (e.g. MonetDB, VectorWise). The thing is, in qgen.c we have the line:

fprintf(ofp, SET_DBASE, db_name);

and this triggers a compiler warning when SET_DBASE is empty - empty format string with more than 0 extra arguments to fprintf(). Let's avoid this warning.