relmodel: Add method sqltype::consistent().

This allows modelling type compatibility beyond equality.

Author: anse1

relmodel.cc

@@ -8,4 +8,9 @@ sqltype * sqltype::get(string n)
     return typemap[n];
   else
     return typemap[n] = new sqltype(n);
-};
+}
+
+bool sqltype::consistent(struct sqltype *rvalue)
+{
+  return this == rvalue;
+}

relmodel.hh

@@ -21,6 +21,7 @@ struct sqltype {
   static map<string, struct sqltype*> typemap;
   static struct sqltype *get(string s);
   sqltype(string n) : name(n) { }
+  virtual bool consistent(struct sqltype *rvalue);
 };
 
 struct column {