/** Adds an expression and returns a reference name. */
public String addExpr(Expr expr) throws PlanningException {
if (idToExprBiMap.inverse().containsKey(expr)) {
int refId = idToExprBiMap.inverse().get(expr);
return idToNamesMap.get(refId).get(0);
}
String generatedName = plan.generateUniqueColumnName(expr);
return addExpr(expr, generatedName);
}
