@Override
public void visit(Function function) {
// all aggregate functions (SUM, AVG, COUNT, MAX, MIN) have only one parameter (Expression)
// although COUNT(*) has no parameters
// EXTRACT_YEAR has one parameter
// if you change this method, NameProjectVisitor.visit(Function) has to be changed as well
ExpressionList params = function.getParameters();
int numParams = 0;
if (params != null) {
params.accept(this);
// in order to determine the size
List<Expression> listParams = params.getExpressions();
numParams = listParams.size();
}
List<ValueExpression> expressions = new ArrayList<ValueExpression>();
for (int i = 0; i < numParams; i++) {
expressions.add(_exprStack.pop());
}
Collections.reverse(expressions); // at the stack top is the lastly added VE
String fnName = function.getName();
if (fnName.equalsIgnoreCase("EXTRACT_YEAR")) {
if (numParams != 1) {
throw new RuntimeException("EXTRACT_YEAR function has exactly one parameter!");
}
ValueExpression expr = expressions.get(0);
ValueExpression ve = new IntegerYearFromDate(expr);
_exprStack.push(ve);
}
}
public void visit(Function function) throws Exception {
if (function.getParameters() == null) return;
for (Expression exp : function.getParameters().getExpressions()) {
exp.accept(this);
}
}