@Override
public Expression optimize(Session session) {
userConnection = session.createConnection(false);
int len = args.length;
argTypes = new int[len];
for (int i = 0; i < len; i++) {
Expression expr = args[i];
args[i] = expr.optimize(session);
int type = expr.getType();
argTypes[i] = type;
}
try {
Aggregate aggregate = getInstance();
dataType = aggregate.getInternalType(argTypes);
} catch (SQLException e) {
throw DbException.convert(e);
}
return this;
}
@Override
public Value getValue(Session session) {
HashMap<Expression, Object> group = select.getCurrentGroup();
if (group == null) {
throw DbException.get(ErrorCode.INVALID_USE_OF_AGGREGATE_FUNCTION_1, getSQL());
}
try {
Aggregate agg = (Aggregate) group.get(this);
if (agg == null) {
agg = getInstance();
}
Object obj = agg.getResult();
if (obj == null) {
return ValueNull.INSTANCE;
}
return DataType.convertToValue(session, obj, dataType);
} catch (SQLException e) {
throw DbException.convert(e);
}
}
@Override
public void updateAggregate(Session session) {
HashMap<Expression, Object> group = select.getCurrentGroup();
if (group == null) {
// this is a different level (the enclosing query)
return;
}
int groupRowId = select.getCurrentGroupRowId();
if (lastGroupRowId == groupRowId) {
// already visited
return;
}
lastGroupRowId = groupRowId;
Aggregate agg = (Aggregate) group.get(this);
try {
if (agg == null) {
agg = getInstance();
group.put(this, agg);
}
Object[] argValues = new Object[args.length];
Object arg = null;
for (int i = 0, len = args.length; i < len; i++) {
Value v = args[i].getValue(session);
v = v.convertTo(argTypes[i]);
arg = v.getObject();
argValues[i] = arg;
}
if (args.length == 1) {
agg.add(arg);
} else {
agg.add(argValues);
}
} catch (SQLException e) {
throw DbException.convert(e);
}
}
// 调用了两次，一次在optimize，另一次在updateAggregate
private Aggregate getInstance() throws SQLException {
Aggregate agg = userAggregate.getInstance();
agg.init(userConnection);
return agg;
}