/** 将Avg函数展开为sum/count */
private void expendAvgFunction(IDataNodeExecutor sub) {
if (sub instanceof IQuery || sub instanceof IJoin) {
List<ISelectable> add = new ArrayList();
List<ISelectable> remove = new ArrayList();
for (Object sel : ((IQueryTree) sub).getColumns()) {
ISelectable s = (ISelectable) sel;
if (s instanceof IFunction) {
if (s.getColumnName().startsWith("AVG(")) {
IFunction sum = (IFunction) s.copy();
sum.setExtraFunction(null);
sum.setFunctionName("SUM");
sum.setColumnName(s.getColumnName().replace("AVG(", "SUM("));
if (sum.getAlias() != null) {
sum.setAlias(sum.getAlias() + "1"); // 加个后缀1
}
IFunction count = (IFunction) s.copy();
count.setExtraFunction(null);
count.setFunctionName("COUNT");
count.setColumnName(s.getColumnName().replace("AVG(", "COUNT("));
if (count.getAlias() != null) {
count.setAlias(count.getAlias() + "2"); // 加个后缀2
}
add.add(count);
add.add(sum);
remove.add(s);
} else {
// 删除底下AVG的相关函数，比如 1 + AVG(ID)
// 目前这个只能上层来进行计算
// 可能的风险：还未支持的Function计算
if (FunctionType.Scalar.equals(((IFunction) s).getFunctionType())
&& hasArgsAvgFunction((IFunction) s)) {
remove.add(s);
}
}
}
}
if (!remove.isEmpty()) {
((IQueryTree) sub).getColumns().removeAll(remove);
((IQueryTree) sub).getColumns().addAll(add);
}
}
}
