[function] isnotnull

[wangsimo0]

StarRocks already have a function named isnull.
https://docs.starrocks.io/en-us/latest/sql-reference/sql-functions/utility-functions/isnull
For easy of use, it's better to have a function that isnotnull.

[qmengss]

Hi, I am interested in this issue, but I didn't find a function name "isnull" in gensrc/script/functions.py.

[LiShuMing]

yep. isnull is implemented by expression, not by built-in function framework. But it's the same principle as the function.

FE will convert the ISNULL to IsNullPredicate:

        if (functionName.equals(FunctionSet.ISNULL)) {
            List<Expr> params = visit(context.expression(), Expr.class);
            if (params.size() != 1) {
                throw new ParsingException(PARSER_ERROR_MSG.wrongNumOfArgs(functionName), pos);
            }
            return new IsNullPredicate(params.get(0), false, pos);
        }

IsNullPredicate will be converted to VectorizedIsNullPredicate in the BE

public class IsNullPredicate extends Predicate {

    static Function isNullFN = new Function(new FunctionName("is_null_pred"),
            new Type[] {Type.INVALID}, Type.BOOLEAN, false);
    static Function isNotNullFN = new Function(new FunctionName("is_not_null_pred"),
            new Type[] {Type.INVALID}, Type.BOOLEAN, false);
    {
        isNullFN.setBinaryType(TFunctionBinaryType.BUILTIN);
        isNotNullFN.setBinaryType(TFunctionBinaryType.BUILTIN);
    }

}

The implements is like this:

class VectorizedIsNullPredicate final : public Predicate {
public:
    DEFINE_CLASS_CONSTRUCT_FN(VectorizedIsNullPredicate);

    StatusOr<ColumnPtr> evaluate_checked(ExprContext* context, Chunk* ptr) override {
        ASSIGN_OR_RETURN(ColumnPtr column, _children[0]->evaluate_checked(context, ptr));

        if (column->only_null()) {
            return ColumnHelper::create_const_column<TYPE_BOOLEAN>(true, column->size());
        }

        if (!column->is_nullable() || !column->has_null()) {
            return ColumnHelper::create_const_column<TYPE_BOOLEAN>(false, column->size());
        }

        auto col = ColumnHelper::as_raw_column<NullableColumn>(column)->null_column();
        return VectorizedStrictUnaryFunction<isNullImpl>::evaluate<TYPE_NULL, TYPE_BOOLEAN>(col);
    }
};

DEFINE_UNARY_FN_WITH_IMPL(isNotNullImpl, v) {
    return v == 0;
}

[leoyy0316]

@kateshaowanjou Can you assign this issue to me？