Unary operators are supported now

In addition to some over-range functions a bunch of simple functions has been added here: vector(), scalar(), almost all date/time functions (day_of_week(), etc.), almost all math function (abs(), sin(), pi(), etc.).

Interesting why do we need to evaluate constant arguments separately? We will have 2 different pathes for evaluating constant expressions then.

Why do unary operators have a different implementation? We can treat them as simple math functions similarly how ClickHouse does it with negate.

Unary operators in PromQL can be applied to scalars, e.g.

-5
-time()

or instant vectors, e.g.

-vector(1)
-up

And simple math functions can be applied to instant vectors only, so for example sin(vector(1)) works whereas sin(1) doesn't work.

Also unary operator as a different type of node in PrometheusQueryTree makes some code easier, for example when we transform it to string we need to consider precedences of operators.

Do we really need CONST_SCALAR and a SINGLE_SCALAR? Maybe we can only leave the latter one?

CONST_SCALAR is a kind of optimization.

For example, promql query 5 is currently translated to

SELECT toDateTime64(<current_timestamp>, 3) AS timestamp, toFloat64(5.) AS value

and if we get rid of CONST_SCALAR the same promql query will be translated to

WITH
    prometheus_query_step_1 AS (
        SELECT toFloat64(5.) AS value
    ),
SELECT toDateTime64(<current_time>, 3) AS timestamp, toFloat64(value) AS value FROM prometheus_query_step_1

Perhaps we can keep CONST_SCALAR but use it for scalar literals only, like 5 or -5 and not for results of math functions like abs(vector(-5)) - in order to have only one path of evaluation.

#98235