ISSUES-2553 add offset parameter to numbers

[zhang2014]

#2535
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[alexey-milovidov]

You didn't provide any motivation for this change.
So I have to guess, is it any useful.

At first glance, it seems completely useless,
because the user can always write

SELECT number + 10 FROM numbers(123)

instead of

SELECT number FROM numbers(10, 123)

and proposed change will only make query language more heavy.

It's also non obvious (without reading the docs), what does numbers(n, m) means:

• offset and limit;
• range begin and end, including end;
• range begin and end, not including end.

But finally I found at least some possible motivation for your change (but I leave it for you).

[zhang2014]

Sorry, I didn't introduce motivation.

At first glance, it seems completely useless,
because the user can always write
SELECT number + 10 FROM numbers(123)
instead of
SELECT number FROM numbers(10, 123)
and proposed change will only make query language more heavy.

You are right, but

• it's always more efficient
• SELECT number + 10 AS a, number + 10 AS b ... number + 10 AS n ... is complicated.
• numbers(10, 123) can always be rewritten as SELECT number FROM system.numbers LIMIT 10,123
• Maybe we can also support negative numbers : )

[filimonov]

1. I doubt tgat performance of numbers table can be a bottleneck in some real scenarios.
2. you can simplyfy such a selects using WITH clause like

with number + 10 as number2
select number2 as a, number2 as b ...

3. may be it would be better to introduce range/enumerate table function which will support all data types customizable init value and customizable increment step? Like classic for keyword in programming languages? For example select mondays from enumerate(toDate('2018-08-25'), x -> x <= toDate('2018-12-31'), x -> x + INTERVAL 7 DAYS)

[zhang2014]

I doubt tgat performance of numbers table can be a bottleneck in some real scenarios.

Yes, if you use LIMIT m, n you will have unnecessary wait offset, and if you use number + m ... LIMIT n you will have unnecessary operations, like '+'

you can simplyfy such a selects using WITH clause like

That's great

may be it would be better to introduce range/enumerate table function which will support all data types customizable init value and customizable increment step? Like classic for keyword in programming languages? For example select mondays from enumerate(toDate('2018-08-25'), x -> x <= toDate('2018-12-31'), x -> x + INTERVAL 7 DAYS)

Good idea, but the implementation is complicated, but I'll try : )