Add mode fot topK/topKWeighed function to also include count/error statistics

[UnamedRus]

Changelog category (leave one):

• New Feature

Fix for #42029

Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):

topK/topKWeighed support mode, which return count of values and it's error.

Documentation entry for user-facing changes

• Documentation is written (mandatory for new features)

Information about CI checks: https://clickhouse.com/docs/en/development/continuous-integration/

SELECT
    topK(10, 900, 'include_statistics')(number % 3000) AS top,
    top.1 AS key,
    tupleElement(top, 'count') AS cnt_arr,
    tupleElement(top, 'error') AS err_arr
FROM numbers_mt(10000000)
FORMAT Vertical

Query id: b6d68539-5cb1-4fa5-812c-bc331c7c61dc

Row 1:
──────
top:     [(581,3334,0),(160,3334,0),(666,3334,0),(175,3334,0),(305,3334,0),(378,3334,0),(124,3334,0),(794,3334,0),(833,3334,0),(688,3334,0)]
key:     [581,160,666,175,305,378,124,794,833,688]
cnt_arr: [3334,3334,3334,3334,3334,3334,3334,3334,3334,3334]
err_arr: [0,0,0,0,0,0,0,0,0,0]

SELECT
    topK(10, 900, 'include_statistics')((number % 300, CAST(number % 30, 'DateTime'), toString(number % 2))) AS top,
    top.1 AS key,
    tupleElement(top, 'count') AS cnt_arr,
    tupleElement(top, 'error') AS err_arr
FROM numbers_mt(10000000)
FORMAT Vertical

Query id: 1f4e1f10-fde7-4608-aed3-3bfa8187f8aa

Row 1:
──────
top:     [((5,'1970-01-01 00:00:05','1'),33334,0),((27,'1970-01-01 00:00:27','1'),33334,0),((85,'1970-01-01 00:00:25','1'),33334,0),((41,'1970-01-01 00:00:11','1'),33334,0),((20,'1970-01-01 00:00:20','0'),33334,0),((50,'1970-01-01 00:00:20','0'),33334,0),((80,'1970-01-01 00:00:20','0'),33334,0),((52,'1970-01-01 00:00:22','0'),33334,0),((2,'1970-01-01 00:00:02','0'),33334,0),((62,'1970-01-01 00:00:02','0'),33334,0)]
key:     [(5,'1970-01-01 00:00:05','1'),(27,'1970-01-01 00:00:27','1'),(85,'1970-01-01 00:00:25','1'),(41,'1970-01-01 00:00:11','1'),(20,'1970-01-01 00:00:20','0'),(50,'1970-01-01 00:00:20','0'),(80,'1970-01-01 00:00:20','0'),(52,'1970-01-01 00:00:22','0'),(2,'1970-01-01 00:00:02','0'),(62,'1970-01-01 00:00:02','0')]
cnt_arr: [33334,33334,33334,33334,33334,33334,33334,33334,33334,33334]
err_arr: [0,0,0,0,0,0,0,0,0,0]

Parameter naming & handling can be better, i guess.

[robot-ch-test-poll4]

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[yakov-olkhovskiy]

overall looks good but it would be nice to add some tests

[UnamedRus]

overall looks good but it would be nice to add some tests

It was more like POC example, will work on tests, if it's OK change.
I'm a little dislike, that change of parameter lead to change signature of function, but don't see any better way. (ie not use parameter for that)

Introduction of new aggregate function, like TopKWeighedCount, unfortunately will make people expect that they are different functions with different state and not same.

Anyway, it looks like, we better add

APPROX_TOP_K (TopK) and APPROX_TOP_SUM (TopKWeighed) aliases, because they are much more common in other dbms. Unfortunately, they don't have concept of parameters, so everything is being passed as arguments, so different signature, but ClickHouse way is slightly better to my taste.
Plus,

Third parameter value is slightly different, in ClickHouse its does mean load_factor, but in other dbms it does mean total amount of tracked elements. for ClickHouse it will be ( load_factor*N )

#42029 (comment)

[yakov-olkhovskiy]

@UnamedRus could you please merge master again?