Resurrect indexHint function.

[amosbird]

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Changelog category (leave one):

• New Feature

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

Add back indexHint function. This is for #21238 . This reverts #9542 . This fixes #9540 .

Detailed description / Documentation draft:

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[amosbird]

Integration tests (thread) — fail: 1, passed: 1040, error: 24

E           Code: 159. DB::Exception: Received from 172.19.0.6:9000. DB::Exception: Watching task /clickhouse/task_queue/ddl/query-0000000017 is executing longer than distributed_ddl_task_timeout (=180) seconds. There are 1 unfinished hosts (0 of them are currently active), they are going to execute the query in background. Stack trace:

[nikitamikhaylov]

Maybe also add some test case from linked issue?

[azat]

@amosbird but why it returns the first row too for select * from tbl WHERE indexHint(t = 1) order by t with index_granularity=1?

P.S. it worth converting this test to use -- { echo } test hint, see https://github.com/ClickHouse/ClickHouse/blob/master/tests/queries/0_stateless/01564_test_hint_woes.sql for example

[amosbird]

but why it returns the first row too for select * from tbl WHERE indexHint(t = 1) order by t with index_granularity=1

It's how primary index work in clickhouse. The current granule starts with value 1 doesn't mean all values in previous granule < 1

[amosbird]

Maybe also add some test case from linked issue?

Sure. Tests are added.