Add loop() table function

[sarielwxm]

Fixes #52765

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

Added a new table function loop to support returning query results in an infinite loop.

Documentation entry for user-facing changes

• Documentation is written (mandatory for new features)

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[robot-ch-test-poll2]

This is an automated comment for commit 0f952cc with description of existing statuses. It's updated for the latest CI running

❌ Click here to open a full report in a separate page

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Check name	Description	Status
AST fuzzer	Runs randomly generated queries to catch program errors. The build type is optionally given in parenthesis. If it fails, ask a maintainer for help	✅ success
ClickBench	Runs [ClickBench](https://github.com/ClickHouse/ClickBench/) with instant-attach table	✅ success
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[divanik]

Hi, @sarielwxm. Thank you for your contribution to Clickhouse! I will be glad to review your PR. Firstly, I'd like to ask you to add the example output after execution of this table function that demonstrates its typical behaviour to the documentation. Secondly, could you please write a fast test that checks desired behaviour of the function? After these steps I will be able to continue the reviewing process

[sarielwxm]

Hi, @sarielwxm. Thank you for your contribution to Clickhouse! I will be glad to review your PR. Firstly, I'd like to ask you to add the example output after execution of this table function that demonstrates its typical behaviour to the documentation. Secondly, could you please write a fast test that checks desired behaviour of the function? After these steps I will be able to continue the reviewing process

Sure. I have already tested it locally. But I have a problem because this table function implements an infinite loop over the query results and it seems difficult to represent the example output. Could you please give me some suggestions? Much appreciated!

[divanik]

Sure. I have already tested it locally. But I have a problem because this table function implements an infinite loop over the query results and it seems difficult to represent the example output. Could you please give me some suggestions? Much appreciated!

Could you use LIMIT operator to bound the output of the loop function?

[sarielwxm]

Could you use LIMIT operator to bound the output of the loop function?

Got it. It's useful.

[divanik]

❌ Click here to open a full report on a separate page - you can find a report, why some CI tests failed. Tests that you added shouldn't be flaky. But there are some flaky tests in our repository (tests that fail in master CI, and they can fail in your PR as well). You can find them at https://aretestsgreenyet.com. If you see that a test fail both in your PR and master, you can forget about it more or less. But in our case, the new test is flaky that's why it should be fixed before PR merge. Everything else looks good to me

[divanik]

There is need to fix the flaky test

[divanik]

LGTM. There are some issues with CI, I will try to resolve them by myself