iframe-proxy

arujbansal · 2026-03-29T16:43:07Z

Allow a trailing comma in the WITH clause before SELECT queries, e.g. WITH 1 AS a, 2 AS b, SELECT a + b.

The implementation adds an allow_trailing_separator parameter to ParserList and its parseUtil helper, which when enabled keeps the parser position past the trailing comma instead of backtracking.

This resolves #90780.

Changelog category:

Improvement

Changelog entry:

You can now have a trailing comma in the WITH clause before a SELECT query.

Documentation entry for user-facing changes

Documentation is written (mandatory for new features)

Version info

Merged into: 26.4.1.852

arujbansal · 2026-03-29T17:00:17Z

alexey-milovidov

The implementation LGTM, thank you!

clickhouse-gh · 2026-03-29T20:19:32Z

Workflow [PR], commit [1310604]

Summary: ✅

AI Review

Summary

This PR adds support for a trailing comma in WITH before SELECT (for both scalar expressions and CTE forms), wires it through ParserList via an explicit allow_trailing_separator flag, and adds parser tests plus documentation. I reviewed parser behavior, call-site impact, and tests; I did not find any high-confidence correctness, safety, concurrency, or performance issues that require changes.

Missing context

⚠️ No CI results/log links were provided in the review request, so this review is based on code and tests in the diff.

ClickHouse Rules

Item	Status	Notes
Deletion logging	➖
Serialization versioning	➖
Core-area scrutiny	✅
No test removal	✅
Experimental gate	➖
No magic constants	✅
Backward compatibility	✅
`SettingsChangesHistory.cpp`	➖
PR metadata quality	✅
Safe rollout	✅
Compilation time	✅
No large/binary files	✅

Final Verdict

Status: ✅ Approve

alexey-milovidov · 2026-03-30T21:01:21Z

This PR is approved.

arujbansal · 2026-03-30T21:38:11Z

Sounds good.

I’m not sure where else to ask this, so I’ll ask here. After going through the contribution workflow and contributing my first feature, I’d like to continue contributing to ClickHouse. Do you have any recommendations for tasks that would take roughly a few weeks to a month? I’d be interested in either implementing a standalone feature or working on existing ClickHouse internals.

arujbansal · 2026-03-30T23:01:14Z

What do I do about these unrelated failures? I also had unrelated failures earlier so I merged with master and re-ran tests. Is it still possible to merge or does it have to be clean?

alexey-milovidov · 2026-03-30T23:33:26Z

We are in the process of enabling extra fuzzing:

#97568
#98138
#100439
#100490
#101274

That's why there are many unrelated failures.
But these failures are genuine, and we have to fix them.
We are enabling this new combination of fuzzer in steps.

So far, no additional actions are needed; just hold.

alexey-milovidov · 2026-03-30T23:37:31Z

After going through the contribution workflow and contributing my first feature, I’d like to continue contributing to ClickHouse.

This is amazing! There are many tasks under the "warmup task" label. For example, this one:
#59617

The idea is to make the url table function and engine work with various protocols, including file:// and s3://. The function will dispatch itself to the corresponding implementations. There are tricky details that have to be handled carefully. For example, many parameters for the s3 table function will have to be exposed as settings. But the initial implementation will be very simple - just to look at the protocol and dispatch to other table functions accordingly.

alexey-milovidov · 2026-03-30T23:41:06Z

Also to clarify, why this task is needed.

Look at how DatabaseFilesystem and DatabaseOverlay are used in clickhouse-local. It allows to use local files, e.g., SELECT * FROM 'data.csv' along with tables. We will implement DatabaseURL similar to DatabaseFilesystem but it will support both URLs and files. So you can write SELECT * FROM 'data.csv' (using url_base), SELECT * FROM 'https://example.com/data.csv', SELECT * FROM 's3://mybucket/data.csv', etc.

arujbansal · 2026-03-31T00:54:48Z

Thanks! #59617 does look like a good next task. I will work on that.

alexey-milovidov · 2026-04-07T00:27:53Z

The Stress test (arm_msan) failure is fixed by #101239, which should be merged first. After it is merged, please update the branch to include the fix.

alexey-milovidov · 2026-04-08T21:05:31Z

The flaky test failures in this PR (01605_drop_settings_profile_while_assigned, 01418_custom_settings, 02015_async_inserts_4) are caused by non-unique access entity names and will be resolved by #102131.

clickhouse-gh · 2026-04-12T15:18:31Z

LLVM Coverage Report

Metric	Baseline	Current	Δ
Lines	84.00%	84.10%	+0.10%
Functions	90.80%	90.90%	+0.10%
Branches	76.50%	76.60%	+0.10%

Changed lines: 97.78% (44/45) | lost baseline coverage: 4 line(s) · Uncovered code

Full report · Diff report

arujbansal · 2026-04-12T17:34:02Z

Split flaky check and targeted check into separate roles: Flaky check — runs only new/modified tests from the PR with thread fuzzer enabled. Tests run in parallel with themselves (shared queue) to ensure new tests are parallel-safe under randomized thread ordering. Targeted check — runs previously failed and coverage-relevant tests with per-worker partitioning (--no-self-parallel) so the same test never runs concurrently on multiple workers, avoiding conflicts on shared resources (hardcoded users, roles, settings profiles, etc.). Both use --test-runs 50. Changes: - Add --no-self-parallel flag to clickhouse-test: partitions tests by name hash so all copies go to the same worker - Flaky check: only changed tests, thread fuzzer, shared queue - Targeted check: relevant tests, no thread fuzzer, per-worker queues, 50 runs, single clickhouse-test invocation - Restore original thread fuzzer parameters (reverts reductions from 06c945a and 9790435) - Add amd_binary to flaky check, use AMD_LARGE for targeted debug - Targeted check uses --flaky-check --no-self-parallel PRs affected by tests running in parallel with themselves: #102015 #101093 #99653 #101503 #101108 #101884 #100746 #101447 #100941 #101099 #100203 #96130 #102038

Split flaky check and targeted check into separate roles: Flaky check — runs only new/modified tests from the PR with thread fuzzer enabled. Tests can run in parallel with themselves (shared queue) to ensure new tests are parallel-safe. Targeted check — runs previously failed and coverage-relevant tests with per-worker partitioning (--no-self-parallel) so the same test never runs concurrently on multiple workers, avoiding conflicts on shared resources (hardcoded users, roles, settings profiles, etc.). Both use --test-runs 50. Changes: - Add --no-self-parallel flag to clickhouse-test: partitions tests by name hash so all copies go to the same worker - Flaky check: only changed tests, thread fuzzer, shared queue - Targeted check: relevant tests, no thread fuzzer, per-worker partitioning, 50 runs, single clickhouse-test invocation - Restore original thread fuzzer parameters - Change targeted check to arm_asan_ubsan on ARM_LARGE PRs affected by tests running in parallel with themselves: #102015 #101093 #99653 #101503 #101108 #101884 #100746 #101447 #100941 #101099 #100203 #96130

arujbansal added 3 commits March 29, 2026 12:42

Allow trailing comma in WITH clause

e12aa99

Add documentation for trailing comma in WITH clause

c93f563

Cover more test cases for trailing comma in WITH clause

15e60c1

arujbansal marked this pull request as ready for review March 29, 2026 16:59

Add missing change from initial commit

2ac9a70

arujbansal changed the title ~~Allow trailing comma in WITH clause~~ Support for trailing comma in WITH before SELECT Mar 29, 2026

alexey-milovidov reviewed Mar 29, 2026

View reviewed changes

Comment thread docs/en/sql-reference/statements/select/with.md

alexey-milovidov approved these changes Mar 29, 2026

View reviewed changes

alexey-milovidov self-assigned this Mar 29, 2026

alexey-milovidov added the can be tested Allows running workflows for external contributors label Mar 29, 2026

clickhouse-gh Bot added the pr-improvement Pull request with some product improvements label Mar 29, 2026

arujbansal added 7 commits March 29, 2026 16:24

Remove trailing whitespaces

c453f85

Update test

c8c0f0c

Scope test settings to individual queries

f38dd4a

Merge upstream master

7da73a5

Rename test to 04068 to avoid number collision

ed5a3e6

Merge upstream/master

3023657

Rename test to 04070 to avoid number collision

d360704

groeneai mentioned this pull request Apr 1, 2026

Fix flaky test 02030_function_mapContainsKeyLike #101538

Merged

Merge branch 'master' into with-trailing-comma

b71c8c7

Trigger CI

cdeb1e8

arujbansal and others added 2 commits April 10, 2026 10:48

Merge remote-tracking branch 'upstream/master' into with-trailing-comma

ae606c2

Merge branch 'master' into with-trailing-comma

1310604

alexey-milovidov added this pull request to the merge queue Apr 12, 2026

Merged via the queue into ClickHouse:master with commit 196fd77 Apr 12, 2026
164 checks passed

robot-ch-test-poll added the pr-synced-to-cloud The PR is synced to the cloud repo label Apr 12, 2026

groeneai mentioned this pull request Apr 23, 2026

Fix BSONEachRow rollback crash on malformed nullable array elements #103418

Merged

1 task

robot-clickhouse-ci-1 mentioned this pull request Jun 27, 2026

Support for trailing comma in WITH before SELECT #90780

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Changelog category:

Changelog entry:

Documentation entry for user-facing changes

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arujbansal commented Mar 29, 2026 •

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