Add virtual column _headers for url table engine

[ucasfl]

Changelog category (leave one):

• New Feature

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

Add virtual column _headers for url table engine. Closes #65026.

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/

CI Settings (Only check the boxes if you know what you are doing):

• Allow: All Required Checks
• Allow: Stateless tests
• Allow: Stateful tests
• Allow: Integration Tests
• Allow: Performance tests
• Allow: All Builds
• Allow: batch 1, 2 for multi-batch jobs
• Allow: batch 3, 4, 5, 6 for multi-batch jobs

---

• Exclude: Style check
• Exclude: Fast test
• Exclude: All with ASAN
• Exclude: All with TSAN, MSAN, UBSAN, Coverage
• Exclude: All with aarch64, release, debug

---

• Run only fuzzers related jobs (libFuzzer fuzzers, AST fuzzers, etc.)
• Exclude: AST fuzzers

---

• Do not test
• Woolen Wolfdog
• Upload binaries for special builds
• Disable merge-commit
• Disable CI cache

[robot-ch-test-poll2]

This is an automated comment for commit e7d1757 with description of existing statuses. It's updated for the latest CI running

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

Check name	Description	Status
Performance Comparison	Measure changes in query performance. The performance test report is described in detail here. In square brackets are the optional part/total tests	❌ failure

Successful checks

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
Builds	There's no description for the check yet, please add it to tests/ci/ci_config.py:CHECK_DESCRIPTIONS	✅ success
ClickBench	Runs [ClickBench](https://github.com/ClickHouse/ClickBench/) with instant-attach table	✅ success
Compatibility check	Checks that clickhouse binary runs on distributions with old libc versions. If it fails, ask a maintainer for help	✅ success
Docker keeper image	The check to build and optionally push the mentioned image to docker hub	✅ success
Docker server image	The check to build and optionally push the mentioned image to docker hub	✅ success
Docs check	Builds and tests the documentation	✅ success
Fast test	Normally this is the first check that is ran for a PR. It builds ClickHouse and runs most of stateless functional tests, omitting some. If it fails, further checks are not started until it is fixed. Look at the report to see which tests fail, then reproduce the failure locally as described here	✅ success
Flaky tests	Checks if new added or modified tests are flaky by running them repeatedly, in parallel, with more randomization. Functional tests are run 100 times with address sanitizer, and additional randomization of thread scheduling. Integration tests are run up to 10 times. If at least once a new test has failed, or was too long, this check will be red. We don't allow flaky tests, read the doc	✅ success
Install packages	Checks that the built packages are installable in a clear environment	✅ success
Integration tests	The integration tests report. In parenthesis the package type is given, and in square brackets are the optional part/total tests	✅ success
Stateful tests	Runs stateful functional tests for ClickHouse binaries built in various configurations -- release, debug, with sanitizers, etc	✅ success
Stateless tests	Runs stateless functional tests for ClickHouse binaries built in various configurations -- release, debug, with sanitizers, etc	✅ success
Stress test	Runs stateless functional tests concurrently from several clients to detect concurrency-related errors	✅ success
Style check	Runs a set of checks to keep the code style clean. If some of tests failed, see the related log from the report	✅ success
Unit tests	Runs the unit tests for different release types	✅ success
Upgrade check	Runs stress tests on server version from last release and then tries to upgrade it to the version from the PR. It checks if the new server can successfully startup without any errors, crashes or sanitizer asserts	✅ success

[vdimir]

Performance Comparison (release) [1/4] — 2 errors Details

Query just stuck for 15 seconds

Details

left-server-log.log
879168:2024.08.27 00:35:05.191062 [ 1059 ] {lower_upper_utf8.query1.run0} <Debug> executeQuery: (from [::1]:54134) SELECT upperUTF8(SearchPhrase) FROM hits_100m_single FORMAT Null (stage: Complete)
879169:2024.08.27 00:35:05.191454 [ 1059 ] {lower_upper_utf8.query1.run0} <Trace> Planner: Query to stage Complete
879170:2024.08.27 00:35:05.191518 [ 1059 ] {lower_upper_utf8.query1.run0} <Trace> Planner: Query from stage FetchColumns to stage Complete
879171:2024.08.27 00:35:05.191631 [ 1059 ] {lower_upper_utf8.query1.run0} <Debug> default.hits_100m_single (SelectExecutor): Key condition: unknown
879172:2024.08.27 00:35:05.191648 [ 1059 ] {lower_upper_utf8.query1.run0} <Debug> default.hits_100m_single (SelectExecutor): MinMax index condition: unknown
879173:2024.08.27 00:35:05.191666 [ 1059 ] {lower_upper_utf8.query1.run0} <Trace> default.hits_100m_single (SelectExecutor): Filtering marks by primary and secondary keys
879174:2024.08.27 00:35:05.191682 [ 1059 ] {lower_upper_utf8.query1.run0} <Debug> default.hits_100m_single (SelectExecutor): Selected 1/1 parts by partition key, 1 parts by primary key, 12208/12208 marks by primary key, 12208 marks to read from 1 ranges
879175:2024.08.27 00:35:05.191692 [ 1059 ] {lower_upper_utf8.query1.run0} <Trace> default.hits_100m_single (SelectExecutor): Spreading mark ranges among streams (default reading)
879176:2024.08.27 00:35:05.191790 [ 1059 ] {lower_upper_utf8.query1.run0} <Debug> default.hits_100m_single (SelectExecutor): Reading approx. 100007936 rows with 12 streams
879259:2024.08.27 00:35:20.280962 [ 1059 ] {lower_upper_utf8.query1.run0} <Error> executeQuery: Code: 159. DB::Exception: Timeout exceeded: elapsed 15.086713714 seconds, maximum: 15. (TIMEOUT_EXCEEDED) (version 24.9.1.1324 (official build)) (from [::1]:54134) (in query: SELECT upperUTF8(SearchPhrase) FROM hits_100m_single FORMAT Null), Stack trace (when copying this message, always include the lines below):
879272:2024.08.27 00:35:20.281236 [ 1059 ] {lower_upper_utf8.query1.run0} <Error> TCPHandler: Code: 159. DB::Exception: Timeout exceeded: elapsed 15.086713714 seconds, maximum: 15. (TIMEOUT_EXCEEDED), Stack trace (when copying this message, always include the lines below):
879285:2024.08.27 00:35:20.281282 [ 1059 ] {lower_upper_utf8.query1.run0} <Debug> TCPHandler: Processed in 15.090434938 sec.
879286:2024.08.27 00:35:20.281314 [ 1059 ] {lower_upper_utf8.query1.run0} <Debug> MemoryTracker: Peak memory usage (for query): 40.11 MiB.

I have a suspicion that cgroups memory observer doesn't work properly in perf tests (due to running two servers), let's try to disable it #68957