Antalya 26.3 Backport of #101278, #102337 - Multiple Iceberg fixes

[mkmkme]

Note for reviewer

I wanted to apply only 102337 initially, but it caused conflicts due to missing changes from 101278. Therefore I decided to apply both of them at once.

Changelog category (leave one):

• Critical Bug Fix (crash, data loss, RBAC) or LOGICAL_ERROR

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

Fix Logical error: 'partitions_count > 0' exception when performing consecutive ALTER TABLE UPDATE on a partitioned Iceberg table (ClickHouse#101278 by @Desel72).
Fix crash in IcebergLocal ALTER TABLE ... UPDATE when using Avro format, caused by LowCardinality/Nullable wrapper types not being unwrapped before serialization (ClickHouse#102337 by @Desel72).

Documentation entry for user-facing changes

...

CI/CD Options

Exclude tests:

• Fast test
• Integration Tests
• Stateless tests
• Stateful tests
• Performance tests
• All with ASAN
• All with TSAN
• All with MSAN
• All with UBSAN
• All with Coverage
• All with Aarch64
• All Regression
• Disable CI Cache

Regression jobs to run:

• Fast suites (mostly <1h)
• Aggregate Functions (2h)
• Alter (1.5h)
• Benchmark (30m)
• ClickHouse Keeper (1h)
• Iceberg (2h)
• LDAP (1h)
• Parquet (1.5h)
• RBAC (1.5h)
• SSL Server (1h)
• S3 (2h)
• S3 Export (2h)
• Swarms (30m)
• Tiered Storage (2h)

[github-actions]

Workflow [PR], commit [241666c]

[alsugiliazova]

Verification: PR #1773

PR-added tests — all GREEN

2 tests × 6 stateless jobs each = 12 OK runs, 0 failures. (1 SKIPPED per test in Fast test, as expected.)

Test	Stateless runs	Status
04061_iceberg_update_partition_key_empty_block	6	all OK
04092_iceberg_update_low_cardinality	6	all OK

Jobs covered: amd_asan distributed-plan parallel, amd_debug distributed-plan s3 storage parallel, amd_debug parallel, arm_asan azure parallel, arm_asan targeted, arm_binary parallel.

Both new Iceberg-mutation code paths have clean positive coverage.

CI overview (head commit)

• PR test workflow: 42 success / 51 skipped / 3 failure
• Regression workflow: 30 success / 66 skipped / 4 failure (chronic baseline)
• One pending action_required job (queue/auth)

PR test-workflow failures

Check	Verdict
Integration tests (amd_asan, db disk, old analyzer, 3/6) — 24 × test_s3_cluster/test.py::*	Cascade failure (same shard, same timestamp). Recurring antalya-26.3 pattern on PRs 1772/1767/1757/1741/1731/1692. Not PR-caused (PR diff is in Iceberg/Mutations.cpp, not s3Cluster).
Integration tests (amd_asan, db disk, old analyzer, 4/6) — test_replicated_database/test.py::test_sync_replica	Pre-existing flake (56 fails / 29 PRs in 30d). Unrelated.
Stateless tests (arm_asan, azure, sequential, 2/2) — 03443_shared_storage_snapshots	Pre-existing flake (29 fails / 17 PRs in 30d). Unrelated.

Regression-workflow failures (chronic baseline on antalya-26.3)

Suite	Fails
Swarms (Aarch64 + Release)	227
Parquet (Aarch64 + Release)	34
S3Export partition (Aarch64 + Release)	20
S3Export part (Aarch64 + Release)	14

Same fingerprint as sibling antalya-26.3 PRs (1772, 1771, 1770, 1769, 1767, …). No new failure modes.

Caveat — partial frontport

This PR lands on antalya-26.3 while companion features from antalya-26.1 are still being frontported in parallel. Final re-verify recommended once the rest of the bundle lands.

Verdict

Safe to merge.

• Both PR-added tests pass 100% (12/12 stateless runs) for empty-partition-block and LowCardinality UPDATE paths.
• All test-level failures are well-known pre-existing flakes (test_sync_replica, 03443_shared_storage_snapshots) or the recurring test_s3_cluster shard-3/6 cascade.
• Regression failures match the chronic antalya-26.3 baseline.

[alsugiliazova]

Audit: PR #1773 — Antalya 26.3 Backport of #101278 + #102337 — Multiple Iceberg fixes

AI audit note: This review comment was generated by AI (Cursor agent, audit-review skill).

Confirmed defects

No confirmed defects in reviewed scope.