Fix Iceberg read optimization returning NULLs for stats-less manifests

[il9ue]

Re-opened from Altinity/ClickHouse (instead of my fork) so CI publishes direct .deb package URLs for clickhouse-regression. Same commit (8b597ed) as #1814. Fork PRs don't receive repo secrets, so the S3 upload step was skipped on #1814 and CI only emitted the DEB_ARM_RELEASE artifact zip.

Changelog category (leave one):

• Bug Fix

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

Fix Iceberg read optimization returning NULL for every column when reading from manifests written without per-file column statistics (typical of non-Spark writers like pyiceberg with default settings). Affects icebergLocal, icebergS3, icebergAzure, icebergHDFS, and all *Cluster variants. Antalya 26.3 fix for #1545.

Documentation entry for user-facing changes

• Documentation is written (mandatory for new features)

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Antalya-specific bug fix on antalya-26.3. No upstream cherry-pick — this bug exists only on Antalya, introduced by #1069 ("Read optimization using Iceberg metadata"). Mirror of the 25.8 fix in #1688.

Why this fires

When reading an Iceberg table written by a non-Spark writer that omits per-file column statistics from the manifest's Avro schema (pyiceberg with default settings, format v1 writers, and others), the allow_experimental_iceberg_read_optimization path produces silent data loss: correct row counts, every column value NULL. Confirmed on icebergLocal; the same code path fires for icebergS3, icebergAzure, icebergHDFS, and all *Cluster variants.

Root cause

IcebergIterator always populates file_meta_info before yielding objects, so the file_meta_data.has_value() check in the optimization passes. The problem is what's inside the populated DataFileMetaInfo: when the manifest's data_file.value_counts / column_sizes / null_value_counts Avro fields are all absent (all three are optional per the Iceberg spec), DataFileMetaInfo::columns_info stays empty.

The optimization's second loop in StorageObjectStorageSource::createReader then iterates every requested column, finds none in the empty columns_info map, and adds them all to constant_columns_with_values with Field() (NULL). requested_columns_copy is cleared, need_only_count = true, the Parquet reader returns row count only, and generate() injects every column as a constant-NULL column at the correct row count. The optimization conflates "no stats were written" with "all columns are absent" — but absent stats tell us nothing about which columns are physically present.

The fix

Add any_stats_field_present (bool) to DataFileMetaInfo, populated during manifest parsing in AvroForIcebergDeserializer.cpp — true if any of value_counts, column_sizes, or null_value_counts were emitted. Gate the optimization's absent-NULL loop on this flag: when no stats were emitted, skip the loop and fall through to the Parquet reader, which correctly handles both physically-present columns (read normally) and schema-evolved-absent columns (handled upstream by IcebergMetadata::getInitialSchemaByPath setting the file's own schema as initial_header).

A per-column presence set was considered but is unnecessary — schema evolution is already handled upstream of the optimization, so the boolean is sufficient. JSON serialization (cluster reads via toJson() / JSON-ptr constructor) round-trips the new field; missing-on-deserialization defaults to false, matching pre-fix behavior.

Files changed

• src/Storages/ObjectStorage/DataLakes/IDataLakeMetadata.h — added any_stats_field_present to DataFileMetaInfo; constructor signature updated.
• src/Storages/ObjectStorage/DataLakes/IDataLakeMetadata.cpp — JSON serde round-trips the new field; defaults to false on missing.
• src/Storages/ObjectStorage/DataLakes/Iceberg/ManifestFile.h — header updates for ParsedManifestFileEntry.
• src/Storages/ObjectStorage/DataLakes/Common/AvroForIcebergDeserializer.cpp — tracks whether any stats Avro field was present during manifest parsing on 26.3.
• src/Storages/ObjectStorage/DataLakes/Iceberg/IcebergIterator.cpp — forwards the new bool when constructing DataFileMetaInfo.
• src/Storages/ObjectStorage/StorageObjectStorageSource.cpp — the absent-NULL loop now skips when any_stats_field_present is false.

Note: 26.3 uses AvroForIcebergDeserializer.cpp for manifest parsing where 25.8 / 26.1 use ManifestFile.cpp (file was split upstream). Same logic, different file.

Tested

Integration test tests/integration/test_storage_iceberg_no_spark/test_iceberg_read_optimization_empty_stats.py, ported from the 25.8 PR. Four scenarios:

• test_iceberg_local_returns_actual_rows_with_stats_less_manifest — reproducer, fails without the fix.
• test_iceberg_local_returns_correct_rows_when_optimization_disabled — control.
• test_iceberg_local_partial_stats_manifest_reads_correctly — manifest with value_counts only.
• test_iceberg_local_full_stats_manifest_reads_correctly — full Spark-style stats regression guard.

Closes #1545
Mirror of #1688 (antalya-25.8 fix).

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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)
• Tiered Storage (2h)

[github-actions]

Workflow [PR], commit [5ec03a9]

[alsugiliazova]

Audit update for PR #1895

AI audit note: This review comment was generated by AI (claude-opus-4.7).

Mirror of: Altinity/ClickHouse#1688 (antalya-25.8 fix). Closes Altinity/ClickHouse#1545. Re-open of the closed fork-based PR Altinity/ClickHouse#1814 (same commit 8b597ed / 5ec03a9), re-filed from a repo branch so CI secrets are available and the .deb package URLs are published for clickhouse-regression.

Confirmed defects

No confirmed defects in reviewed scope.

[alsugiliazova]

PR #1895 CI Verification — Fix Iceberg read optimization returning NULLs for stats-less manifests

• Head branch: fix/iceberg-empty-stats-26.3
• Head SHA: 5ec03a9700f77ba6dd465e84b4775d4a7e4323e9
• Verification date: 2026-06-11

Verdict

No PR-caused regressions identified. All red checks are infrastructure timeouts, pre-existing flaky tests, or a pre-existing UBSan bug in unrelated code (ToStartOfInterval integer overflow). The PR's own 4 new integration tests pass on every job that ran them across 5 build variants.

Job status summary (current SHA)

Status	Count
SUCCESS	564
FAILURE	13 (jobs + rollup rows)
ERROR	3
SKIPPED	199 (build matrix exclusions)

Failing checks on current SHA 5ec03a97 (latest run 27143685017)

#	Check	Failure	Category
1	Stress test (arm_asan, s3)	Cannot start clickhouse-server	Pre-existing flaky
2	AST fuzzer (amd_ubsan)	UBSan integer overflow in ToStartOfInterval<Year>	Pre-existing upstream bug, unrelated
3	Integration tests (amd_msan, 4/6)	Job-level error, 0 test fails	Harness timeout
4	Integration tests (arm_binary, distributed plan, 2/4)	Job-level error, 0 test fails	Harness timeout
5	SQLLogic test	Job-level error, 0 test fails	Harness timeout (3h limit)
6	RegressionTestsRelease / S3Export (part) / s3_export_part	could not bring up docker-compose cluster	Infrastructure

1. Stress test (arm_asan, s3) — pre-existing flake

• Test name Cannot start clickhouse-server: 88 failures across 34 unrelated PRs in the last 60 days (since 2026-04-30). Recurring infrastructure / startup flake.

2. AST fuzzer (amd_ubsan) — pre-existing upstream UBSan bug

• Stack trace from stderr.log:

/ClickHouse/src/Functions/DateTimeTransforms.h:817:79: runtime error:
  signed integer overflow: 9223372036854775806 * 12 cannot be represented in type 'Int64'
  #0  DB::ToStartOfInterval<(IntervalKind::Kind)10>::execute(...)  Functions/DateTimeTransforms.h:817
  #1  DB::FunctionToStartOfInterval::execute<DataTypeDate32, ...>  Functions/toStartOfInterval.cpp:437
  ...
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior

• The bug is in Functions/DateTimeTransforms.h and Functions/toStartOfInterval.cpp — completely unrelated to Iceberg / object storage code touched by this PR.
• AST fuzzer (amd_ubsan) "Unknown error" hits in last 60 days: PR=0 (master) ×4, plus PRs 1645, 1568, 1803, 1895 — generic recurring fuzzer bucket.
• This is a fuzzer-discovered upstream UBSan issue, not a regression introduced by PR Fix Iceberg read optimization returning NULLs for stats-less manifests #1895.

3–5. Integration tests (amd_msan 4/6, arm_binary distributed plan 2/4) and SQLLogic test — harness timeouts

All three jobs are reported as error in the database with 0 test failures — meaning every test that completed passed; the job itself was killed by the harness timeout.

From Integration tests (amd_msan, 4/6) job log:

[2026-06-08 22:32:51] PASSED test_multiple_disks/test.py::test_concurrent_alter_modify[mt]
[2026-06-08 22:36:10] PASSED test_multiple_disks/test.py::test_concurrent_alter_modify[replicated]
[2026-06-08 22:37:34] WARNING: Timeout exceeded [11400], sending SIGTERM to process group
[2026-06-08 22:49:53] PASSED test_ttl_replicated/test.py::test_ttl_drop_parts_limit
[2026-06-08 22:49:53] === 3 passed in 1218.94s ===
[2026-06-08 22:49:54] Test execution was interrupted (exit status: 2)

From SQLLogic test job log:

[2026-06-08 22:51:52] WARNING: Timeout exceeded [10800] for [3952]
[2026-06-08 22:51:55] WARNING: Job timed out: [SQLLogic test], timeout [10800], exit code [137]

All three are runner-level timeouts (3h / 11400s limits), not regressions. None of these jobs touch the Iceberg/StorageObjectStorageSource code path.

6. S3Export (part) regression suite — infrastructure failure

From the report:

/s3 Fail 52s could not bring up docker-compose cluster
/s3/minio Fail 52s could not bring up docker-compose cluster

The test environment failed to start in 52 seconds (no test ever ran). Pure infrastructure issue — completely independent of the PR's source change to Iceberg read optimization.

PR's own new tests — all passing

tests/integration/test_storage_iceberg_no_spark/test_iceberg_read_optimization_empty_stats.py includes 4 test cases:

• test_iceberg_local_full_stats_manifest_reads_correctly
• test_iceberg_local_partial_stats_manifest_reads_correctly
• test_iceberg_local_returns_correct_rows_when_optimization_disabled
• test_iceberg_local_returns_actual_rows_with_stats_less_manifest

All 4 tests passed in all 5 integration jobs that scheduled them on this SHA:

Check	Status (4/4 cases)
Integration tests (amd_tsan, 5/6)	OK
Integration tests (amd_msan, 5/6)	OK
Integration tests (amd_binary, 5/5)	OK
Integration tests (amd_asan, db disk, old analyzer, 5/6)	OK
Integration tests (arm_binary, distributed plan, 4/4)	OK

That is 20 / 20 PASS for the PR's own coverage — the fix's behavior is consistently exercised across debug, release, sanitizer, alternative-analyzer, and ARM builds.

Recommendations

1. Rerun the failing jobs to clear the harness-timeout reds:
   • Integration tests (amd_msan, 4/6)
   • Integration tests (arm_binary, distributed plan, 2/4)
   • SQLLogic test
2. Rerun Stress test (arm_asan, s3) to clear the known startup flake.
3. Rerun RegressionTestsRelease / S3Export (part) (infra docker-compose failure).
4. The AST fuzzer (amd_ubsan) UBSan finding in ToStartOfInterval is an upstream bug worth tracking separately, but does not block this PR — the touched code is unrelated.
5. Merge once jobs are green; no PR-introduced regressions detected.