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Fix missing stream exception for nested JSON in wide parts#100475

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Avogar merged 1 commit intoClickHouse:masterfrom
Avogar:fix-nested-json-shared-data-missing-stream
Mar 24, 2026
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Fix missing stream exception for nested JSON in wide parts#100475
Avogar merged 1 commit intoClickHouse:masterfrom
Avogar:fix-nested-json-shared-data-missing-stream

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@Avogar Avogar commented Mar 23, 2026

PR #97523 fixed ColumnObject::permute and ColumnDynamic::permute to propagate statistics, but left the same bug in filter, index, replicate, and scatter for both ColumnObject and ColumnDynamic.

When a top-level JSON column containing Array(JSON) is permuted during INSERT (e.g. MergeTree sorting with optimize_on_insert=0), the chain ColumnObject::permute → ColumnArray::permute → indexImpl → ColumnObject::index drops statistics on the inner JSON column. This causes a mismatch: enumerateStreams (stream creation) uses the block_sample column which retains statistics via cloneEmpty and chooses 1 bucket (empty shared data optimization), while serializeBinaryBulkStatePrefix (serialization) uses the permuted column without statistics and chooses N buckets. The subsequent write to bucket 1 fails with "Stream ... not found" (LOGICAL_ERROR).

Reported by customer on version 25.12.1.1459:

Code: 49. DB::Exception: Stream light_images.images.Array(JSON(max_dynamic_types=16, max_dynamic_paths=256)).object_shared_data.1.size1 not found. (LOGICAL_ERROR)

Changelog category (leave one):

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

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

Fix LOGICAL_ERROR exception "Stream ... not found" when inserting into a table with nested Array(JSON) columns in wide parts with optimize_on_insert=0.

Documentation entry for user-facing changes

  • Documentation is written (mandatory for new features)

@Avogar @claude
Fix missing stream exception for nested JSON in wide parts
0be0ba4 
PR ClickHouse#97523 fixed `ColumnObject::permute` and `ColumnDynamic::permute` to
propagate `statistics`, but left the same bug in `filter`, `index`,
`replicate`, and `scatter` for both `ColumnObject` and `ColumnDynamic`.

When a top-level JSON column containing `Array(JSON)` is permuted during
INSERT (e.g. MergeTree sorting with `optimize_on_insert=0`), the chain
`ColumnObject::permute` -> `ColumnArray::permute` -> `indexImpl` ->
`ColumnObject::index` drops statistics on the inner JSON column.

This causes a mismatch: `enumerateStreams` (stream creation) uses the
`block_sample` column which retains statistics via `cloneEmpty` and
chooses 1 bucket (empty shared data optimization), while
`serializeBinaryBulkStatePrefix` (serialization) uses the permuted
column without statistics and chooses N buckets. The subsequent write
to bucket 1 fails with "Stream ... not found" (LOGICAL_ERROR).

Co-Authored-By: Claude Opus 4.6 <[email protected]>
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clickhouse-gh bot commented Mar 23, 2026 •
edited by Avogar
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Workflow [PR], commit [0be0ba4]

Summary: ❌

job_name test_name status info comment
AST fuzzer (amd_debug, targeted) failure
Logical error: Filter column for arrayRemove was not evaluated as ColumnUInt8 but as A (STID: 3494-613d) FAIL cidb, issue ISSUE EXISTS
Stress test (amd_tsan) failure
Logical error: 'ReadBuffer is canceled. Can't read from it.' (STID: 2508-2913) FAIL cidb, issue ISSUE CREATED
AST fuzzer (amd_debug) failure
Logical error: Bad cast from type A to B (STID: 4185-5b0d) FAIL cidb, issue ISSUE EXISTS

AI Review

Summary

This PR fixes a real correctness bug by preserving JSON path statistics through filter, index, replicate, and scatter for ColumnObject and ColumnDynamic, preventing Stream ... not found LOGICAL_ERROR during inserts with nested Array(JSON) into wide parts. The code changes themselves look consistent and low-risk, but test coverage is incomplete for all changed transform paths.

Findings

  • ⚠️ Majors
    • [tests/queries/0_stateless/04054_json_nested_shared_data_buckets_missing_stream_bug.sql:5] The new regression test validates the permute -> index failure path, but this PR also changes filter, replicate, and scatter in both ColumnObject and ColumnDynamic. Without dedicated assertions for these paths, regressions in the additional touched methods can slip through.
    • Suggested fix: extend this test (or add sibling tests) to trigger and validate statistics propagation through filter, replicate, and scatter code paths as well.

Tests

  • ⚠️ Add targeted regression coverage for filter, replicate, and scatter transformations on nested Array(JSON) data, because these methods were changed in this PR and currently are not directly exercised.

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 ✅

Final Verdict

  • Status: ⚠️ Request changes
  • Minimum required actions:
    • Add regression coverage for the additional changed paths (filter, replicate, scatter) so all touched statistics-propagation paths are protected by tests.

@clickhouse-gh clickhouse-gh bot added pr-critical-bugfix pr-must-backport Pull request should be backported intentionally. Use this label with great care! labels Mar 23, 2026
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clickhouse-gh bot reviewed Mar 23, 2026
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Comment thread tests/queries/0_stateless/04054_json_nested_shared_data_buckets_missing_stream_bug.sql

SET allow_experimental_json_type = 1;

-- Regression test for a bug where ColumnObject::index (and filter/replicate/scatter)
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The regression test reproduces the permute -> index path, but this PR also changes filter, replicate, and scatter in both ColumnObject and ColumnDynamic. Please add focused coverage for those transformed-column paths as well, otherwise future regressions in those methods will not be caught.

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clickhouse-gh bot commented Mar 23, 2026

LLVM Coverage Report

Metric Baseline Current Δ
Lines 83.90% 83.90% +0.00%
Functions 24.50% 24.60% +0.10%
Branches 76.50% 76.50% +0.00%

PR changed lines: PR changed-lines coverage: 100.00% (33/33, 0 noise lines excluded)
Diff coverage report
Uncovered code

@scanhex12 scanhex12 self-assigned this Mar 23, 2026
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scanhex12 approved these changes Mar 23, 2026
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Comment thread tests/queries/0_stateless/04054_json_nested_shared_data_buckets_missing_stream_bug.sql
@@ -0,0 +1,42 @@
-- Tags: long

SET allow_experimental_json_type = 1;
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Redundant?

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@Avogar Avogar Mar 24, 2026

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Yes. But let's keep it, I need this PR to be backported for a customer in cloud, so don't want to wait for CI rerun

@Avogar Avogar added this pull request to the merge queue Mar 24, 2026
Merged via the queue into ClickHouse:master with commit f94a13b Mar 24, 2026
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@Avogar Avogar deleted the fix-nested-json-shared-data-missing-stream branch March 24, 2026 13:19
@robot-ch-test-poll2 robot-ch-test-poll2 added the pr-must-backport-synced The `*-must-backport` labels are synced into the cloud Sync PR label Mar 24, 2026
@robot-ch-test-poll1 robot-ch-test-poll1 added the pr-synced-to-cloud The PR is synced to the cloud repo label Mar 24, 2026
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Backport #100475 to 25.3: Fix missing stream exception for nested JSO…
d8593fa 
…N in wide parts
This was referenced Mar 24, 2026
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Backport #100475 to 25.8: Fix missing stream exception for nested JSO…
687e609 
…N in wide parts
This was referenced Mar 24, 2026
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@robot-clickhouse
Backport #100475 to 25.12: Fix missing stream exception for nested JS…
7937af9 
…ON in wide parts
This was referenced Mar 24, 2026
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@robot-clickhouse
Backport #100475 to 26.1: Fix missing stream exception for nested JSO…
aaa9d55 
…N in wide parts
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Backport #100475 to 26.2: Fix missing stream exception for nested JSO…
8446289 
…N in wide parts
This was referenced Mar 24, 2026
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@robot-clickhouse
Backport #100475 to 26.3: Fix missing stream exception for nested JSO…
e6508af 
…N in wide parts
@robot-clickhouse robot-clickhouse mentioned this pull request Mar 24, 2026
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@robot-ch-test-poll robot-ch-test-poll added the pr-backports-created Backport PRs are successfully created, it won't be processed by CI script anymore label Mar 24, 2026
clickhouse-gh bot added a commit that referenced this pull request Mar 24, 2026
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Merge pull request #100594 from ClickHouse/backport/26.1/100475
92bead1 
Backport #100475 to 26.1: Fix missing stream exception for nested JSON in wide parts
clickhouse-gh bot added a commit that referenced this pull request Mar 24, 2026
@clickhouse-gh
Merge pull request #100592 from ClickHouse/backport/25.12/100475
c75398f 
Backport #100475 to 25.12: Fix missing stream exception for nested JSON in wide parts
clickhouse-gh bot added a commit that referenced this pull request Mar 24, 2026
@clickhouse-gh
Merge pull request #100596 from ClickHouse/backport/26.2/100475
37b7b00 
Backport #100475 to 26.2: Fix missing stream exception for nested JSON in wide parts
Avogar added a commit that referenced this pull request Mar 24, 2026
@Avogar
Merge pull request #100598 from ClickHouse/backport/26.3/100475
1a95836 
Backport #100475 to 26.3: Fix missing stream exception for nested JSON in wide parts
Avogar added a commit that referenced this pull request Mar 24, 2026
@Avogar
Merge pull request #100590 from ClickHouse/backport/25.8/100475
80e3af2 
Backport #100475 to 25.8: Fix missing stream exception for nested JSON in wide parts
Avogar added a commit that referenced this pull request Mar 24, 2026
@Avogar
Merge pull request #100588 from ClickHouse/backport/25.3/100475
1334132 
Backport #100475 to 25.3: Fix missing stream exception for nested JSON in wide parts
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