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Handle NULLs in ALTER MODIFY COLUMN#84770

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vdimir merged 2 commits intomasterfrom
vdimir/modify_column_null_to_default
Dec 15, 2025
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Handle NULLs in ALTER MODIFY COLUMN#84770
vdimir merged 2 commits intomasterfrom
vdimir/modify_column_null_to_default

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@vdimir vdimir commented Jul 31, 2025 •
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Changelog category (leave one):

  • Backward Incompatible Change

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

ALTER MODIFY COLUMN now requires explicit DEFAULT when converting nullable columns to non-nullable types. Previously such ALTERs could get stuck with cannot convert null to not null errors, now NULLs are replaced with column's default expression. Resolves #5985

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Close #5985

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clickhouse-gh bot commented Jul 31, 2025 •
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Workflow [PR], commit [cd53684]

Summary: ❌

job_name test_name status info comment
BuzzHouse (amd_msan) failure
Logical error: '(isConst() || isSparse() || isReplicated()) ? getDataType() == rhs.getDataType() : typeid(*this) == typeid(rhs)' FAIL cidb, issue
Integration tests (amd_asan, db disk, old analyzer, 3/6) error
OOM in dmesg FAIL cidb

@clickhouse-gh clickhouse-gh bot added the pr-backward-incompatible Pull request with backwards incompatible changes label Jul 31, 2025
@antaljanosbenjamin antaljanosbenjamin self-assigned this Jul 31, 2025
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antaljanosbenjamin approved these changes Jul 31, 2025
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LGTM.

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den-crane commented Jul 31, 2025

@vdimir vdimir force-pushed the vdimir/modify_column_null_to_default branch from 23a2bdd to ff270c5 Compare August 18, 2025 07:31
@vdimir vdimir force-pushed the vdimir/modify_column_null_to_default branch from f3140f1 to 238dcbb Compare September 3, 2025 13:10
@vdimir vdimir enabled auto-merge September 3, 2025 13:11
@vdimir vdimir force-pushed the vdimir/modify_column_null_to_default branch from 6b5c46e to 6ab2401 Compare December 11, 2025 14:07
@ClickHouse ClickHouse deleted a comment from clickhouse-gh bot Dec 11, 2025
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vdimir commented Dec 15, 2025

Integration tests (amd_asan, db disk, old analyzer, 3/6) error
OOM in dmesg FAIL cidb

Seems like #84881

@vdimir vdimir added this pull request to the merge queue Dec 15, 2025
Merged via the queue into master with commit 58d29ac Dec 15, 2025
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@vdimir vdimir deleted the vdimir/modify_column_null_to_default branch December 15, 2025 16:04
@robot-ch-test-poll robot-ch-test-poll added the pr-synced-to-cloud The PR is synced to the cloud repo label Dec 15, 2025
@bakwc bakwc mentioned this pull request Jan 3, 2026
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bakwc commented Jan 3, 2026

Hi team,
just a heads-up that the recent changes appear to have broken backward compatibility.
We spent quite a bit of time investigating an issue on our side before realizing it was related to changes in ClickHouse.
It would be greatly appreciated if the impact on existing integrations and dependent projects could be considered in future updates. Thank you!

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antaljanosbenjamin commented Jan 5, 2026

just a heads-up that the recent changes appear to have broken backward compatibility.

Hey! Did it broke in a way that is not mentioned in the changelog item? If yes, we have a problem. If not, then it is kind of expected.

Unfortunately from time to time we have to bite the bullet to introduce backward incompatible changes in order to fix big issues, in this case stuck mutations. We try to keep backward incompatible changes minimal and try to always add a proper changelog item, however we might mistakes (not noticing backward incompatibility or missing parts of the scope).

zvonand pushed a commit to Altinity/ClickHouse that referenced this pull request Jan 15, 2026
@vdimir @zvonand
Merge pull request ClickHouse#84770 from ClickHouse/vdimir/modify_col…
c02739b 
…umn_null_to_default

Handle NULLs in ALTER MODIFY COLUMN
@zvonand zvonand mentioned this pull request Jan 15, 2026
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25 tasks
zvonand pushed a commit to Altinity/ClickHouse that referenced this pull request Jan 27, 2026
@vdimir @zvonand
Merge pull request ClickHouse#84770 from ClickHouse/vdimir/modify_col…
08f97b7 
…umn_null_to_default

Handle NULLs in ALTER MODIFY COLUMN
@zvonand zvonand mentioned this pull request Jan 27, 2026
Merged
25 tasks
zvonand added a commit to Altinity/ClickHouse that referenced this pull request Jan 30, 2026
@zvonand
Merge pull request #1344 from Altinity/backports/25.8.15/84770
89bfe4f 
25.8.15 Stable backport of ClickHouse#84770: Handle NULLs in ALTER MODIFY COLUMN
zvonand pushed a commit to Altinity/ClickHouse that referenced this pull request Feb 5, 2026
@vdimir @zvonand
Merge pull request ClickHouse#84770 from ClickHouse/vdimir/modify_col…
2165a97 
…umn_null_to_default

Handle NULLs in ALTER MODIFY COLUMN
@zvonand zvonand mentioned this pull request Feb 5, 2026
Merged
25 tasks
zvonand added a commit to Altinity/ClickHouse that referenced this pull request Feb 7, 2026
@zvonand
Merge pull request #1370 from Altinity/backports/24.8.14/84770
b63d329 
24.8.14 Backport of ClickHouse#84770: Handle NULLs in ALTER MODIFY COLUMN
zvonand pushed a commit to Altinity/ClickHouse that referenced this pull request Mar 17, 2026
@vdimir @zvonand
Merge pull request ClickHouse#84770 from ClickHouse/vdimir/modify_col…
81628aa 
…umn_null_to_default

Handle NULLs in ALTER MODIFY COLUMN
@zvonand zvonand mentioned this pull request Mar 17, 2026
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Alter of nullable columns to not nullable is not supported

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