Add IN PARTITION clause support for ALTER TABLE UPDATE

[Copilot]

Implements the IN PARTITION clause for ALTER TABLE ... UPDATE statements per ClickHouse SQL reference.

Changes

Parser

• Modified parseUpdateAssignment() to use parseSubExpr(pos, precedenceIn) instead of parseExpr(pos), preventing the expression parser from consuming the IN keyword as part of a binary operation
• Extended parseAlterTableUpdate() to parse optional IN PARTITION clause before WHERE clause (not after)

AST

• Added InPartition *PartitionClause field to AlterTableUpdate struct
• Updated String() method to output IN PARTITION before WHERE clause
• Updated Accept() and Walk() methods to handle the new field

Tests

• Added test cases covering simple partitions, PARTITION ID syntax, and multiple column assignments

Syntax

ALTER TABLE test.users 
UPDATE status = 'active' 
IN PARTITION '2024-01'
WHERE id > 100;

Note: The IN PARTITION clause appears between assignments and WHERE, not after WHERE.

The implementation preserves backward compatibility—standard expressions in assignments and WHERE clauses continue to work correctly.

Known Limitation

The ID keyword in PARTITION ID syntax is not preserved in formatted output (e.g., IN PARTITION ID '202401' formats as IN PARTITION '202401'). This is consistent with existing behavior in other ALTER commands due to PartitionClause.String() implementation.

• Fixes Add support of IN PARTITION expression for ALTER TABLE ... UPDATE #204

Original prompt

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This section details on the original issue you should resolve

<issue_title>Add support of IN PARTITION expression for ALTER TABLE ... UPDATE</issue_title>
<issue_description>For the detailed syntax, please refer to: https://clickhouse.com/docs/sql-reference/statements/alter/update</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Add support of IN PARTITION expression for ALTER TABLE ... UPDATE #204

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[git-hulk]

@copilot The correct syntax is follwoing:

ALTER TABLE [db.]table [ON CLUSTER cluster] UPDATE column1 = expr1 [, ...] [IN PARTITION partition_id] WHERE filter_expr

IN PARTITION should be parsed before WHERE keyword. Also, you need to search the codebase to see if we have parsed IN PARTITION before. If yes, reuse the parse function if possible.

[coveralls]

Pull Request Test Coverage Report for Build 18828241324

Details

• 23 of 31 (74.19%) changed or added relevant lines in 4 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.05%) to 50.281%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
parser/parser_alter.go	12	14	85.71%
parser/walk.go	2	4	50.0%
parser/ast.go	4	8	50.0%

Files with Coverage Reduction	New Missed Lines	%
parser/ast.go	1	39.89%

Totals
Change from base Build 18827715548:	0.05%
Covered Lines:	7521
Relevant Lines:	14958

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💛 - Coveralls

[Copilot]

@copilot The correct syntax is follwoing:

...

Fixed in commit 3ce2d80. The IN PARTITION clause is now parsed before the WHERE keyword as specified in the ClickHouse documentation.

The implementation:

• Moved IN PARTITION parsing to occur after assignments but before WHERE
• Used parseSubExpr(pos, precedenceIn) in parseUpdateAssignment to prevent the expression parser from consuming the IN keyword
• Updated the String() method to output the correct syntax order
• Reused existing tryParsePartitionClause function as suggested

All tests are passing with the corrected syntax:

ALTER TABLE table UPDATE column = value [IN PARTITION partition_id] WHERE condition

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