fix: pivot extra columns on projection

[KKould]

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Summary

pivot would cause additional columns to be selected within the pivot's internal select when selecting individual columns, resulting in more columns than expected.

example:

CREATE OR REPLACE TABLE test_string_pivot (
    id INT,
    region VARCHAR(10),
    month VARCHAR(10),
    sales INT
);

INSERT INTO test_string_pivot VALUES
    (1, 'North', 'Jan', 100),
    (1, 'North', 'Mar', 300),
    (1, 'North', 'Feb', 200),
    (2, 'South', 'Jan', 150),
    (2, 'South', 'Mar', 350),
    (2, 'South', 'Feb', 250);

# It only needs 2 columns but returned 7 columns.
query ITIII
SELECT id, region FROM test_string_pivot PIVOT (
    SUM(sales) FOR month IN (ANY ORDER BY month)
)
ORDER BY id, region;
----
1 North 1 North 200 100 300
2 South 2 South 250 150 350

Tests

• Unit Test
• Logic Test
• Benchmark Test
• No Test - Explain why

Type of change

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Breaking Change (fix or feature that could cause existing functionality not to work as expected)
• Documentation Update
• Refactoring
• Performance Improvement
• Other (please describe):

---

This change is 

[chatgpt-codex-connector]

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