enh(last): enable using cache when select last and composite key

[Tony2h]

Description

Please briefly describe the code changes in this pull request.

Checklist

Please check the items in the checklist if applicable.

• Is the user manual updated?
• Are the test cases passed and automated?
• Is there no significant decrease in test coverage?

[gemini-code-assist]

Summary of Changes

Hello @Tony2h, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the database query optimizer's logic for aggregate functions, specifically addressing how the LAST function interacts with non-primary key columns, particularly in the context of composite keys. The changes ensure that the optimizer correctly identifies and processes these columns, and new comprehensive test cases have been added to validate this improved behavior.

Highlights

• Query Optimizer Logic Update: Modified the lastRowScanOptCheckFuncList in planOptimizer.c to include a check for non-primary key columns (!pCol->isPk) when processing SELECT_VALUE functions, ensuring correct handling of aggregate functions.
• New Test Cases for LAST function: Added a new test method test_last_pk in test_agg_last.py to specifically validate the behavior of the LAST aggregate function when used with composite keys.
• Test Resources Added: Included new resource files, last_pk.in and last_pk.csv, which define the input SQL queries and their expected outputs for the test_last_pk test case.

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[gemini-code-assist]

Code Review

This pull request enhances the query optimizer to correctly apply the Last Row Scan optimization for queries that use the last() function on a timestamp column while also selecting a composite primary key column. The fix in planOptimizer.c ensures that composite key columns are not incorrectly identified as non-primary key columns, which previously blocked this optimization. A new Python test case, test_last_pk, has been added to validate this change, including EXPLAIN queries to confirm that the Last Row Scan is utilized as expected. The changes are logical and the accompanying test is thorough and relevant.

[CLAassistant]

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