fix SQL parser for math expressions

[robfrank]

This pull request updates the SQL grammar to improve how expressions are parsed, particularly by refining the lookahead rules for certain grammar productions. The main focus is on enhancing the handling of mathematical expressions and parenthesized where clauses.

Grammar parsing improvements:

• Updated the Expression rule in SQLGrammar.jjt to use a more precise lookahead for parenthesized WhereClause expressions, replacing a generic three-token lookahead with a specific pattern.
• Added lookahead for MathExpression in both the Expression and ArrayConcatExpressionElement rules, allowing mathematical expressions to be parsed correctly in these contexts. [1] [2]

[gemini-code-assist]

Summary of Changes

Hello @robfrank, 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 refines the SQL grammar's parsing logic, primarily focusing on improving the recognition and handling of mathematical expressions and parenthesized WHERE clauses. By introducing more specific lookahead rules, the changes aim to enhance the robustness and accuracy of the parser for these common SQL constructs.

Highlights

• Refined WhereClause Parsing: The Expression rule's lookahead for parenthesized WhereClause expressions has been updated from a generic LOOKAHEAD(3) to a more precise LOOKAHEAD( <LPAREN> WhereClause() <RPAREN> ), improving parsing accuracy.
• Enhanced MathExpression Handling: Specific lookahead rules for MathExpression have been added to both the Expression and ArrayConcatExpressionElement grammar productions, ensuring correct parsing of mathematical expressions in these contexts.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description
Code Review	/gemini review	Performs a code review for the current pull request in its current state.
Pull Request Summary	/gemini summary	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in pull request comments and review comments.
Help	/gemini help	Displays a list of available commands.

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for Github and other Google products, sign up here.

You can also get AI-powered code generation, chat, as well as code reviews directly in the IDE at no cost with the Gemini Code Assist IDE Extension.

Footnotes

1. Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution. ↩

[mergify]

🧪 CI Insights

Here's what we observed from your CI run for ba209f8.

🟢 All jobs passed!

But CI Insights is watching 👀

[gemini-code-assist]

Code Review

This pull request improves the SQL grammar by refining lookahead rules, which enhances the parser's ability to correctly handle mathematical and parenthesized expressions. The change from a numeric lookahead (LOOKAHEAD(3)) to a semantic lookahead (LOOKAHEAD( <LPAREN> WhereClause() <RPAREN> )) for parenthesized WhereClause is a significant improvement in robustness. Additionally, adding LOOKAHEAD(MathExpression()) in the Expression and ArrayConcatExpressionElement rules correctly resolves ambiguities, making the grammar more precise. The changes are well-implemented and address the described problem effectively. I have reviewed the changes and found no issues.

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
Report missing for 8f9ac7f1	✅ 91.32%

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (8f9ac7f)	Report Missing	Report Missing	Report Missing
Head commit (ba209f8)	75810	48457	63.92%

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#2918)	1670	1525	91.32%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

See your quality gate settings    Change summary preferences

Footnotes

1. Codacy didn't receive coverage data for the commit, or there was an error processing the received data. Check your integration for errors and validate that your coverage setup is correct. ↩