Select Distinct support in JSON query

[robinskil]

This pull request updates the handling of the distinct field in query requests, enabling support for more advanced distinct queries by introducing a new Distinct struct. The changes also update the query planning logic to use this new structure, allowing for distinct operations on specific columns with custom select expressions.

Distinct query support:

• Changed the distinct field in QueryBody from an Option<Vec<String>> to an Option<Distinct>, and introduced a new Distinct struct with on and select fields to specify which columns to apply distinct on and which columns to select. (beacon-query/src/lib.rs)
• Updated the query planning logic to use the new Distinct struct: now, if a distinct clause is present, the planner builds expressions for both the on and select fields, and applies them using distinct_on. (beacon-query/src/parser.rs)

Code cleanup:

• Removed unused imports from beacon-query/src/parser.rs for clarity and maintainability.

Minor fix:

• Fixed the way the schema is passed to filter parsing functions for consistency. (beacon-query/src/parser.rs)

[Copilot]

Pull Request Overview

This pull request enhances the query system to support more advanced distinct operations by replacing the simple string-based distinct field with a structured approach. The changes enable specifying both the columns to apply distinct on and the columns to select, providing greater flexibility for distinct queries.

• Introduced a new Distinct struct with on and select fields to replace the simple Vec<String> distinct field
• Updated query planning logic to handle the new distinct structure using distinct_on operations
• Cleaned up unused imports and fixed schema parameter passing consistency

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
beacon-query/src/lib.rs	Introduces the new Distinct struct and updates QueryBody to use it instead of Vec<String>
beacon-query/src/parser.rs	Updates query planning logic to handle the new distinct structure, removes unused imports, and fixes schema parameter passing

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[Copilot]

[nitpick] The repeated pattern of mapping to_expr(&session.state()) and collecting results could be extracted into a helper function to reduce code duplication and improve maintainability.