Add count distinct aggregate function

[parmesant]

Fixes #XXXX.

Description

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This PR has:

• been tested to ensure log ingestion and log query works.
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added documentation for new or modified features or behaviors.

Summary by CodeRabbit

• New Features
  • Added support for the CountDistinct aggregate function in alert evaluations. This allows users to create alerts based on the count of distinct values in a dataset.

[coderabbitai]

Walkthrough

Support for the CountDistinct aggregate function was added to the alert evaluation logic. This includes introducing a new CountDistinct variant to the AggregateFunction enum, updating its Display trait implementation, and extending the aggregate operation matching logic to handle CountDistinct.

Changes

File(s)	Change Summary
src/alerts/mod.rs	Added CountDistinct variant to AggregateFunction enum and updated its Display implementation.
src/alerts/alerts_utils.rs	Imported count_distinct function and extended aggregate operation matching for CountDistinct.

Sequence Diagram(s)

sequenceDiagram
    participant User
    participant AlertSystem
    participant DataFusion

    User->>AlertSystem: Define alert with CountDistinct aggregate
    AlertSystem->>AlertSystem: Detect AggregateFunction::CountDistinct
    AlertSystem->>DataFusion: Call count_distinct on column
    DataFusion-->>AlertSystem: Return distinct count result
    AlertSystem-->>User: Provide alert evaluation outcome

Loading

Poem

In the land of code, a function new,
CountDistinct joins the alerting crew.
Counting uniques with a clever twist,
No duplicate values will be missed.
The enum grows, the logic flows,
As distinct counts now proudly show!
🐇✨

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📥 Commits

Reviewing files that changed from the base of the PR and between f240dde and 838f0ed.

📒 Files selected for processing (2)

• src/alerts/alerts_utils.rs (2 hunks)
• src/alerts/mod.rs (2 hunks)

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🔇 Additional comments (4)

src/alerts/alerts_utils.rs (2)

22-22: Good addition of the count_distinct import.

The import statement correctly adds the count_distinct function from the datafusion library, which is needed for the new aggregate function.

---

390-390: Correctly implemented the CountDistinct aggregate function.

The match arm for AggregateFunction::CountDistinct has been properly implemented, using the imported count_distinct function with the column name. This completes the full implementation of the new aggregate function and follows the same pattern as the other aggregate functions.

src/alerts/mod.rs (2)

293-293: Good addition of the CountDistinct enum variant.

The new CountDistinct variant has been added to the AggregateFunction enum, which is necessary for supporting the count distinct aggregation operation.

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304-304: Correctly implemented the Display trait for CountDistinct.

The Display trait implementation for AggregateFunction has been updated to handle the new CountDistinct variant, ensuring it's properly formatted in error messages and logs.

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