#17593 Add Extension Points For Pre and Post Collection of Scores in QueryPhase

[atris]

Resolves #17593

Problem

Plugins implementing hybrid queries and neural search currently rely on AggregationProcessor workarounds to inject custom CollectorManager implementations. This approach is fragile and breaks when the aggregation system changes.

Solution

Add extension points directly in QueryPhase around the actual score collection operation:

• QueryPhaseExtension interface with beforeScoreCollection() and afterScoreCollection() methods
• Extension registration via QueryPhaseSearcher.queryPhaseExtensions()
• Execution in DefaultQueryPhaseSearcher with proper error isolation

Implementation

New interface:

@PublicApi(since = "3.0.0")
public interface QueryPhaseExtension {
    void beforeScoreCollection(SearchContext searchContext);
    void afterScoreCollection(SearchContext searchContext);
}

Extension points placed around:
searcher.search(query, collector) // <- actual score collection

Features:
- Extensions execute before and after score collection in try/finally blocks
- Individual extension failures are logged but don't break search
- Default implementations return empty extension lists (backward compatible)
- Zero overhead when no extensions are registered

Usage

public class HybridQueryPhaseSearcher extends DefaultQueryPhaseSearcher {
    @Override
    public List<QueryPhaseExtension> queryPhaseExtensions() {
        return List.of(new HybridQueryExtension(), new NeuralSearchExtension());
    }
}

Testing

Unit tests verify:

• Interface functionality
• Extension registration
• Integration with search execution
• Error handling and isolation

No existing functionality affected.

[atris]

@getsaurabh02

[github-actions]

❌ Gradle check result for da66380: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[owaiskazi19]

@atris now that we have a way to inject QueryCollectorContext in core, would that solve your need? #18278

[github-actions]

❌ Gradle check result for 0a0f121: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions]

✅ Gradle check result for 76fd57b: SUCCESS

[owaiskazi19]

@bugmakerrrrrr can you take another look and we can get this in?

[atris]

@bugmakerrrrrr Updated, please see and let me know

[github-actions]

❌ Gradle check result for bfad37b: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[atris]

@bugmakerrrrrr Please review.

[bugmakerrrrrr]

LGTM. Thanks @atris

[github-actions]

✅ Gradle check result for d4a5007: SUCCESS