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Greptile Overview

Greptile Summary

This PR fixes result caching for histogram queries by addressing several interconnected issues:

• Histogram interval handling in cache calculations: Added histogram_interval parameter to calculate_deltas to properly handle time boundaries for histogram buckets. When histogram interval is set, delta start time now uses result_meta.end_time directly instead of adding 1 microsecond, preventing overlap between cached and fetched data.

• Cache hit filtering fix: In get_cached_results, the hit filtering logic now accounts for histogram interval width (hit_ts + histogram_interval < hits_allowed_end_time) ensuring histogram buckets that span beyond the query end time are properly excluded.

• Cache time range adjustment for histograms: Added need_adjust_end_time flag in write_results to track when end time was aligned to histogram boundaries, then restore the full interval at cache write time to ensure complete buckets are stored.

• Partition generation threshold change: Relaxed the partition alignment condition from duration > self.min_step * 3 to duration > self.min_step, allowing alignment for smaller time ranges.

• Removed cache file deletion: Removed the mismatched-interval cache file deletion logic from do_partitioned_search. Per PR description, the new approach uses only aggregation cache files with intervals not greater than the search interval rather than deleting old files.

• Added PartialOrd to Interval enum: Enables interval comparison for the new cache selection strategy.

Confidence Score: 4/5

• This PR is safe to merge with thorough testing of histogram caching edge cases
• The changes are well-targeted fixes for histogram result caching issues. The logic changes are sound - accounting for histogram bucket widths in cache hit filtering and delta calculations. The removal of cache file deletion in favor of interval comparison is a cleaner approach. Minor concern around the relaxed partition alignment threshold which may need verification.
• Pay attention to src/service/search/cache/mod.rs and src/service/search/partition.rs - verify the time range adjustment and partition threshold changes work correctly for edge cases with small durations.

Important Files Changed

File Analysis

Sequence Diagram

sequenceDiagram
    participant Client
    participant SearchService
    participant CacheChecker as Cache Checker
    participant CacheWriter as Cache Writer
    participant PartitionGen as Partition Generator

    Client->>SearchService: Search Request (histogram)
    SearchService->>CacheChecker: check_cache(query, histogram_interval)
    CacheChecker->>CacheChecker: get_cached_results()
    
    alt Cache Hit
        CacheChecker->>CacheChecker: Filter hits by interval-adjusted boundaries
        CacheChecker->>CacheChecker: calculate_deltas(histogram_interval)
        CacheChecker-->>SearchService: CachedQueryResponse + deltas
    else Cache Miss
        CacheChecker-->>SearchService: Empty response
    end

    SearchService->>PartitionGen: generate_partitions_aligned_with_histogram_interval()
    PartitionGen->>PartitionGen: Align start/end to min_step boundaries
    PartitionGen-->>SearchService: Partitions

    SearchService->>SearchService: Execute search for delta partitions
    
    SearchService->>CacheWriter: write_results()
    CacheWriter->>CacheWriter: Align time range to histogram interval
    CacheWriter->>CacheWriter: Filter hits within accept range
    CacheWriter->>CacheWriter: Adjust end_time if need_adjust_end_time
    CacheWriter->>CacheWriter: Cache to disk with aligned timestamps

    SearchService-->>Client: Merged results (cached + fresh)

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