⚡ Optimize incremental indexing array lookup to Map

[mbayue]

💡 What:
Optimized the incremental indexing array lookup in server/search/indexing-pipeline.ts by converting the inner O(M) Array.prototype.find() search inside Array.prototype.filter() into an O(1) Map.prototype.get() lookup.

🎯 Why:
The previous implementation filtered sourceFiles and inside the filter callback, it searched through prevItems using .find(). This resulted in O(N*M) time complexity, which scales poorly when processing a large number of files.

📊 Measured Improvement:
We ran a micro-benchmark using 20,000 source files and 20,000 previous items.

• Original Implementation: ~2,205 ms
• Optimized Implementation: ~14.18 ms
• Speedup: ~155x improvement over the baseline.

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PR created automatically by Jules for task 3760722590300373566 started by @mbayue

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Summary by cubic

Switched incremental indexing from an O(N*M) Array.prototype.find() inside Array.prototype.filter() to an O(1) lookup using a precomputed Map keyed by file path in server/search/indexing-pipeline.ts. This makes change detection ~155x faster in a 20k-file benchmark.

^{Written for commit b059f87. Summary will update on new commits.}

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[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

Scanned Files

None

[cubic-dev-ai]

No issues found across 2 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

Architecture diagram

sequenceDiagram
    participant Pipeline as Incremental Indexing Pipeline
    participant SourceFiles as sourceFiles[]
    participant PrevItems as prevItems[]
    participant PrevItemsMap as NEW: prevItemsMap (Map)
    participant ModifiedOrAdded as modifiedOrAdded[]

    Note over Pipeline,ModifiedOrAdded: Optimized Change Detection Flow

    Pipeline->>PrevItems: Process previous index items
    PrevItems->>PrevItemsMap: Build Map keyed by path
    Note over PrevItemsMap: O(N) one-time build

    Pipeline->>SourceFiles: Iterate through current source files
    loop For each source file
        SourceFiles->>PrevItemsMap: Get by path
        alt Item exists in Map
            PrevItemsMap-->>Pipeline: prevItem (or undefined)
            Pipeline->>Pipeline: Compare SHA values
            alt SHA changed
                Pipeline->>ModifiedOrAdded: Add to result
            else SHA unchanged
                Pipeline->>Pipeline: Skip (no change)
            end
        else Item not in Map (new file)
            PrevItemsMap-->>Pipeline: undefined
            Pipeline->>ModifiedOrAdded: Add to result
        end
    end
    Pipeline-->>SourceFiles: Return modifiedOrAdded[]

    Note over Pipeline,ModifiedOrAdded: O(1) lookup per file (was O(M))

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