# M3.8.5 — Compression Benchmarks & Search Quality Validation

| Field | Value |
|---|---|
| Phase | M3.8 — Context optimization |
| Size | M — 1–2 days |
| Status | ⬜ Not started |
| Depends | M3.8.1, M3.8.2, M3.8.3 |
| Blocks | M3.8.6 |

## Goal

Validate that M3.8 optimization improves search quality (pgvector + OpenSearch)
without sacrificing performance.

## Deliverables

### 1. Compression Ratio Benchmarks

Test file: `crates/mem-ingest/tests/it_optimizer_benchmarks.rs` (200 LOC)

Benchmark each content type on real ingest sources:

```rust
#[tokio::test]
async fn benchmark_pi_session_compression() {
    // Load real Pi session transcript
    let source = PiSessionSource::new("fixtures/transcripts/pi-session-sample.json")?;
    
    let optimizer = ContextOptimizer::new()?;
    let metrics = Arc::new(Mutex::new(OptimizationMetrics::default()));
    
    let mut stream = source.records();
    while let Some(record) = stream.next().await {
        let _ = optimize_record_with_metrics(record?, &optimizer, &metrics)?;
    }
    
    let m = metrics.lock().unwrap();
    
    // Verify targets
    assert!(m.compression_ratio() >= 85.0, "log compression >= 85%");
    assert!(m.compression_ratio() <= 95.0, "log compression <= 95%");
    
    tracing::info!(
        ratio = m.compression_ratio(),
        "pi_session compression ratio"
    );
}
```

Tests (5):
- `benchmark_pi_session_compression` (log: 85-95%)
- `benchmark_claude_transcript_compression` (mixed: 60-80%)
- `benchmark_doc_corpus_compression` (text: 30-50%)
- `benchmark_aggregate_compression_all_sources`
- `benchmark_compression_ratio_per_compressor`

### 2. Search Quality Metrics

Test file: `tests/it_m3_8_search_quality.rs` (300 LOC)

Measure pgvector + OpenSearch impact of optimization:

```rust
#[tokio::test]
async fn test_pgvector_embedding_quality() {
    // Before optimization: noisy content
    let noisy = "ERROR: failed\nINFO: debug\nTRACE: verbose\nERROR: connection";
    let noisy_embedding = embed(noisy).await?;
    
    // After optimization: clean content
    let clean = "ERROR: failed\nERROR: connection";
    let clean_embedding = embed(clean).await?;
    
    // Measure similarity
    let similarity = cosine_similarity(&noisy_embedding, &clean_embedding);
    
    // Optimized version should be nearly identical
    // (stop words/debug lines don't carry semantic info)
    assert!(similarity > 0.95, "embeddings should be similar");
}
```

Tests (8):
- `test_pgvector_embedding_quality` (cosine similarity)
- `test_pgvector_vector_magnitude_preserved` (length variance)
- `test_opensearch_bm25_score_improvement` (ranking boost)
- `test_opensearch_noise_reduction` (fewer false matches)
- `test_hybrid_fusion_score_stability` (60% sem + 40% lex)
- `test_search_latency_with_optimization` (<10ms end-to-end)
- `test_compression_does_not_break_semantic_meaning`
- `test_multi_chunk_search_consistency`

### 3. Performance Baseline

Measure optimization overhead:

```rust
#[tokio::test]
async fn test_optimization_latency_p99() {
    let optimizer = ContextOptimizer::new()?;
    let mut latencies = Vec::new();
    
    for i in 0..1000 {
        let record = make_large_record();  // 10KB+ content
        
        let start = std::time::Instant::now();
        let _optimized = optimizer.optimize(&record.text)?;
        latencies.push(start.elapsed());
    }
    
    latencies.sort();
    let p99 = latencies[990];  // 99th percentile
    
    assert!(p99 < Duration::from_millis(3), "p99 latency < 3ms");
    
    tracing::info!(
        p50_ms = latencies[500].as_secs_f64() * 1000.0,
        p99_ms = p99.as_secs_f64() * 1000.0,
        "optimization latency"
    );
}
```

Tests (3):
- `test_optimization_latency_p99` (<3ms)
- `test_throughput_sustained` (1000+ records/sec)
- `test_memory_usage_bounded` (<100MB cache)

### 4. Test Fixtures

Create test data in `fixtures/benchmarks/`:

- `pi-session-sample.json` — Real Pi transcript (varies: 80-95% compression)
- `claude-transcript.json` — Claude chat (varies: 60-85% compression)
- `markdown-docs.txt` — Markdown content (varies: 40-60% compression)
- `json-output.json` — Structured data (varies: 70-90% compression)
- `mixed-logs.txt` — Mixed log output (varies: 85-95% compression)

### 5. Summary Report

After benchmarks run, generate `docs/M3.8.5-BENCHMARKS.md`:

```markdown
# M3.8 Compression Benchmarks

## Compression Ratios

| Content Type | Target | Measured | Status |
|---|---|---|---|
| Logs | 85-95% | 89.2% | ✅ |
| JSON | 70-90% | 78.5% | ✅ |
| Text | 30-50% | 42.1% | ✅ |
| Diffs | 60-80% | 71.3% | ✅ |
| Mixed | 60-75% | 68.9% | ✅ |

## Search Quality Impact

- pgvector embedding similarity: 0.96 (before vs after)
- OpenSearch BM25 ranking: +18% MRR
- Hybrid search fusion: stable

## Performance

- Latency p99: 1.8ms
- Throughput: 1200 records/sec
- Cache memory: 32MB typical
```

## Acceptance Criteria

✅ All compression targets met (measured >= target)
✅ 16 new tests (5 compression + 8 search + 3 perf)
✅ No performance regressions (<3ms per record)
✅ Search quality improves (pgvector + OpenSearch)
✅ Benchmark report generated
✅ Fixtures checked in (reusable for future A/B testing)

## Success Metrics

- Compression ratio: log 89.2%, json 78.5%, text 42.1%
- Embedding similarity: >0.95 (noisy vs clean)
- Search latency: <10ms end-to-end
- Optimization overhead: <2ms p99