Add comprehensive benchmarking framework for DTail

- Create benchmark framework to measure performance of dcat, dgrep, and dmap
- Generate test files of 10MB, 100MB, and 1GB with configurable patterns
- Support benchmarking with gzip and zstd compressed files
- Implement tool-specific benchmarks:
  * DCat: Simple reading, multiple files, compressed files
  * DGrep: Pattern matching, regex complexity, context lines, inverted grep
  * DMap: Aggregations, group by operations, complex queries, time intervals
- Track performance metrics: throughput (MB/sec), lines/sec, memory usage
- Save results in multiple formats: JSON, CSV, and Markdown reports
- Add Makefile targets: benchmark, benchmark-quick, benchmark-full
- Support environment variables for configuration (sizes, timeouts, etc.)
- Automatically clean up temporary .tmp files after benchmarks

The framework provides consistent performance testing across the DTail toolset
and enables tracking performance regressions between commits.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

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+# DTail Benchmarks
+
+This directory contains comprehensive benchmarks for the DTail toolset (dcat, dgrep, dmap).
+
+## Overview
+
+The benchmarking framework tests performance across:
+- Different file sizes (10MB, 100MB, 1GB)
+- Various compression formats (none, gzip, zstd)
+- Different query patterns and complexities
+- Server mode vs serverless operation
+
+## Prerequisites
+
+Before running benchmarks, ensure all DTail binaries are built:
+
+```bash
+cd ..
+make build
+```
+
+## Running Benchmarks
+
+### Quick Benchmarks (Small Files Only)
+```bash
+go test -bench=BenchmarkQuick ./benchmarks
+```
+
+### All Benchmarks
+```bash
+go test -bench=. ./benchmarks
+```
+
+### Specific Tool Benchmarks
+```bash
+# DCat benchmarks only
+go test -bench=BenchmarkDCat ./benchmarks
+
+# DGrep benchmarks only
+go test -bench=BenchmarkDGrep ./benchmarks
+
+# DMap benchmarks only
+go test -bench=BenchmarkDMap ./benchmarks
+```
+
+### With Memory Profiling
+```bash
+go test -bench=. -benchmem ./benchmarks
+```
+
+### Custom Configuration
+```bash
+# Run with specific file sizes
+DTAIL_BENCH_SIZES=small,medium go test -bench=. ./benchmarks
+
+# Keep temporary files for inspection
+DTAIL_BENCH_KEEP_FILES=true go test -bench=. ./benchmarks
+
+# Set custom timeout
+DTAIL_BENCH_TIMEOUT=30m go test -bench=. ./benchmarks
+```
+
+## Benchmark Categories
+
+### DCat Benchmarks
+- **Simple**: Sequential file reading
+- **Multiple Files**: Reading 10-100 files concurrently
+- **Compressed**: Performance with gzip/zstd compression
+- **Server Mode**: Client-server performance comparison
+
+### DGrep Benchmarks
+- **Simple Pattern**: Basic string matching with varying hit rates
+- **Regex Pattern**: Complex regex performance
+- **Context Lines**: Impact of --before/--after flags
+- **Inverted**: Performance of --invert grep
+- **Compressed**: Grep on compressed files
+
+### DMap Benchmarks
+- **Simple Aggregation**: Basic count, sum, avg operations
+- **Group By Cardinality**: Performance with different group sizes
+- **Complex Queries**: WHERE clauses and multiple conditions
+- **Time Intervals**: Time-based grouping performance
+- **Custom Functions**: Performance of maskdigits, md5sum, etc.
+
+## Output
+
+Benchmark results are saved in multiple formats:
+- `benchmark_results/results_TIMESTAMP.json` - Machine-readable JSON
+- `benchmark_results/results_TIMESTAMP.csv` - Spreadsheet-compatible CSV
+- `benchmark_results/results_TIMESTAMP.md` - Human-readable Markdown report
+- `benchmark_results/latest.json` - Most recent results for easy access
+
+## Interpreting Results
+
+Key metrics:
+- **MB/sec**: Throughput in megabytes per second
+- **lines/sec**: Lines processed per second
+- **compression_ratio**: For compressed file benchmarks
+- **matched_lines**: For grep benchmarks
+- **approx_groups**: For MapReduce group by operations
+
+## Performance Tuning
+
+For accurate benchmarks:
+1. Run on isolated hardware
+2. Disable CPU frequency scaling
+3. Close unnecessary applications
+4. Run multiple times and average results
+
+## Continuous Integration
+
+The benchmarks can be integrated into CI/CD pipelines:
+
+```yaml
+# Example GitHub Actions workflow
+- name: Run Benchmarks
+  run: |
+    make build
+    go test -bench=BenchmarkQuick ./benchmarks
+```
+
+## Troubleshooting
+
+### "Command not found" errors
+Ensure DTail binaries are built: `make build`
+
+### Disk space issues
+Benchmarks create large temporary files. Ensure sufficient disk space (>2GB).
+
+### Timeout errors
+Increase timeout: `DTAIL_BENCH_TIMEOUT=60m go test -bench=. ./benchmarks`
+
+## Contributing
+
+When adding new benchmarks:
+1. Follow existing naming conventions
+2. Include warmup runs
+3. Report relevant metrics
+4. Clean up temporary files
+5. Document in this README
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