bench_test.go

package sntable_test

import (
	"bytes"
	"testing"

	"github.com/bsm/sntable"
)

// Benchmark_miss is the important one: it shows the bloom filter turning an
// absent-key lookup from a full block read+decompress into an in-memory bit
// check. Benchmark_hit shows the filter adds ~nothing on the hit path.
func Benchmark_bloom(b *testing.B) {
	const n = 200_000

	build := func(o *sntable.WriterOptions) *sntable.Reader {
		var buf bytes.Buffer
		w := sntable.NewWriter(&buf, o)
		val := make([]byte, 16)
		for i := range n {
			if err := w.Append(uint64(i*2), val); err != nil {
				b.Fatal(err)
			}
		}
		if err := w.Close(); err != nil {
			b.Fatal(err)
		}
		r, err := sntable.NewReader(bytes.NewReader(buf.Bytes()), int64(buf.Len()))
		if err != nil {
			b.Fatal(err)
		}
		return r
	}

	variants := []struct {
		name string
		opts *sntable.WriterOptions
	}{
		{"nobloom-snappy", &sntable.WriterOptions{Compression: sntable.SnappyCompression}},
		{"nobloom-plain", &sntable.WriterOptions{Compression: sntable.NoCompression}},
		{"bloom-snappy", &sntable.WriterOptions{Compression: sntable.SnappyCompression, BloomBitsPerKey: 10, BloomExpectedKeys: n}},
		{"bloom-plain", &sntable.WriterOptions{Compression: sntable.NoCompression, BloomBitsPerKey: 10, BloomExpectedKeys: n}},
	}

	for _, v := range variants {
		r := build(v.opts)
		var dst []byte

		b.Run(v.name+"/miss", func(b *testing.B) {
			for i := 0; i < b.N; i++ {
				dst, _ = r.Append(dst[:0], uint64((i%n)*2+1)) // odd = absent
			}
		})
		b.Run(v.name+"/hit", func(b *testing.B) {
			for i := 0; i < b.N; i++ {
				dst, _ = r.Append(dst[:0], uint64((i%n)*2)) // even = present
			}
		})
	}
}