GODRIVER-3455 Make BSON benchmarks more representative of real use cases.

[matthewdale]

GODRIVER-3455

Summary

• Make BenchmarkMarshal and BenchmarkUnmarshal BSON benchmarks parallel.
• Add more test cases to BenchmarkMarshal and BenchmarkUnmarshal.
• Make it easier to run encoding-specific benchmarks (e.g. BSON, ExtJSON, etc) by restructuring the subtests to make the encoding the top-level subtest.

Background & Motivation

[mongodb-drivers-pr-bot]

API Change Report

No changes found!

[prestonvasquez]

I think "simple struct" reads better:

BenchmarkUnmarshal/simple_struct

[prestonvasquez]

I don't think this will report anything for the test cases, suggest moving b.ReportAllocs() to the inner-most subtest:

b.Run(tc.desc, func(b *testing.B) {
	b.ReportAllocs()
	b.RunParallel(func(pb *testing.PB) {
		for pb.Next() {
			_, err := Marshal(tc.value)
			if err != nil {
				b.Errorf("error marshalling BSON: %s", err)
			}
		}
	})
})

Same for BenchmarkUnmarshal

[prestonvasquez]

This case doesn't seem like it will be any different than encodetestInstance. But if we keep it, suggest defining it globally and adding it to BenchmarkUnmarshal as well.

[prestonvasquez]

Consider an alternative pattern for the test cases which will help avoid having to write out similar cases repeatedly. This also allows us to pre-compute the file reads.

deepBSON := readExtJSONFile("deep_bson.json.gz")
flatBSON := readExtJSONFile("flat_bson.json.gz")
fullBSON := readExtJSONFile("full_bson.json.gz")

inputs := []struct {
	name  string
	value any
}{
	{"simple", encodetestInstance},
	{"nested", nestedInstance},
	{"deep_bson.json.gz", deepBSON},
	{"flat_bson.json.gz", flatBSON},
	{"full_bson.json.gz", fullBSON},
}

destinations := []struct {
	name string
	dst  func() any
}{
	{"to struct", func() any { return &encodetest{} }},
	{"to map", func() any { return &map[string]any{} }},
	{"to D", func() any { return &D{} }},
}

var cases []struct {
	desc  string
	value any
	dst   func() any
}

for _, input := range inputs {
	for _, dest := range destinations {
		cases = append(cases, struct {
			desc  string
			value any
			dst   func() any
		}{
			desc:  input.name + " " + dest.name,
			value: input.value,
			dst:   dest.dst,
		})
	}
}