How Can I Efficiently Serialize Go Structs to Disk with Minimal File Size?

Efficient Go Serialization of Struct to Disk: Achieving Minimal Bloat

Despite the bloated output produced by gob serialization, a deeper analysis reveals that subsequent entries of the same type incur only a 12-byte overhead. This overhead represents the minimum size required to encode two strings of length 4 bytes (including length prefixes).

To reduce the overall file size, consider the following strategies:

• Use Multiple Encoder Instances: Amortizing the compilation cost of the custom codec across multiple encoders can significantly reduce the overhead for the first entry.
• Compress the Output: Using compression libraries like compress/flate or bzip2 can further reduce the file size, with bzip2 achieving the highest efficiency in the provided test (2.04 bytes/Entry).

Code Demonstration:

The following Go code demonstrates the various approaches discussed:

package main

import (
    "bytes"
    "compress/bzip2"
    "compress/flate"
    "compress/gzip"
    "compress/zlib"
    "encoding/gob"
    "fmt"
    "io"
)

type Entry struct {
    Key string
    Val string
}

func main() {
    // Create test data
    entries := make([]Entry, 1000)
    for i := 0; i < 1000; i++ {
        entries[i].Key = fmt.Sprintf("k%03d", i)
        entries[i].Val = fmt.Sprintf("v%03d", i)
    }

    // Test different encoding/compression techniques
    for _, name := range []string{"Naked", "flate", "zlib", "gzip", "bzip2"} {
        buf := &bytes.Buffer{}

        var out io.Writer
        switch name {
        case "Naked":
            out = buf
        case "flate":
            out, _ = flate.NewWriter(buf, flate.DefaultCompression)
        case "zlib":
            out, _ = zlib.NewWriterLevel(buf, zlib.DefaultCompression)
        case "gzip":
            out = gzip.NewWriter(buf)
        case "bzip2":
            out, _ = bzip2.NewWriter(buf, nil)
        }

        enc := gob.NewEncoder(out)
        for _, e := range entries {
            enc.Encode(e)
        }

        if c, ok := out.(io.Closer); ok {
            c.Close()
        }
        fmt.Printf("[%5s] Length: %5d, average: %5.2f / Entry\n",
            name, buf.Len(), float64(buf.Len())/1000)
    }
}

Output:

[Naked] Length: 16053, average: 16.05 / Entry
[flate] Length:  3988, average:  3.99 / Entry
[ zlib] Length:  3994, average:  3.99 / Entry
[ gzip] Length:  4006, average:  4.01 / Entry
[bzip2] Length:  1977, average:  1.98 / Entry

As evident from the output, using compression techniques significantly reduces the file size, with bzip2 achieving an impressive 1.98 bytes/Entry.

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