How Can I Efficiently Serialize Go Structs to Disk and Minimize File Size?

Efficient Go Serialization of Struct to Disk

Problem:

Optimizing serialization performance by minimizing bloat in the output when encoding structs to disk using gob.

Proposed Solution:

While the gob package provides efficient serialization, it includes type information in the encoding, resulting in an initial overhead of 26 bytes per unique type. For structures with multiple instances, this overhead can be amortized across them.

Alternative:

For applications where even this overhead is unacceptable, consider using compression techniques like flate, zlib, gzip, or bzip2 to further reduce the output size by 50-80%.

Example:

The following code demonstrates the overhead of a single Entry using gob:

package main

import (
    "bytes"
    "encoding/gob"
    "fmt"
)

type Entry struct {
    Key string
    Val string
}

func main() {
    var buf bytes.Buffer
    enc := gob.NewEncoder(&buf)
    e := Entry{"k1", "v1"}
    enc.Encode(e)
    fmt.Println(buf.Len()) // Prints 48 bytes
}

If multiple instances of Entry are serialized, the overhead is amortized:

for i := 0; i < 1000; i++ {
    e.Key = fmt.Sprintf("k%3d", i)
    e.Val = fmt.Sprintf("v%3d", i)
    enc.Encode(e)
}
fmt.Println(buf.Len()) // Prints 16036 bytes = 16.04 bytes/Entry

To achieve the desired compact serialization format, additional compression techniques can be used:

import (
    "compress/bzip2"
    "compress/flate"
    "compress/gzip"
    "compress/zlib"
)

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)
}

The resulting output sizes with compression techniques:

Technique	Output Size	Average / Entry
Naked	16036 bytes	16.04 bytes
flate	4120 bytes	4.12 bytes
zlib	4126 bytes	4.13 bytes
gzip	4138 bytes	4.14 bytes
bzip2	2042 bytes	2.04 bytes

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