disktable

Overview ¶

Package disktable provides a write-once, read-many table with index supoprt. This is build on top of badgerDB, which is basically a key/value SSTable storage mechanism.

Let's create a table with some data:

dir := filepath.Join(os.TempDir(), "your_table"")
// Remove it if exists, may or may not want to do this. However you cannot
// create a table on a directory that exists.
os.RemoveAll(dir)

// These are our indexes on the data. AllowDuplicates allows duplicate entries
// in the index.
indexes := NewIndexes(
	&Index{Name: "First Name", AllowDuplicates: true},
	&Index{Name: "Last Name", AllowDuplicates: true},
	&Index{Name: "ID"},
}

w, err := New(dir, WithIndexes(indexes))
if err != nil {
	panic(err)
}

for _, data := range someData {
	b, err := proto.Marshal(data)
	if err != nil {
		panic(err)
	}

	insert := indexes.Insert(b).AddIndexKey(
		"First Name", UnsafeGetBytes(data.First),
	).AddIndexKey(
		"Last Name", UnsafeGetBytes(data.Last),
	).AddIndexKey(
		"ID", NumToByte(data.ID),
	)

	if err = w.WriteData(insert); err != nil {
		panic(err)
	}
}

if err := w.Close(); err != nil {
	panic(err)
}

Now let's open it and stream all records:

table, err := Open(dir)
if err != nil {
	panic(err)
}

results, err := table.FetchAll(ctx)
if err != nil {
	panic(err)
}

for result := range results {
	if result.Err != nil {
		panic(err)
	}

	entry := &pb.MyData{}
	if err := proto.Unmarshal(entry, result.Value); err != nil {
		panic(err)
	}

	fmt.Println("found: ", pretty.Sprint(entry))
}

Let's look for all entries that have the first name John:

results, err := table.Fetch(
	ctx,
	Lookup{IndexName: "First Name", Key: UnsafeGetBytes("John")},
)

if err != nil {
	panic(err)
}

for result := range results {
	if result.Err != nil {
		panic(err)
	}

	entry := &pb.MyData{}
	if err := proto.Unmarshal(entry, result.Value); err != nil {
		panic(err)
	}

	fmt.Println("found: ", pretty.Sprint(entry))
}