goleveldb Documentation

Install the leveldb package using go get:

go get github.com/syndtr/goleveldb/leveldb

To start an iteration from a specific key, use iter.Seek(key). This is useful for range scans starting at a known point.

iter := db.NewIterator(nil, nil)
for ok := iter.Seek(key); ok; ok = iter.Next() {
	// Use key/value.
	...
}
iter.Release()
err = iter.Error()
...

Use db.NewIterator to traverse the database.

Important:

• The slices returned by iter.Key() and iter.Value() are only valid until the next call to Next(). Do not modify them or store them without copying.
• Always call iter.Release() to free resources.
• Check iter.Error() after the loop to ensure no errors occurred during iteration.

iter := db.NewIterator(nil, nil)
for iter.Next() {
	// Remember that the contents of the returned slice should not be modified,
	// and only valid until the next call to Next.
	key := iter.Key()
	value := iter.Value()
	...
}
iter.Release()
err = iter.Error()
...

You can limit the scope of an iterator using util.Range or util.BytesPrefix.

Range Scan: Use &util.Range{Start: []byte("..."), Limit: []byte("...")} to iterate between two keys.

Prefix Scan: Use util.BytesPrefix([]byte("...")) to iterate over all keys starting with a specific prefix.

// Iterate over subset of database content
iter := db.NewIterator(&util.Range{Start: []byte("foo"), Limit: []byte("xoo")}, nil)
for iter.Next() {
	// Use key/value
	...
}
iter.Release()
err = iter.Error()
...

// Iterate over subset of database content with a particular prefix
iter := db.NewIterator(util.BytesPrefix([]byte("foo-")), nil)
for iter.Next() {
	// Use key/value
	...
}
iter.Release()
err = iter.Error()
...

Use leveldb.OpenFile to open an existing database or create a new one at the specified path. The returned *leveldb.DB instance is safe for concurrent use by multiple goroutines. Always ensure you call db.Close() when finished.

// The returned DB instance is safe for concurrent use. Which mean that all
// DB's methods may be called concurrently from multiple goroutine.
db, err := leveldb.OpenFile("path/to/db", nil)
...
defer db.Close()
...

To improve read performance, you can enable a Bloom filter by passing an opt.Options struct to leveldb.OpenFile.

o := &opt.Options{
	Filter: filter.NewBloomFilter(10),
}
db, err := leveldb.OpenFile("path/to/db", o)
...
defer db.Close()
...

Use leveldb.Batch to group multiple Put and Delete operations into a single atomic write using db.Write(batch, nil). This is more efficient than multiple individual writes.

batch := new(leveldb.Batch)
batch.Put([]byte("foo"), []byte("value"))
batch.Put([]byte("bar"), []byte("another value"))
batch.Delete([]byte("baz"))
err = db.Write(batch, nil)
...

Perform basic key-value operations using Get, Put, and Delete.

Note: The byte slice returned by Get should not be modified, as it points to internal buffers.

// Remember that the contents of the returned slice should not be modified.
data, err := db.Get([]byte("key"), nil)
...
err = db.Put([]byte("key"), []byte("value"), nil)
...
err = db.Delete([]byte("key"), nil)
...