Basic Operations

Basic Operations

Basic operations for LotusDB.

Open a database

import (
	"github.com/flower-corp/lotusdb"
	"io/ioutil"
	"os"
)

func main() {
	// open a db with default options.
	path, _ := ioutil.TempDir("", "lotusdb")
	// you must specify a db path.
	opts := lotusdb.DefaultOptions(path)
	db, err := lotusdb.Open(opts)
	defer func() {
		_ = db.Close()
	}()

	if err != nil {
		panic(err)
	}
}

Opening a database is open the default Column Family, and you can set other options by opts.CfOpts.XXX.

Write

import (
   "github.com/flower-corp/lotusdb"
   "io/ioutil"
   "time"
)

func main() {
   path, _ := ioutil.TempDir("", "lotusdb")
   opts := lotusdb.DefaultOptions(path)
   db, err := lotusdb.Open(opts)
   if err != nil {
      panic(err)
   }
   defer db.Close()

   // 1.----put----
   key1 := []byte("name")
   err = db.Put(key1, []byte("lotusdb"))
   if err != nil {
      // ...
   }

   key2 := []byte("feature")
   // 2.----put with options----
   writeOpts := &lotusdb.WriteOptions{
      Sync:      true,
      ExpiredAt: time.Now().Add(time.Second * 100).Unix(),
   }
   err = db.PutWithOptions(key2, []byte("store data"), writeOpts)
   if err != nil {
      // ...
   }
}

Read

import (
   "github.com/flower-corp/lotusdb"
   "io/ioutil"
   "time"
)

func main() {
   path, _ := ioutil.TempDir("", "lotusdb")
   opts := lotusdb.DefaultOptions(path)
   db, err := lotusdb.Open(opts)
   if err != nil {
      panic(err)
   }
   defer db.Close()

   key1 := []byte("name")
   // 3.----get----
   val, err := db.Get(key1)
   if err != nil {
      // ...
   }
   if len(val) > 0 {
      // ...
   }
}

Delete

import (
   "github.com/flower-corp/lotusdb"
   "io/ioutil"
   "time"
)

func main() {
   path, _ := ioutil.TempDir("", "lotusdb")
   opts := lotusdb.DefaultOptions(path)
   db, err := lotusdb.Open(opts)
   if err != nil {
      panic(err)
   }
   defer db.Close()

   key1 := []byte("name")
   // 4.----delete----
   err = db.Delete(key1)
   if err != nil {
      // ...
   }

   // 5.----delete with options----
   deleteOpts := &lotusdb.WriteOptions{
      Sync:       false,
      DisableWal: true,
   }
   err = db.DeleteWithOptions([]byte("dummy key"), deleteOpts)
   if err != nil {
      // ...
   }
}

Column Family

ColumnFamily is a namespace of keys and values, each key-value pair in LotusDB is associated with exactly one Column Family.

If no Column Family is specified, key/value pair is associated with Column Family "cf_default".

Column Families provide a way to logically partition the database.

import (
   "github.com/flower-corp/lotusdb"
   "io/ioutil"
)

func main() {
   // open a db with default options.
   path, _ := ioutil.TempDir("", "lotusdb")
   // you must specify a db path.
   opts := lotusdb.DefaultOptions(path)
   db, err := lotusdb.Open(opts)
   defer func() {
      _ = db.Close()
   }()
   if err != nil {
      panic(err)
   }

   cfOpts := lotusdb.DefaultColumnFamilyOptions("a-new-cf")
   cfOpts.DirPath = "/tmp"
   cf, err := db.OpenColumnFamily(cfOpts)
   if err != nil {
      panic(err)
   }
   err = cf.Put([]byte("name"), []byte("LotusDB"))
   if err != nil {
      // ...
   }
}