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NutsDB is a simple, fast, embeddable and persistent key/value store written in pure Go.
It supports fully serializable transactions and many data structures such as list、set、sorted set. All operations happen inside a Tx. Tx represents a transaction, which can be read-only or read-write. Read-only transactions can read values for a given bucket and given key or iterate over a set of key-value pairs. Read-write transactions can update and delete keys from the DB.
This project is still in the experimental stage and has not passed the test of the actual production environment. Welcome to issue and contribute
I wanted a simple, fast, embeddable and persistent key/value store written in pure Go. There are some options:
BoltDB,it is based on B+ tree, has a good random read performance and awesome sequential scan performance, and it supports ACID transactions with serializable isolation, but it is terrible at random write performance.
GoLevelDB is based on a log-structured merge-tree (LSM tree), but it not supports transactions.
Badger is based on LSM tree with value log. It designed for SSDs. It also supports transactions. But its write performance is not as good as i thought.
So i tried to build a kv store by myself, i wanted to find a simple store engine model as reference. Finally i found the bitcask model. It is very simple and easy to implement. Howerver it has its limition,like range or prefix queries are not effcient. For example, you can not easily scan over all keys between user000000 and user999999, you had to look up each key individully in the hashmap.
In order to break the limition, i tried to optimize them. I tried to use B+ tree replace of hashmap and use mmap to optimize write performance. Finally i did it and named NutsDB. NutsDB offers a high read/write performance and supports transactions. And it still has a lot of room for optimization. Welcome contributions to NutsDB.
- Getting Started
- Using Other data structures
- Comparison with other databases
- Benchmarks
- Caveats & Limitations
- Contact
- Contributing
- Acknowledgements
- License
To start using NutsDB, first needs Go installed (version 1.11+ is required). and run go get:
go get -u github.com/xujiajun/nutsdb
To open your database, use the nutsdb.Open() function,with the appropriate options.The Dir , EntryIdxMode and SegmentSize options are must be specified by the client.
package main
import (
"log"
"github.com/xujiajun/nutsdb"
)
func main() {
// Open the database located in the /tmp/nutsdb directory.
// It will be created if it doesn't exist.
opt := nutsdb.DefaultOptions
opt.Dir = "/tmp/nutsdb"
db, err := nutsdb.Open(opt)
if err != nil {
log.Fatal(err)
}
defer db.Close()
...
}NutsDB allows only one read-write transaction at a time but allows as many read-only transactions as you want at a time. Each transaction has a consistent view of the data as it existed when the transaction started.
When a transaction fails, it will roll back, and revert all changes that occurred to the database during that transaction. When a read/write transaction succeeds all changes are persisted to disk.
Creating transaction from the DB is thread safe.
err := db.Update(
func(tx *nutsdb.Tx) error {
...
return nil
})err := db.View(
func(tx *nutsdb.Tx) error {
...
return nil
})The DB.View() and DB.Update() functions are wrappers around the DB.Begin() function. These helper functions will start the transaction, execute a function, and then safely close your transaction if an error is returned. This is the recommended way to use NutsDB transactions.
However, sometimes you may want to manually start and end your transactions. You can use the DB.Begin() function directly but please be sure to close the transaction.
// Start a write transaction.
tx, err := db.Begin(true)
if err != nil {
return err
}
bucket := "bucket1"
key := []byte("foo")
val := []byte("bar")
// Use the transaction.
if err = tx.Put(bucket, key, val, Persistent); err != nil {
// Rollback the transaction.
tx.Rollback()
} else {
// Commit the transaction and check for error.
if err = tx.Commit(); err != nil {
tx.Rollback()
return err
}
}Buckets are collections of key/value pairs within the database. All keys in a bucket must be unique. Bucket can be interpreted as a table or namespace. So you can store the same key in different bucket.
key := []byte("key001")
val := []byte("val001")
bucket001 := "bucket001"
if err := db.Update(
func(tx *nutsdb.Tx) error {
if err := tx.Put(bucket001, key, val, 0); err != nil {
return err
}
return nil
}); err != nil {
log.Fatal(err)
}
bucket002 := "bucket002"
if err := db.Update(
func(tx *nutsdb.Tx) error {
if err := tx.Put(bucket002, key, val, 0); err != nil {
return err
}
return nil
}); err != nil {
log.Fatal(err)
}To save a key/value pair to a bucket, use the tx.Put method:
if err := db.Update(
func(tx *nutsdb.Tx) error {
key := []byte("name1")
val := []byte("val1")
bucket: = "bucket1"
if err := tx.Put(bucket, key, val, 0); err != nil {
return err
}
return nil
}); err != nil {
log.Fatal(err)
}This will set the value of the "name1" key to "val1" in the bucket1 bucket.
To update the the value of the "name1" key,we can still use the tx.Put function:
if err := db.Update(
func(tx *nutsdb.Tx) error {
key := []byte("name1")
val := []byte("val1-modify") // Update the value
bucket: = "bucket1"
if err := tx.Put(bucket, key, val, 0); err != nil {
return err
}
return nil
}); err != nil {
log.Fatal(err)
}To retrieve this value, we can use the tx.Get function:
if err := db.View(
func(tx *nutsdb.Tx) error {
key := []byte("name1")
bucket: = "bucket1"
if e, err := tx.Get(bucket, key); err != nil {
return err
} else {
fmt.Println(string(e.Value)) // "val1-modify"
}
return nil
}); err != nil {
log.Println(err)
}Use the tx.Delete() function to delete a key from the bucket.
if err := db.Update(
func(tx *nutsdb.Tx) error {
key := []byte("name1")
bucket: = "bucket1"
if err := tx.Delete(bucket, key); err != nil {
return err
}
return nil
}); err != nil {
log.Fatal(err)
}NusDB supports TTL(Time to Live) for keys, you can use tx.Put function with a ttl parameter.
if err := db.Update(
func(tx *nutsdb.Tx) error {
key := []byte("name1")
val := []byte("val1")
bucket: = "bucket1"
// If set ttl = 0 or Persistent, this key will nerver expired.
// Set ttl = 60 , after 60 seconds, this key will expired.
if err := tx.Put(bucket, key, val, 60); err != nil {
return err
}
return nil
}); err != nil {
log.Fatal(err)
}NutsDB stores its keys in byte-sorted order within a bucket. This makes sequential iteration over these keys extremely fast.
To iterate over a key prefix, we can use PrefixScan function, and the paramter limitNum constrain the number of entries returned :
if err := db.View(
func(tx *nutsdb.Tx) error {
prefix := []byte("user_")
// Constrain 100 entries returned
if entries, err := tx.PrefixScan(bucket, prefix, 100); err != nil {
return err
} else {
keys, es := nutsdb.SortedEntryKeys(entries)
for _, key := range keys {
fmt.Println(key, string(es[key].Value))
}
}
return nil
}); err != nil {
log.Fatal(err)
}To scan over a range, we can use RangeScan function. For example：
if err := db.View(
func(tx *nutsdb.Tx) error {
// Assume key from user_0000000 to user_9999999.
// Query a specific user key range like this.
start := []byte("user_0010001")
end := []byte("user_0010010")
bucket：= []byte("user_list")
if entries, err := tx.RangeScan(bucket, start, end); err != nil {
return err
} else {
keys, es := nutsdb.SortedEntryKeys(entries)
for _, key := range keys {
fmt.Println(key, string(es[key].Value))
}
}
return nil
}); err != nil {
log.Fatal(err)
}NutsDB supports merge operation. you can use db.Merge() function removes dirty data and reduce data redundancy. Call this function from a read-write transaction. It will effect other write request. So you can execute it at the appropriate time.
err := db.Merge()
if err != nil {
...
}NutsDB is easy to backup. You can use the db.Backup() function at given dir, call this function from a read-only transaction, it will perform a hot backup and not block your other database reads and writes.
err = db.Backup(dir)
if err != nil {
...
}The syntax here is modeled after Redis commands
Inserts the values at the tail of the list stored in the bucket at given bucket,key and values.
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "bucketForList"
key := []byte("myList")
val := []byte("val1")
return tx.RPush(bucket, key, val)
}); err != nil {
log.Fatal(err)
}Inserts the values at the head of the list stored in the bucket at given bucket,key and values.
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "bucketForList"
key := []byte("myList")
val := []byte("val2")
return tx.LPush(bucket, key, val)
}); err != nil {
log.Fatal(err)
}Removes and returns the first element of the list stored in the bucket at given bucket and key.
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "bucketForList"
key := []byte("myList")
if item, err := tx.LPop(bucket, key); err != nil {
return err
} else {
fmt.Println("LPop item:", string(item))
}
return nil
}); err != nil {
log.Fatal(err)
}Returns the first element of the list stored in the bucket at given bucket and key.
if err := db.View(
func(tx *nutsdb.Tx) error {
bucket := "bucketForList"
key := []byte("myList")
if item, err := tx.LPeek(bucket, key); err != nil {
return err
} else {
fmt.Println("LPeek item:", string(item)) //val11
}
return nil
}); err != nil {
log.Fatal(err)
}Removes and returns the last element of the list stored in the bucket at given bucket and key.
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "bucketForList"
key := []byte("myList")
if item, err := tx.RPop(bucket, key); err != nil {
return err
} else {
fmt.Println("RPop item:", string(item))
}
return nil
}); err != nil {
log.Fatal(err)
}Returns the last element of the list stored in the bucket at given bucket and key.
if err := db.View(
func(tx *nutsdb.Tx) error {
bucket := "bucketForList"
key := []byte("myList")
if item, err := tx.RPeek(bucket, key); err != nil {
return err
} else {
fmt.Println("RPeek item:", string(item))
}
return nil
}); err != nil {
log.Fatal(err)
}Returns the specified elements of the list stored in the bucket at given bucket,key, start and end. The offsets start and stop are zero-based indexes 0 being the first element of the list (the head of the list), 1 being the next element and so on. Start and end can also be negative numbers indicating offsets from the end of the list, where -1 is the last element of the list, -2 the penultimate element and so on.
if err := db.View(
func(tx *nutsdb.Tx) error {
bucket := "bucketForList"
key := []byte("myList")
if items, err := tx.LRange(bucket, key, 0, -1); err != nil {
return err
} else {
//fmt.Println(items)
for _, item := range items {
fmt.Println(string(item))
}
}
return nil
}); err != nil {
log.Fatal(err)
}Removes the first count occurrences of elements equal to value from the list stored in the bucket at given bucket,key,count. The count argument influences the operation in the following ways:
- count > 0: Remove elements equal to value moving from head to tail.
- count < 0: Remove elements equal to value moving from tail to head.
- count = 0: Remove all elements equal to value.
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "bucketForList"
key := []byte("myList")
return tx.LRem(bucket, key, 1)
}); err != nil {
log.Fatal(err)
}Sets the list element at index to value.
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "bucketForList"
key := []byte("myList")
if err := tx.LSet(bucket, key, 0, []byte("val11")); err != nil {
return err
} else {
fmt.Println("LSet ok, index 0 item value => val11")
}
return nil
}); err != nil {
log.Fatal(err)
}Trims an existing list so that it will contain only the specified range of elements specified. the offsets start and stop are zero-based indexes 0 being the first element of the list (the head of the list), 1 being the next element and so on.Start and end can also be negative numbers indicating offsets from the end of the list, where -1 is the last element of the list, -2 the penultimate element and so on.
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "bucketForList"
key := []byte("myList")
return tx.LTrim(bucket, key, 0, 1)
}); err != nil {
log.Fatal(err)
}Returns the size of key in the bucket in the bucket at given bucket and key.
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "bucketForList"
key := []byte("myList")
if size,err := tx.LSize(bucket, key); err != nil {
return err
} else {
fmt.Println("myList size is ",size)
}
return nil
}); err != nil {
log.Fatal(err)
}Adds the specified members to the set stored int the bucket at given bucket,key and items.
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "bucketForSet"
key := []byte("mySet")
return tx.SAdd(bucket, key, []byte("a"), []byte("b"), []byte("c"))
}); err != nil {
log.Fatal(err)
}Returns if the specified members are the member of the set int the bucket at given bucket,key and items.
if err := db.View(
func(tx *nutsdb.Tx) error {
bucket := "bucketForSet"
key := []byte("mySet")
if ok, err := tx.SAreMembers(bucket, key, []byte("a"), []byte("b"), []byte("c")); err != nil {
return err
} else {
fmt.Println("SAreMembers:", ok)
}
return nil
}); err != nil {
log.Fatal(err)
}Returns the set cardinality (number of elements) of the set stored in the bucket at given bucket and key.
if err := db.View(
func(tx *nutsdb.Tx) error {
bucket := "bucketForSet"
key := []byte("mySet")
if num, err := tx.SCard(bucket, key); err != nil {
return err
} else {
fmt.Println("SCard:", num)
}
return nil
}); err != nil {
log.Fatal(err)
}Returns the members of the set resulting from the difference between the first set and all the successive sets in one bucket.
key1 := []byte("mySet1")
key2 := []byte("mySet2")
bucket := "bucketForSet"
if err := db.Update(
func(tx *nutsdb.Tx) error {
return tx.SAdd(bucket, key1, []byte("a"), []byte("b"), []byte("c"))
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
return tx.SAdd(bucket, key2, []byte("c"), []byte("d"))
}); err != nil {
log.Fatal(err)
}
if err := db.View(
func(tx *nutsdb.Tx) error {
if items, err := tx.SDiffByOneBucket(bucket, key1, key2); err != nil {
return err
} else {
fmt.Println("SDiffByOneBucket:", items)
for _, item := range items {
fmt.Println("item", string(item))
}
//item a
//item b
}
return nil
}); err != nil {
log.Fatal(err)
}Returns the members of the set resulting from the difference between the first set and all the successive sets in two buckets.
bucket1 := "bucket1"
key1 := []byte("mySet1")
bucket2 := "bucket2"
key2 := []byte("mySet2")
if err := db.Update(
func(tx *nutsdb.Tx) error {
return tx.SAdd(bucket1, key1, []byte("a"), []byte("b"), []byte("c"))
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
return tx.SAdd(bucket2, key2, []byte("c"), []byte("d"))
}); err != nil {
log.Fatal(err)
}
if err := db.View(
func(tx *nutsdb.Tx) error {
if items, err := tx.SDiffByTwoBuckets(bucket1, key1, bucket2, key2); err != nil {
return err
} else {
fmt.Println("SDiffByTwoBuckets:", items)
for _, item := range items {
fmt.Println("item", string(item))
}
}
return nil
}); err != nil {
log.Fatal(err)
}Returns if the set in the bucket at given bucket and key.
bucket := "bucketForSet"
if err := db.View(
func(tx *nutsdb.Tx) error {
if ok, err := tx.SHasKey(bucket, []byte("mySet")); err != nil {
return err
} else {
fmt.Println("SHasKey", ok)
}
return nil
}); err != nil {
log.Fatal(err)
}Returns if member is a member of the set stored int the bucket at given bucket,key and item.
bucket := "bucketForSet"
if err := db.View(
func(tx *nutsdb.Tx) error {
if ok, err := tx.SIsMember(bucket, []byte("mySet"), []byte("a")); err != nil {
return err
} else {
fmt.Println("SIsMember", ok)
}
return nil
}); err != nil {
log.Fatal(err)
}Returns all the members of the set value stored int the bucket at given bucket and key.
bucket := "bucketForSet"
if err := db.View(
func(tx *nutsdb.Tx) error {
if items, err := tx.SMembers(bucket, []byte("mySet")); err != nil {
return err
} else {
fmt.Println("SMembers", items)
for _, item := range items {
fmt.Println("item", string(item))
}
}
return nil
}); err != nil {
log.Fatal(err)
}
Moves member from the set at source to the set at destination in one bucket.
bucket3 := "bucket3"
if err := db.Update(
func(tx *nutsdb.Tx) error {
return SAdd(bucket3, []byte("mySet1"), []byte("a"), []byte("b"), []byte("c"))
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
return tx.SAdd(bucket3, []byte("mySet2"), []byte("c"), []byte("d"), []byte("e"))
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
if ok, err := tx.SMoveByOneBucket(bucket3, []byte("mySet1"), []byte("mySet2"), []byte("a")); err != nil {
return err
} else {
fmt.Println("SMoveByOneBucket", ok)
}
return nil
}); err != nil {
log.Fatal(err)
}
if err := db.View(
func(tx *nutsdb.Tx) error {
if items, err := tx.SMembers(bucket3, []byte("mySet1")); err != nil {
return err
} else {
fmt.Println("after SMoveByOneBucket bucket3 mySet1 SMembers", items)
for _, item := range items {
fmt.Println("item", string(item))
}
}
return nil
}); err != nil {
log.Fatal(err)
}
if err := db.View(
func(tx *nutsdb.Tx) error {
if items, err := tx.SMembers(bucket3, []byte("mySet2")); err != nil {
return err
} else {
fmt.Println("after SMoveByOneBucket bucket3 mySet2 SMembers", items)
for _, item := range items {
fmt.Println("item", string(item))
}
}
return nil
}); err != nil {
log.Fatal(err)
}Moves member from the set at source to the set at destination in two buckets.
bucket4 := "bucket4"
bucket5 := "bucket5"
if err := db.Update(
func(tx *nutsdb.Tx) error {
return tx.SAdd(bucket4, []byte("mySet1"), []byte("a"), []byte("b"), []byte("c"))
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
return tx.SAdd(bucket5, []byte("mySet2"), []byte("c"), []byte("d"), []byte("e"))
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
if ok, err := tx.SMoveByTwoBuckets(bucket4, []byte("mySet1"), bucket5, []byte("mySet2"), []byte("a")); err != nil {
return err
} else {
fmt.Println("SMoveByTwoBuckets", ok)
}
return nil
}); err != nil {
log.Fatal(err)
}
if err := db.View(
func(tx *nutsdb.Tx) error {
if items, err := tx.SMembers(bucket4, []byte("mySet1")); err != nil {
return err
} else {
fmt.Println("after SMoveByTwoBuckets bucket4 mySet1 SMembers", items)
for _, item := range items {
fmt.Println("item", string(item))
}
}
return nil
}); err != nil {
log.Fatal(err)
}
if err := db.View(
func(tx *nutsdb.Tx) error {
if items, err := tx.SMembers(bucket5, []byte("mySet2")); err != nil {
return err
} else {
fmt.Println("after SMoveByTwoBuckets bucket5 mySet2 SMembers", items)
for _, item := range items {
fmt.Println("item", string(item))
}
}
return nil
}); err != nil {
log.Fatal(err)
}Removes and returns one or more random elements from the set value store in the bucket at given bucket and key.
if err := db.Update(
func(tx *nutsdb.Tx) error {
key := []byte("mySet")
if item, err := tx.SPop(bucket, key); err != nil {
return err
} else {
fmt.Println("SPop item from mySet:", string(item))
}
return nil
}); err != nil {
log.Fatal(err)
}Removes the specified members from the set stored int the bucket at given bucket,key and items.
bucket6:="bucket6"
if err := db.Update(
func(tx *nutsdb.Tx) error {
return tx.SAdd(bucket6, []byte("mySet"), []byte("a"), []byte("b"), []byte("c"))
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
if err := tx.SRem(bucket6, []byte("mySet"), []byte("a")); err != nil {
return err
} else {
fmt.Println("SRem ok")
}
return nil
}); err != nil {
log.Fatal(err)
}
if err := db.View(
func(tx *nutsdb.Tx) error {
if items, err := tx.SMembers(bucket6, []byte("mySet")); err != nil {
return err
} else {
fmt.Println("SMembers items:", items)
for _, item := range items {
fmt.Println("item:", string(item))
}
}
return nil
}); err != nil {
log.Fatal(err)
}The members of the set resulting from the union of all the given sets in one bucket.
bucket7 := "bucket1"
key1 := []byte("mySet1")
key2 := []byte("mySet2")
if err := db.Update(
func(tx *nutsdb.Tx) error {
return tx.SAdd(bucket7, key1, []byte("a"), []byte("b"), []byte("c"))
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
return tx.SAdd(bucket7, key2, []byte("c"), []byte("d"))
}); err != nil {
log.Fatal(err)
}
if err := db.View(
func(tx *nutsdb.Tx) error {
if items, err := tx.SUnionByOneBucket(bucket7, key1, key2); err != nil {
return err
} else {
fmt.Println("SUnionByOneBucket:", items)
for _, item := range items {
fmt.Println("item", string(item))
}
}
return nil
}); err != nil {
log.Fatal(err)
}The members of the set resulting from the union of all the given sets in two buckets.
bucket8 := "bucket1"
key1 := []byte("mySet1")
bucket9 := "bucket2"
key2 := []byte("mySet2")
if err := db.Update(
func(tx *nutsdb.Tx) error {
return tx.SAdd(bucket8, key1, []byte("a"), []byte("b"), []byte("c"))
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
return tx.SAdd(bucket9, key2, []byte("c"), []byte("d"))
}); err != nil {
log.Fatal(err)
}
if err := db.View(
func(tx *nutsdb.Tx) error {
if items, err := tx.SUnionByTwoBuckets(bucket8, key1, bucket9, key2); err != nil {
return err
} else {
fmt.Println("SUnionByTwoBucket:", items)
for _, item := range items {
fmt.Println("item", string(item))
}
}
return nil
}); err != nil {
log.Fatal(err)
}Adds the specified member with the specified score and the specified value to the sorted set stored at bucket.
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet1"
key := []byte("key1")
return tx.ZAdd(bucket, key, 1, []byte("val1"))
}); err != nil {
log.Fatal(err)
}Returns the sorted set cardinality (number of elements) of the sorted set stored at bucket.
if err := db.View(
func(tx *nutsdb.Tx) error {
bucket := "myZSet1"
if num, err := tx.ZCard(bucket); err != nil {
return err
} else {
fmt.Println("ZCard num", num)
}
return nil
}); err != nil {
log.Fatal(err)
}Returns the number of elements in the sorted set at bucket with a score between min and max and opts.
Opts includes the following parameters:
- Limit int // limit the max nodes to return
- ExcludeStart bool // exclude start value, so it search in interval (start, end] or (start, end)
- ExcludeEnd bool // exclude end value, so it search in interval [start, end) or (start, end)
if err := db.View(
func(tx *nutsdb.Tx) error {
bucket := "myZSet1"
if num, err := tx.ZCount(bucket, 0, 1, nil); err != nil {
return err
} else {
fmt.Println("ZCount num", num)
}
return nil
}); err != nil {
log.Fatal(err)
}Returns node in the bucket at given bucket and key.
if err := db.View(
func(tx *nutsdb.Tx) error {
bucket := "myZSet1"
key := []byte("key2")
if node, err := tx.ZGetByKey(bucket, key); err != nil {
return err
} else {
fmt.Println("ZGetByKey key2 val:", string(node.Value))
}
return nil
}); err != nil {
log.Fatal(err)
}Returns all the members of the set value stored at bucket.
if err := db.View(
func(tx *nutsdb.Tx) error {
bucket := "myZSet1"
if nodes, err := tx.ZMembers(bucket); err != nil {
return err
} else {
fmt.Println("ZMembers:", nodes)
for _, node := range nodes {
fmt.Println("member:", node.Key(), string(node.Value))
}
}
return nil
}); err != nil {
log.Fatal(err)
}Returns the member with the highest score in the sorted set stored at bucket.
if err := db.View(
func(tx *nutsdb.Tx) error {
bucket := "myZSet1"
if node, err := tx.ZPeekMax(bucket); err != nil {
return err
} else {
fmt.Println("ZPeekMax:", string(node.Value))
}
return nil
}); err != nil {
log.Fatal(err)
}Returns the member with lowest score in the sorted set stored at bucket.
if err := db.View(
func(tx *nutsdb.Tx) error {
bucket := "myZSet1"
if node, err := tx.ZPeekMin(bucket); err != nil {
return err
} else {
fmt.Println("ZPeekMin:", string(node.Value))
}
return nil
}); err != nil {
log.Fatal(err)
}Removes and returns the member with the highest score in the sorted set stored at bucket.
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet1"
if node, err := tx.ZPopMax(bucket); err != nil {
return err
} else {
fmt.Println("ZPopMax:", string(node.Value)) //val3
}
return nil
}); err != nil {
log.Fatal(err)
}Removes and returns the member with the lowest score in the sorted set stored at bucket.
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet1"
if node, err := tx.ZPopMin(bucket); err != nil {
return err
} else {
fmt.Println("ZPopMin:", string(node.Value)) //val1
}
return nil
}); err != nil {
log.Fatal(err)
}Returns all the elements in the sorted set in one bucket at bucket and key with a rank between start and end (including elements with rank equal to start or end).
// ZAdd add items
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet2"
key1 := []byte("key1")
return tx.ZAdd(bucket, key1, 1, []byte("val1"))
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet2"
key2 := []byte("key2")
return tx.ZAdd(bucket, key2, 2, []byte("val2"))
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet2"
key3 := []byte("key3")
return tx.ZAdd(bucket, key3, 3, []byte("val3"))
}); err != nil {
log.Fatal(err)
}
// ZRangeByRank
if err := db.View(
func(tx *nutsdb.Tx) error {
bucket := "myZSet2"
if nodes, err := tx.ZRangeByRank(bucket, 1, 2); err != nil {
return err
} else {
fmt.Println("ZRangeByRank nodes :", nodes)
for _, node := range nodes {
fmt.Println("item:", node.Key(), node.Score())
}
//item: key1 1
//item: key2 2
}
return nil
}); err != nil {
log.Fatal(err)
}Returns all the elements in the sorted set at key with a score between min and max.
And the parameter Opts is the same as ZCount's.
// ZAdd
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet3"
key1 := []byte("key1")
return tx.ZAdd(bucket, key1, 70, []byte("val1"))
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet3"
key2 := []byte("key2")
return tx.ZAdd(bucket, key2, 90, []byte("val2"))
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet3"
key3 := []byte("key3")
return tx.ZAdd(bucket, key3, 86, []byte("val3"))
}); err != nil {
log.Fatal(err)
}
// ZRangeByScore
if err := db.View(
func(tx *nutsdb.Tx) error {
bucket := "myZSet3"
if nodes, err := tx.ZRangeByScore(bucket, 80, 100,nil); err != nil {
return err
} else {
fmt.Println("ZRangeByScore nodes :", nodes)
for _, node := range nodes {
fmt.Println("item:", node.Key(), node.Score())
}
//item: key3 86
//item: key2 90
}
return nil
}); err != nil {
log.Fatal(err)
} Returns the rank of member in the sorted set stored in the bucket at given bucket and key, with the scores ordered from low to high.
// ZAdd
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet4"
key1 := []byte("key1")
return tx.ZAdd(bucket, key1, 70, []byte("val1"))
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet4"
key2 := []byte("key2")
return tx.ZAdd(bucket, key2, 90, []byte("val2"))
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet4"
key3 := []byte("key3")
return tx.ZAdd(bucket, key3, 86, []byte("val3"))
}); err != nil {
log.Fatal(err)
}
// ZRank
if err := db.View(
func(tx *nutsdb.Tx) error {
bucket := "myZSet4"
key1 := []byte("key1")
if rank, err := tx.ZRank(bucket, key1); err != nil {
return err
} else {
fmt.Println("key1 ZRank :", rank) // key1 ZRank : 1
}
return nil
}); err != nil {
log.Fatal(err)
}Returns the rank of member in the sorted set stored in the bucket at given bucket and key,with the scores ordered from high to low.
// ZAdd
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet8"
key1 := []byte("key1")
return tx.ZAdd(bucket, key1, 10, []byte("val1"))
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet8"
key2 := []byte("key2")
return tx.ZAdd(bucket, key2, 20, []byte("val2"))
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet8"
key3 := []byte("key3")
return tx.ZAdd(bucket, key3, 30, []byte("val3"))
}); err != nil {
log.Fatal(err)
}
// ZRevRank
if err := db.View(
func(tx *nutsdb.Tx) error {
bucket := "myZSet8"
if rank, err := tx.ZRevRank(bucket, []byte("key3")); err != nil {
return err
} else {
fmt.Println("ZRevRank key1 rank:", rank) //ZRevRank key3 rank: 1
}
return nil
}); err != nil {
log.Fatal(err)
}Removes the specified members from the sorted set stored in one bucket at given bucket and key.
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet5"
key1 := []byte("key1")
return tx.ZAdd(bucket, key1, 10, []byte("val1"))
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet5"
key2 := []byte("key2")
return tx.ZAdd(bucket, key2, 20, []byte("val2"))
}); err != nil {
log.Fatal(err)
}
if err := db.View(
func(tx *nutsdb.Tx) error {
bucket := "myZSet5"
if nodes,err := tx.ZMembers(bucket); err != nil {
return err
} else {
fmt.Println("before ZRem key1, ZMembers nodes",nodes)
for _,node:=range nodes {
fmt.Println("item:",node.Key(),node.Score())
}
}
// before ZRem key1, ZMembers nodes map[key1:0xc00008cfa0 key2:0xc00008d090]
// item: key1 10
// item: key2 20
return nil
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet5"
if err := tx.ZRem(bucket, "key1"); err != nil {
return err
}
return nil
}); err != nil {
log.Fatal(err)
}
if err := db.View(
func(tx *nutsdb.Tx) error {
bucket := "myZSet5"
if nodes,err := tx.ZMembers(bucket); err != nil {
return err
} else {
fmt.Println("after ZRem key1, ZMembers nodes",nodes)
for _,node:=range nodes {
fmt.Println("item:",node.Key(),node.Score())
}
// after ZRem key1, ZMembers nodes map[key2:0xc00008d090]
// item: key2 20
}
return nil
}); err != nil {
log.Fatal(err)
}Removes all elements in the sorted set stored in one bucket at given bucket with rank between start and end. The rank is 1-based integer. Rank 1 means the first node; Rank -1 means the last node.
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet6"
key1 := []byte("key1")
return tx.ZAdd(bucket, key1, 10, []byte("val1"))
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet6"
key2 := []byte("key2")
return tx.ZAdd(bucket, key2, 20, []byte("val2"))
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet6"
key3 := []byte("key3")
return tx.ZAdd(bucket, key3, 30, []byte("val2"))
}); err != nil {
log.Fatal(err)
}
if err := db.View(
func(tx *nutsdb.Tx) error {
bucket := "myZSet6"
if nodes,err := tx.ZMembers(bucket); err != nil {
return err
} else {
fmt.Println("before ZRemRangeByRank, ZMembers nodes",nodes)
for _,node:=range nodes {
fmt.Println("item:",node.Key(),node.Score())
}
// before ZRemRangeByRank, ZMembers nodes map[key3:0xc00008d450 key1:0xc00008d270 key2:0xc00008d360]
// item: key1 10
// item: key2 20
// item: key3 30
}
return nil
}); err != nil {
log.Fatal(err)
}
if err := db.Update(
func(tx *nutsdb.Tx) error {
bucket := "myZSet6"
if err := tx.ZRemRangeByRank(bucket, 1,2); err != nil {
return err
}
return nil
}); err != nil {
log.Fatal(err)
}
if err := db.View(
func(tx *nutsdb.Tx) error {
bucket := "myZSet6"
if nodes,err := tx.ZMembers(bucket); err != nil {
return err
} else {
fmt.Println("after ZRemRangeByRank, ZMembers nodes",nodes)
for _,node:=range nodes {
fmt.Println("item:",node.Key(),node.Score())
}
// after ZRemRangeByRank, ZMembers nodes map[key3:0xc00008d450]
// item: key3 30
// key1 ZScore 10
}
return nil
}); err != nil {
log.Fatal(err)
}Returns the score of member in the sorted set in the bucket at given bucket and key.
if err := db.View(
func(tx *nutsdb.Tx) error {
bucket := "myZSet7"
if score,err := tx.ZScore(bucket, []byte("key1")); err != nil {
return err
} else {
fmt.Println("ZScore key1 score:",score)
}
return nil
}); err != nil {
log.Fatal(err)
}BoltDB is similar to NutsDB, both use B+tree and support transaction. However, Bolt uses a B+tree internally and only a single file, and NutsDB is based on bitcask model with multiple log files. NutsDB supports TTL and many data structures, but BoltDB not supports them .
LevelDB and RocksDB are based on a log-structured merge-tree (LSM tree).An LSM tree optimizes random writes by using a write ahead log and multi-tiered, sorted files called SSTables. LevelDB does not have transactions. It supports batch writing of key/values pairs and it supports read snapshots but it will not give you the ability to do a compare-and-swap operation safely. NutsDB supports many data structures, but they not support them.
Badger is based in LSM tree with value log. It designed for SSDs. It also supports transaction and TTL. But in my benchmark its write performance is not as good as i thought. In addition, NutsDB supports data structures such as list、set、sorted set, but Badger not supports them.
TODO
NutsDB supports two modes about entry index: HintAndRAMIdxMode and HintAndMemoryMapIdxMode. The default mode use HintAndRAMIdxMode, entries are indexed base on RAM, so its read/write performance is fast. but can’t handle databases much larger than the available physical RAM. If you set the HintAndMemoryMapIdxMode mode, HintIndex will not cache the value of the entry. Its write performance is also fast. To retrieve a key by seeking to offset relative to the start of the data file, so its read performance more slowly that RAM way, but it can handle databases much larger than the available physical RAM. And other data structures such as list, set, sorted set only supported with mode HintAndRAMIdxMode.
NutsDB will truncate data file if the active file is larger than SegmentSize, so the size of an entry can not be set larger than SegmentSize , defalut SegmentSize is 8MB, you can set it(opt.SegmentSize) as option before DB opening. Once set, it cannot be changed.
NutsDB currently works on Mac OS X and Linux. Windows not been tested.It may be does't work on windows.
thanks @damnever submit the issue about the ACID transactions.
In the nutsdb , a transaction presents a unit of work be performed.
The current version of nutsdb not promise data persistence， to provide high performance, there is no real time to do the sync operation, depends on the kernel to write, you can understand as a buffer, which is an optimistic operation, the kernel will be responsible for the "dirty" data will be written back to disk, but this point in time, the application not sure when to sync, when accumulated to a certain amount（segment size）for a munmap operation, will make the update data. This approach does not satisfy the D (persistence) nature. Later versions will provide a strongly synchronized policy.
More waiting to be added.
See CONTRIBUTING for details on submitting patches and the contribution workflow.
This package is inspired by the following:
The NutsDB is open-sourced software licensed under the Apache 2.0 license.