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use-buckets.md

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How to use buckets

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 {
    // you should call Bucket with data structure and the name of bucket first
    return tx.NewBucket(nutsdb.DataStructureBTree, bucket001)
}); err != nil {
    log.Fatal(err)
}

if err := db.Update(func(tx *nutsdb.Tx) error {
    return tx.Put(bucket001, key, val, 0)
}); err != nil {
    log.Fatal(err)
}

Also, this bucket is related to the data structure you use. Different data index structures that use the same bucket are also different. For example, you define a bucket named bucket_foo, so you need to use the list data structure, use tx.RPush to add data, you must query or retrieve from this bucket_foo data structure, use tx.RPop, tx.LRange, etc. You cannot use tx.Get (same index type as tx.GetAll, tx.Put, tx.Delete, tx.RangeScan, etc.) to read the data in this bucket_foo, because the index structure is different. Other data structures such as Set, Sorted Set are the same.

Iterate

IterateBuckets iterates over all the buckets that match the pattern. IterateBuckets function has three parameters: ds, pattern and function f.

The current version of the Iterate Buckets method supports the following EntryId Modes:

  • HintKeyValAndRAMIdxMode：represents ram index (key and value) mode.
  • HintKeyAndRAMIdxMode：represents ram index (only key) mode.

The pattern added in version 0.11.0 (represents the pattern to match):

  • pattern syntax refer to: filepath.Match

The current version of ds (represents the data structure):

  • DataStructureSet
  • DataStructureSortedSet
  • DataStructureBTree
  • DataStructureList
if err := db.View(
    func(tx *nutsdb.Tx) error {
        return tx.IterateBuckets(nutsdb.DataStructureBTree, "*", func(bucket string) bool {
            fmt.Println("bucket: ", bucket)
            // true: continue, false: break
            return true
        })
    }); err != nil {
    log.Fatal(err)
}

Delete

DeleteBucket represents delete bucket. DeleteBucket function has two parameters: ds(represents the data structure) and bucket.

The current version of the Iterate Buckets method supports the following EntryId Modes:

  • HintKeyValAndRAMIdxMode：represents ram index (key and value) mode.
  • HintKeyAndRAMIdxMode：represents ram index (only key) mode.

The current version of ds (represents the data structure)：

  • DataStructureSet
  • DataStructureSortedSet
  • DataStructureBTree
  • DataStructureList
if err := db.Update(
    func(tx *nutsdb.Tx) error {
        return tx.DeleteBucket(nutsdb.DataStructureBTree, bucket)
    }); err != nil {
    log.Fatal(err)
}