/
binary_search_tree_map.go
260 lines (217 loc) · 5.57 KB
/
binary_search_tree_map.go
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// _ _
// __ _____ __ ___ ___ __ _| |_ ___
// \ \ /\ / / _ \/ _` \ \ / / |/ _` | __/ _ \
// \ V V / __/ (_| |\ V /| | (_| | || __/
// \_/\_/ \___|\__,_| \_/ |_|\__,_|\__\___|
//
// Copyright © 2016 - 2024 Weaviate B.V. All rights reserved.
//
// CONTACT: hello@weaviate.io
//
package lsmkv
import (
"bytes"
"sort"
"github.com/weaviate/weaviate/adapters/repos/db/lsmkv/rbtree"
"github.com/weaviate/weaviate/entities/lsmkv"
)
type binarySearchTreeMap struct {
root *binarySearchNodeMap
}
func (t *binarySearchTreeMap) insert(key []byte, pair MapPair) {
if t.root == nil {
t.root = &binarySearchNodeMap{
key: key,
values: []MapPair{pair},
colourIsRed: false, // root node is always black
}
return
}
if newRoot := t.root.insert(key, pair); newRoot != nil {
t.root = newRoot
}
t.root.colourIsRed = false // Can be flipped in the process of balancing, but root is always black
}
func (t *binarySearchTreeMap) get(key []byte) ([]MapPair, error) {
if t.root == nil {
return nil, lsmkv.NotFound
}
return t.root.get(key)
}
func (t *binarySearchTreeMap) flattenInOrder() []*binarySearchNodeMap {
if t.root == nil {
return nil
}
return t.root.flattenInOrder()
}
type binarySearchNodeMap struct {
key []byte
values []MapPair
left *binarySearchNodeMap
right *binarySearchNodeMap
parent *binarySearchNodeMap
colourIsRed bool
}
func (n *binarySearchNodeMap) Parent() rbtree.Node {
if n == nil {
return nil
}
return n.parent
}
func (n *binarySearchNodeMap) SetParent(parent rbtree.Node) {
if n == nil {
addNewSearchNodeMapReceiver(&n)
}
if parent == nil {
n.parent = nil
return
}
n.parent = parent.(*binarySearchNodeMap)
}
func (n *binarySearchNodeMap) Left() rbtree.Node {
if n == nil {
return nil
}
return n.left
}
func (n *binarySearchNodeMap) SetLeft(left rbtree.Node) {
if n == nil {
addNewSearchNodeMapReceiver(&n)
}
if left == nil {
n.left = nil
return
}
n.left = left.(*binarySearchNodeMap)
}
func (n *binarySearchNodeMap) Right() rbtree.Node {
if n == nil {
return nil
}
return n.right
}
func (n *binarySearchNodeMap) SetRight(right rbtree.Node) {
if n == nil {
addNewSearchNodeMapReceiver(&n)
}
if right == nil {
n.right = nil
return
}
n.right = right.(*binarySearchNodeMap)
}
func (n *binarySearchNodeMap) IsRed() bool {
if n == nil {
return false
}
return n.colourIsRed
}
func (n *binarySearchNodeMap) SetRed(isRed bool) {
n.colourIsRed = isRed
}
func (n *binarySearchNodeMap) IsNil() bool {
return n == nil
}
func addNewSearchNodeMapReceiver(nodePtr **binarySearchNodeMap) {
*nodePtr = &binarySearchNodeMap{}
}
func (n *binarySearchNodeMap) insert(key []byte, pair MapPair) *binarySearchNodeMap {
if bytes.Equal(key, n.key) {
n.values = append(n.values, pair)
return nil // tree root does not change when replacing node
}
if bytes.Compare(key, n.key) < 0 {
if n.left != nil {
return n.left.insert(key, pair)
} else {
n.left = &binarySearchNodeMap{
key: key,
parent: n,
colourIsRed: true,
values: []MapPair{pair},
}
return binarySearchNodeMapFromRB(rbtree.Rebalance(n.left))
}
} else {
if n.right != nil {
return n.right.insert(key, pair)
} else {
n.right = &binarySearchNodeMap{
key: key,
parent: n,
colourIsRed: true,
values: []MapPair{pair},
}
return binarySearchNodeMapFromRB(rbtree.Rebalance(n.right))
}
}
}
func (n *binarySearchNodeMap) get(key []byte) ([]MapPair, error) {
if bytes.Equal(n.key, key) {
return sortAndDedupValues(n.values), nil
}
if bytes.Compare(key, n.key) < 0 {
if n.left == nil {
return nil, lsmkv.NotFound
}
return n.left.get(key)
} else {
if n.right == nil {
return nil, lsmkv.NotFound
}
return n.right.get(key)
}
}
func (n *binarySearchNodeMap) flattenInOrder() []*binarySearchNodeMap {
var left []*binarySearchNodeMap
var right []*binarySearchNodeMap
if n.left != nil {
left = n.left.flattenInOrder()
}
if n.right != nil {
right = n.right.flattenInOrder()
}
// the values are sorted on read for performance reasons, the assumption is
// that while a memtable is open writes a much more common, thus we write map
// KVs unsorted and only sort/dedup them on read.
right = append([]*binarySearchNodeMap{{
key: n.key,
values: sortAndDedupValues(n.values),
colourIsRed: n.colourIsRed,
}}, right...)
return append(left, right...)
}
// takes a list of MapPair and sorts it while keeping the original order. Then
// removes redundancies (from updates or deletes after previous inserts) using
// a simple deduplication process.
func sortAndDedupValues(in []MapPair) []MapPair {
out := make([]MapPair, len(in))
copy(out, in)
// use SliceStable so that we keep the insert order on duplicates. This is
// important because otherwise we can't dedup them correctly if we don't know
// in which order they came in.
sort.SliceStable(out, func(a, b int) bool {
return bytes.Compare(out[a].Key, out[b].Key) < 0
})
// now deduping is as simple as looking one key ahead - if it's the same key
// simply skip the current element. Meaning "out" will be a subset of
// (sorted) "in".
outIndex := 0
for inIndex, pair := range out {
// look ahead
if inIndex+1 < len(out) && bytes.Equal(out[inIndex+1].Key, pair.Key) {
continue
}
out[outIndex] = pair
outIndex++
}
return out[:outIndex]
}
func binarySearchNodeMapFromRB(rbNode rbtree.Node) (bsNode *binarySearchNodeMap) {
if rbNode == nil {
bsNode = nil
return
}
bsNode = rbNode.(*binarySearchNodeMap)
return
}