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ItemList.go
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ItemList.go
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package redis3
import (
"bytes"
"context"
"fmt"
"github.com/go-redis/redis/v8"
"github.com/seaweedfs/seaweedfs/weed/util/skiplist"
)
type ItemList struct {
skipList *skiplist.SkipList
batchSize int
client redis.UniversalClient
prefix string
}
func newItemList(client redis.UniversalClient, prefix string, store skiplist.ListStore, batchSize int) *ItemList {
return &ItemList{
skipList: skiplist.New(store),
batchSize: batchSize,
client: client,
prefix: prefix,
}
}
/*
Be reluctant to create new nodes. Try to fit into either previous node or next node.
Prefer to add to previous node.
There are multiple cases after finding the name for greater or equal node
1. found and node.Key == name
The node contains a batch with leading key the same as the name
nothing to do
2. no such node found or node.Key > name
if no such node found
prevNode = list.LargestNode
// case 2.1
if previousNode contains name
nothing to do
// prefer to add to previous node
if prevNode != nil {
// case 2.2
if prevNode has capacity
prevNode.add name, and save
return
// case 2.3
split prevNode by name
}
// case 2.4
// merge into next node. Avoid too many nodes if adding data in reverse order.
if nextNode is not nil and nextNode has capacity
delete nextNode.Key
nextNode.Key = name
nextNode.batch.add name
insert nodeNode.Key
return
// case 2.5
if prevNode is nil
insert new node with key = name, value = batch{name}
return
*/
func (nl *ItemList) canAddMember(node *skiplist.SkipListElementReference, name string) (alreadyContains bool, nodeSize int, err error) {
ctx := context.Background()
pipe := nl.client.TxPipeline()
key := fmt.Sprintf("%s%dm", nl.prefix, node.ElementPointer)
countOperation := pipe.ZLexCount(ctx, key, "-", "+")
scoreOperationt := pipe.ZScore(ctx, key, name)
if _, err = pipe.Exec(ctx); err != nil && err != redis.Nil {
return false, 0, err
}
if err == redis.Nil {
err = nil
}
alreadyContains = scoreOperationt.Err() == nil
nodeSize = int(countOperation.Val())
return
}
func (nl *ItemList) WriteName(name string) error {
lookupKey := []byte(name)
prevNode, nextNode, found, err := nl.skipList.FindGreaterOrEqual(lookupKey)
if err != nil {
return err
}
// case 1: the name already exists as one leading key in the batch
if found && bytes.Compare(nextNode.Key, lookupKey) == 0 {
return nil
}
var prevNodeReference *skiplist.SkipListElementReference
if !found {
prevNodeReference = nl.skipList.GetLargestNodeReference()
}
if nextNode != nil && prevNode == nil {
prevNodeReference = nextNode.Prev
}
if prevNodeReference != nil {
alreadyContains, nodeSize, err := nl.canAddMember(prevNodeReference, name)
if err != nil {
return err
}
if alreadyContains {
// case 2.1
return nil
}
// case 2.2
if nodeSize < nl.batchSize {
return nl.NodeAddMember(prevNodeReference, name)
}
// case 2.3
x := nl.NodeInnerPosition(prevNodeReference, name)
y := nodeSize - x
addToX := x <= y
// add to a new node
if x == 0 || y == 0 {
if err := nl.ItemAdd(lookupKey, 0, name); err != nil {
return err
}
return nil
}
if addToX {
// collect names before name, add them to X
namesToX, err := nl.NodeRangeBeforeExclusive(prevNodeReference, name)
if err != nil {
return nil
}
// delete skiplist reference to old node
if _, err := nl.skipList.DeleteByKey(prevNodeReference.Key); err != nil {
return err
}
// add namesToY and name to a new X
namesToX = append(namesToX, name)
if err := nl.ItemAdd([]byte(namesToX[0]), 0, namesToX...); err != nil {
return nil
}
// remove names less than name from current Y
if err := nl.NodeDeleteBeforeExclusive(prevNodeReference, name); err != nil {
return nil
}
// point skip list to current Y
if err := nl.ItemAdd(lookupKey, prevNodeReference.ElementPointer); err != nil {
return nil
}
return nil
} else {
// collect names after name, add them to Y
namesToY, err := nl.NodeRangeAfterExclusive(prevNodeReference, name)
if err != nil {
return nil
}
// add namesToY and name to a new Y
namesToY = append(namesToY, name)
if err := nl.ItemAdd(lookupKey, 0, namesToY...); err != nil {
return nil
}
// remove names after name from current X
if err := nl.NodeDeleteAfterExclusive(prevNodeReference, name); err != nil {
return nil
}
return nil
}
}
// case 2.4
if nextNode != nil {
nodeSize := nl.NodeSize(nextNode.Reference())
if nodeSize < nl.batchSize {
if id, err := nl.skipList.DeleteByKey(nextNode.Key); err != nil {
return err
} else {
if err := nl.ItemAdd(lookupKey, id, name); err != nil {
return err
}
}
return nil
}
}
// case 2.5
// now prevNode is nil
return nl.ItemAdd(lookupKey, 0, name)
}
/*
// case 1: exists in nextNode
if nextNode != nil && nextNode.Key == name {
remove from nextNode, update nextNode
// TODO: merge with prevNode if possible?
return
}
if nextNode is nil
prevNode = list.Largestnode
if prevNode == nil and nextNode.Prev != nil
prevNode = load(nextNode.Prev)
// case 2: does not exist
// case 2.1
if prevNode == nil {
return
}
// case 2.2
if prevNameBatch does not contain name {
return
}
// case 3
delete from prevNameBatch
if prevNameBatch + nextNode < capacityList
// case 3.1
merge
else
// case 3.2
update prevNode
*/
func (nl *ItemList) DeleteName(name string) error {
lookupKey := []byte(name)
prevNode, nextNode, found, err := nl.skipList.FindGreaterOrEqual(lookupKey)
if err != nil {
return err
}
// case 1
if found && bytes.Compare(nextNode.Key, lookupKey) == 0 {
if _, err := nl.skipList.DeleteByKey(nextNode.Key); err != nil {
return err
}
if err := nl.NodeDeleteMember(nextNode.Reference(), name); err != nil {
return err
}
minName := nl.NodeMin(nextNode.Reference())
if minName == "" {
return nl.NodeDelete(nextNode.Reference())
}
return nl.ItemAdd([]byte(minName), nextNode.Id)
}
if !found {
prevNode, err = nl.skipList.GetLargestNode()
if err != nil {
return err
}
}
if nextNode != nil && prevNode == nil {
prevNode, err = nl.skipList.LoadElement(nextNode.Prev)
if err != nil {
return err
}
}
// case 2
if prevNode == nil {
// case 2.1
return nil
}
if !nl.NodeContainsItem(prevNode.Reference(), name) {
return nil
}
// case 3
if err := nl.NodeDeleteMember(prevNode.Reference(), name); err != nil {
return err
}
prevSize := nl.NodeSize(prevNode.Reference())
if prevSize == 0 {
if _, err := nl.skipList.DeleteByKey(prevNode.Key); err != nil {
return err
}
return nil
}
nextSize := nl.NodeSize(nextNode.Reference())
if nextSize > 0 && prevSize+nextSize < nl.batchSize {
// case 3.1 merge nextNode and prevNode
if _, err := nl.skipList.DeleteByKey(nextNode.Key); err != nil {
return err
}
nextNames, err := nl.NodeRangeBeforeExclusive(nextNode.Reference(), "")
if err != nil {
return err
}
if err := nl.NodeAddMember(prevNode.Reference(), nextNames...); err != nil {
return err
}
return nl.NodeDelete(nextNode.Reference())
} else {
// case 3.2 update prevNode
// no action to take
return nil
}
return nil
}
func (nl *ItemList) ListNames(startFrom string, visitNamesFn func(name string) bool) error {
lookupKey := []byte(startFrom)
prevNode, nextNode, found, err := nl.skipList.FindGreaterOrEqual(lookupKey)
if err != nil {
return err
}
if found && bytes.Compare(nextNode.Key, lookupKey) == 0 {
prevNode = nil
}
if !found {
prevNode, err = nl.skipList.GetLargestNode()
if err != nil {
return err
}
}
if prevNode != nil {
if !nl.NodeScanInclusiveAfter(prevNode.Reference(), startFrom, visitNamesFn) {
return nil
}
}
for nextNode != nil {
if !nl.NodeScanInclusiveAfter(nextNode.Reference(), startFrom, visitNamesFn) {
return nil
}
nextNode, err = nl.skipList.LoadElement(nextNode.Next[0])
if err != nil {
return err
}
}
return nil
}
func (nl *ItemList) RemoteAllListElement() error {
t := nl.skipList
nodeRef := t.StartLevels[0]
for nodeRef != nil {
node, err := t.LoadElement(nodeRef)
if err != nil {
return err
}
if node == nil {
return nil
}
if err := t.DeleteElement(node); err != nil {
return err
}
if err := nl.NodeDelete(node.Reference()); err != nil {
return err
}
nodeRef = node.Next[0]
}
return nil
}
func (nl *ItemList) NodeContainsItem(node *skiplist.SkipListElementReference, item string) bool {
key := fmt.Sprintf("%s%dm", nl.prefix, node.ElementPointer)
_, err := nl.client.ZScore(context.Background(), key, item).Result()
if err == redis.Nil {
return false
}
if err == nil {
return true
}
return false
}
func (nl *ItemList) NodeSize(node *skiplist.SkipListElementReference) int {
if node == nil {
return 0
}
key := fmt.Sprintf("%s%dm", nl.prefix, node.ElementPointer)
return int(nl.client.ZLexCount(context.Background(), key, "-", "+").Val())
}
func (nl *ItemList) NodeAddMember(node *skiplist.SkipListElementReference, names ...string) error {
key := fmt.Sprintf("%s%dm", nl.prefix, node.ElementPointer)
var members []*redis.Z
for _, name := range names {
members = append(members, &redis.Z{
Score: 0,
Member: name,
})
}
return nl.client.ZAddNX(context.Background(), key, members...).Err()
}
func (nl *ItemList) NodeDeleteMember(node *skiplist.SkipListElementReference, name string) error {
key := fmt.Sprintf("%s%dm", nl.prefix, node.ElementPointer)
return nl.client.ZRem(context.Background(), key, name).Err()
}
func (nl *ItemList) NodeDelete(node *skiplist.SkipListElementReference) error {
key := fmt.Sprintf("%s%dm", nl.prefix, node.ElementPointer)
return nl.client.Del(context.Background(), key).Err()
}
func (nl *ItemList) NodeInnerPosition(node *skiplist.SkipListElementReference, name string) int {
key := fmt.Sprintf("%s%dm", nl.prefix, node.ElementPointer)
return int(nl.client.ZLexCount(context.Background(), key, "-", "("+name).Val())
}
func (nl *ItemList) NodeMin(node *skiplist.SkipListElementReference) string {
key := fmt.Sprintf("%s%dm", nl.prefix, node.ElementPointer)
slice := nl.client.ZRangeByLex(context.Background(), key, &redis.ZRangeBy{
Min: "-",
Max: "+",
Offset: 0,
Count: 1,
}).Val()
if len(slice) > 0 {
s := slice[0]
return s
}
return ""
}
func (nl *ItemList) NodeScanInclusiveAfter(node *skiplist.SkipListElementReference, startFrom string, visitNamesFn func(name string) bool) bool {
key := fmt.Sprintf("%s%dm", nl.prefix, node.ElementPointer)
if startFrom == "" {
startFrom = "-"
} else {
startFrom = "[" + startFrom
}
names := nl.client.ZRangeByLex(context.Background(), key, &redis.ZRangeBy{
Min: startFrom,
Max: "+",
}).Val()
for _, n := range names {
if !visitNamesFn(n) {
return false
}
}
return true
}
func (nl *ItemList) NodeRangeBeforeExclusive(node *skiplist.SkipListElementReference, stopAt string) ([]string, error) {
key := fmt.Sprintf("%s%dm", nl.prefix, node.ElementPointer)
if stopAt == "" {
stopAt = "+"
} else {
stopAt = "(" + stopAt
}
return nl.client.ZRangeByLex(context.Background(), key, &redis.ZRangeBy{
Min: "-",
Max: stopAt,
}).Result()
}
func (nl *ItemList) NodeRangeAfterExclusive(node *skiplist.SkipListElementReference, startFrom string) ([]string, error) {
key := fmt.Sprintf("%s%dm", nl.prefix, node.ElementPointer)
if startFrom == "" {
startFrom = "-"
} else {
startFrom = "(" + startFrom
}
return nl.client.ZRangeByLex(context.Background(), key, &redis.ZRangeBy{
Min: startFrom,
Max: "+",
}).Result()
}
func (nl *ItemList) NodeDeleteBeforeExclusive(node *skiplist.SkipListElementReference, stopAt string) error {
key := fmt.Sprintf("%s%dm", nl.prefix, node.ElementPointer)
if stopAt == "" {
stopAt = "+"
} else {
stopAt = "(" + stopAt
}
return nl.client.ZRemRangeByLex(context.Background(), key, "-", stopAt).Err()
}
func (nl *ItemList) NodeDeleteAfterExclusive(node *skiplist.SkipListElementReference, startFrom string) error {
key := fmt.Sprintf("%s%dm", nl.prefix, node.ElementPointer)
if startFrom == "" {
startFrom = "-"
} else {
startFrom = "(" + startFrom
}
return nl.client.ZRemRangeByLex(context.Background(), key, startFrom, "+").Err()
}
func (nl *ItemList) ItemAdd(lookupKey []byte, idIfKnown int64, names ...string) error {
if id, err := nl.skipList.InsertByKey(lookupKey, idIfKnown, nil); err != nil {
return err
} else {
if len(names) > 0 {
return nl.NodeAddMember(&skiplist.SkipListElementReference{
ElementPointer: id,
Key: lookupKey,
}, names...)
}
}
return nil
}