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package main
import (
"hash/fnv"
"sort"
"sync"
)
type Shard struct{
mu sync.Mutex
id int
data map[string]Item
}
func (db *RedisDB) getShard(key string)*Shard{
hash := fnv.New64a()
hash.Write([]byte(key))
val := hash.Sum64()
return db.shards[val%NumShards]
}
func (db *RedisDB) Execute(key string, fn func(*Shard) interface{}) interface{} {
shard := db.getShard(key)
shard.mu.Lock()
defer shard.mu.Unlock()
return fn(shard)
}
func ( db *RedisDB) ExecuteMulti(keys []string, fn func([]*Shard) interface{})interface{}{
shardMap := make(map[int]*Shard)
for _, k := range keys {
shard := db.getShard(k)
shardMap[shard.id] = shard
}
var sortedIDs []int
for id := range shardMap {
sortedIDs = append(sortedIDs, id)
}
sort.Ints(sortedIDs)
for _, id := range sortedIDs{
shardMap[id].mu.Lock()
}
defer func(){
for i := len(sortedIDs)-1; i >= 0; i --{
shardMap[sortedIDs[i]].mu.Unlock()
}
}()
shards := make([]*Shard, 0, len(shardMap))
for _, id := range sortedIDs {
shards = append(shards, shardMap[id])
}
return fn(shards)
}
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