Redka - 父亲是Redis，母亲是SQLite
Redka 旨在使用 SQLite 重新实现 Redis 的优秀部分,同时保持与 Redis API 的兼容性。
有意思的特性:
- 数据不必完全装载在内存中。
- 支持 ACID 事务。
- 使用 SQL 视图以便于内省和报告。
- 同时提供进程内(Go API)和独立(RESP)服务器。
- 兼容 Redis 的命令和线路协议。
Redia 并不期望完全达到 Redis 那么高的性能，但是性能上也并不会落后很多。它的主要功能还是 SQL + Redis 的功能，集成了两种优秀产品 SQLite 和 Redis 的盛世美颜。
支持的 Redis 命令
字符串
Command Go API Description
------- ------ -----------
DECR DB.Str().Incr Decrements the integer value of a key by one.
DECRBY DB.Str().Incr Decrements a number from the integer value of a key.
GET DB.Str().Get Returns the value of a key.
GETSET DB.Str().SetWith Sets the key to a new value and returns the prev value.
INCR DB.Str().Incr Increments the integer value of a key by one.
INCRBY DB.Str().Incr Increments the integer value of a key by a number.
INCRBYFLOAT DB.Str().IncrFloat Increments the float value of a key by a number.
MGET DB.Str().GetMany Returns the values of one or more keys.
MSET DB.Str().SetMany Sets the values of one or more keys.
PSETEX DB.Str().SetExpires Sets the value and expiration time (in ms) of a key.
SET DB.Str().Set Sets the value of a key.
SETEX DB.Str().SetExpires Sets the value and expiration (in sec) time of a key.
SETNX DB.Str().SetWith Sets the value of a key when the key doesn't exist.暂时不支持的命令
APPEND GETDEL GETEX GETRANGE LCS MSETNX SETRANGE STRLEN SUBSTR列表
Command Go API Description
------- ------ -----------
LINDEX DB.List().Get Returns an element by its index.
LINSERT DB.List().Insert* Inserts an element before or after another element.
LLEN DB.List().Len Returns the length of a list.
LPOP DB.List().PopFront Returns the first element after removing it.
LPUSH DB.List().PushFront Prepends an element to a list.
LRANGE DB.List().Range Returns a range of elements.
LREM DB.List().Delete* Removes elements from a list.
LSET DB.List().Set Sets the value of an element by its index.
LTRIM DB.List().Trim Removes elements from both ends a list.
RPOP DB.List().PopBack Returns the last element after removing it.
RPOPLPUSH DB.List().PopBackPushFront Removes the last element and pushes it to another list.
RPUSH DB.List().PushBack Appends an element to a list.暂时不支持的命令
BLMOVE BLMPOP BLPOP BRPOP BRPOPLPUSH LMOVE LMPOP
LPOS LPUSHX RPUSHXSet
Command Go API Description
------- ------ -----------
SADD DB.Set().Add Adds one or more members to a set.
SCARD DB.Set().Len Returns the number of members in a set.
SDIFF DB.Set().Diff Returns the difference of multiple sets.
SDIFFSTORE DB.Set().DiffStore Stores the difference of multiple sets.
SINTER DB.Set().Inter Returns the intersection of multiple sets.
SINTERSTORE DB.Set().InterStore Stores the intersection of multiple sets.
SISMEMBER DB.Set().Exists Determines whether a member belongs to a set.
SMEMBERS DB.Set().Items Returns all members of a set.
SMOVE DB.Set().Move Moves a member from one set to another.
SPOP DB.Set().Pop Returns a random member after removing it.
SRANDMEMBER DB.Set().Random Returns a random member from a set.
SREM DB.Set().Delete Removes one or more members from a set.
SSCAN DB.Set().Scanner Iterates over members of a set.
SUNION DB.Set().Union Returns the union of multiple sets.
SUNIONSTORE DB.Set().UnionStore Stores the union of multiple sets.暂时不支持的命令
SINTERCARD SMISMEMBERHash
Command Go API Description
------- ------------------ -----------
HDEL DB.Hash().Delete Deletes one or more fields and their values.
HEXISTS DB.Hash().Exists Determines whether a field exists.
HGET DB.Hash().Get Returns the value of a field.
HGETALL DB.Hash().Items Returns all fields and values.
HINCRBY DB.Hash().Incr Increments the integer value of a field.
HINCRBYFLOAT DB.Hash().IncrFloat Increments the float value of a field.
HKEYS DB.Hash().Keys Returns all fields.
HLEN DB.Hash().Len Returns the number of fields.
HMGET DB.Hash().GetMany Returns the values of multiple fields.
HMSET DB.Hash().SetMany Sets the values of multiple fields.
HSCAN DB.Hash().Scanner Iterates over fields and values.
HSET DB.Hash().SetMany Sets the values of one or more fields.
HSETNX DB.Hash().SetNotExists Sets the value of a field when it doesn't exist.
HVALS DB.Hash().Exists Returns all values.暂时不支持的命令
HRANDFIELD HSTRLENSorted Set
Command Go API Description
------- ------ -----------
ZADD DB.ZSet().AddMany Adds or updates one or more members of a set.
ZCARD DB.ZSet().Len Returns the number of members in a set.
ZCOUNT DB.ZSet().Count Returns the number of members of a set within a range of scores.
ZINCRBY DB.ZSet().Incr Increments the score of a member in a set.
ZINTER DB.ZSet().InterWith Returns the intersection of multiple sets.
ZINTERSTORE DB.ZSet().InterWith Stores the intersection of multiple sets in a key.
ZRANGE DB.ZSet().RangeWith Returns members of a set within a range of indexes.
ZRANGEBYSCORE DB.ZSet().RangeWith Returns members of a set within a range of scores.
ZRANK DB.ZSet().GetRank Returns the index of a member in a set ordered by ascending scores.
ZREM DB.ZSet().Delete Removes one or more members from a set.
ZREMRANGEBYRANK DB.ZSet().DeleteWith Removes members of a set within a range of indexes.
ZREMRANGEBYSCORE DB.ZSet().DeleteWith Removes members of a set within a range of scores.
ZREVRANGE DB.ZSet().RangeWith Returns members of a set within a range of indexes in reverse order.
ZREVRANGEBYSCORE DB.ZSet().RangeWith Returns members of a set within a range of scores in reverse order.
ZREVRANK DB.ZSet().GetRankRev Returns the index of a member in a set ordered by descending scores.
ZSCAN DB.ZSet().Scan Iterates over members and scores of a set.
ZSCORE DB.ZSet().GetScore Returns the score of a member in a set.
ZUNION DB.ZSet().UnionWith Returns the union of multiple sets.
ZUNIONSTORE DB.ZSet().UnionWith Stores the union of multiple sets in a key.不支持的命令
BZMPOP BZPOPMAX BZPOPMIN ZDIFF ZDIFFSTORE ZINTERCARD
ZLEXCOUNT ZMPOP ZMSCORE ZPOPMAX ZPOPMIN ZRANDMEMBER
ZRANGEBYLEX ZRANGESTORE ZREMRANGEBYLEX ZREVRANGEBYLEXKey
Command Go API Description
------- ------ -----------
DBSIZE DB.Key().Len Returns the total number of keys.
DEL DB.Key().Delete Deletes one or more keys.
EXISTS DB.Key().Count Determines whether one or more keys exist.
EXPIRE DB.Key().Expire Sets the expiration time of a key (in seconds).
EXPIREAT DB.Key().ExpireAt Sets the expiration time of a key to a Unix timestamp.
FLUSHDB DB.Key().DeleteAll Deletes all keys from the database.
KEYS DB.Key().Keys Returns all key names that match a pattern.
PERSIST DB.Key().Persist Removes the expiration time of a key.
PEXPIRE DB.Key().Expire Sets the expiration time of a key in ms.
PEXPIREAT DB.Key().ExpireAt Sets the expiration time of a key to a Unix ms timestamp.
RANDOMKEY DB.Key().Random Returns a random key name from the database.
RENAME DB.Key().Rename Renames a key and overwrites the destination.
RENAMENX DB.Key().RenameNotExists Renames a key only when the target key name doesn't exist.
SCAN DB.Key().Scanner Iterates over the key names in the database.
TTL DB.Key().Get Returns the expiration time in seconds of a key.
TYPE DB.Key().Get Returns the type of value stored at a key.不支持的命令
COPY DUMP EXPIRETIME MIGRATE MOVE OBJECT PEXPIRETIME
PTTL RESTORE SORT SORT_RO TOUCH TTL TYPE UNLINK
WAIT WAITAOF事务
Command Go API Description
------- ------ -----------
DISCARD DB.View / DB.Update Discards a transaction.
EXEC DB.View / DB.Update Executes all commands in a transaction.
MULTI DB.View / DB.Update Starts a transaction.与 Redis 不同，Redka 的事务完全符合 ACID 属性，在发生故障时会自动回滚。
不支持的命令
UNWATCH WATCH连接管理
Command Go API Description
------- ------ -----------
ECHO - Returns the given string.
PING - Returns the server's liveliness response.安装
你可以以独立的服务的形式安装。官方文档提供了方便的 Linux、macOS 的安装脚本，你也可以使用 docker 进行部署。
也可以在你的 Go 程序中当成一个库引用: go get github.com/nalgeon/redka，当然了你也必须引入 sqlite 的库，比如 github.com/mattn/go-sqlite3 或者 modernc.org/sqlite。
运行
你可以使用 redka [-h host] [-p port] [db-path] 启动一个 redka 服务，比如
./redka
./redka data.db
./redka -h 0.0.0.0 -p 6379 data.db如果没有指定数据库文件，那么它就完全使用内存的方式。
如果当成一个库引入使用，你可以像这样在进程内使用:\
package main
import (
"log"
_ "github.com/mattn/go-sqlite3"
"github.com/nalgeon/redka"
)
func main() {
// Open or create the data.db file.
db, err := redka.Open("data.db", nil)
if err != nil {
log.Fatal(err)
}
// Always close the database when you are finished.
defer db.Close()
// ...
}如果是使用内存的方式，可以指定 sqlite 使用内存的方式打开:
// All data is lost when the database is closed.
redka.Open("file:redka?mode=memory&cache=shared")然后代码中就可以直接调用：
db.Str().Set("name", "alice")
db.Str().Set("age", 25)
count, err := db.Key().Count("name", "age", "city")
slog.Info("count", "count", count, "err", err)
name, err := db.Str().Get("name")
slog.Info("get", "name", name, "err", err)下面的代码是使用事务的例子：
updCount := 0
err := db.Update(func(tx *redka.Tx) error {
err := tx.Str().Set("name", "bob")
if err != nil {
return err
}
updCount++
err = tx.Str().Set("age", 50)
if err != nil {
return err
}
updCount++
return nil
})
slog.Info("updated", "count", updCount, "err", err)性能
作者在 Apple M1 8-core CPU, 16GB RAM 的苹果机器和 Redis 进行了性能比较。 使用下面的场景进行比较(redis-benchmark -p 6379 -q -c 10 -n 1000000 -r 10000 -t get,set)：
- 10 parallel connections
- 1000000 requests
- 10000 randomized keys
- GET/SET commands
比 Redis 慢 2~5 倍，这也合理，毕竟底层采用一个关系数据库进行存储。
给我们的启发
Redka 使用 redcon 进行 Redis 命令的解析，然后针对每种大类的 Redis 命令，会有一个单独的表进行存储。
rkey
---
id integer primary key
key text not null
type integer not null -- 1 string, 2 list, 3 set, 4 hash, 5 sorted set
version integer not null -- incremented when the key value is updated
etime integer -- expiration timestamp in unix milliseconds
mtime integer not null -- modification timestamp in unix milliseconds
len integer -- number of child elements
rstring
---
kid integer not null -- FK -> rkey.id
value blob not null
rlist
---
kid integer not null -- FK -> rkey.id
pos real not null -- is used for ordering, but is not an index
elem blob not null
rset
---
kid integer not null -- FK -> rkey.id
elem blob not null
rhash
---
kid integer not null -- FK -> rkey.id
field text not null
value blob not null
rzset
---
kid integer not null -- FK -> rkey.id
elem blob not null
score real not null既然它支持 sqlite, 我们可以把它 port 到其它的数据库上，比如 clickhouse，这样我们就可以支持巨量的数据了。
当然更深一步，我们还可以接入其他的 NoSQL 数据库，比如 RocksDB 等，类似的项目都有很多了。
这是一个很有意思的项目。