add diff redid doc

README.md

@@ -12,7 +12,7 @@ LedisDB now supports multiple databases as backend to store data, you can test a
 + Supports transaction using LMDB or BotlDB.
 + Supports lua scripting.
 + Supports expiration and ttl.
-+ Redis clients, like redis-cli, are supported directly.
++ Supports using redis-cli directly.
 + Multiple client API supports, including Go, Python, Lua(Openresty), C/C++, Node.js. 
 + Easy to embed in your own Go application. 
 + Restful API support, json/bson/msgpack output.

doc/DiffRedis.md

@@ -0,0 +1,60 @@
+
+LedisDB is not Redis, so you can not use some Redis clients for LedisDB directly. 
+But LedisDB uses Redis protocol for communication and many APIs are same as Redis, 
+so you can easily write your own LedisDB client based on a Redis one.
+
+Before you write a client, you must know some differences between LedisDB and Redis.
+
+## Data Structure
+
+LedisDB has no Strings data type but KV and Bitmap, any some Keys and Strings commands in Redis will only affect KV data, and "bit" commands affect Bitmap.
+
+## Del
+
+In Redis, `del` can delete all type data, like String, Hash, List, etc, but in LedisDB, `del` can only delete KV data. To delete other type data, you will use "clear" commands.
+
++ KV:     `del`, `mdel` 
++ Hash:   `hclear`, `mhclear` 
++ List:   `lclear`, `mlclear`
++ Set:    `sclear`, `msclear`  
++ Zset:   `zclear`, `mzclear`
++ Bitmap: `bclear`, `mbclear`
+
+## Expire, Persist, and TTL
+
+The same for Del.
+
++ KV:     `expire`, `persist`, `ttl` 
++ Hash:   `hexpire`, `hpersist`, `httl` 
++ List:   `lexpire`, `lpersist`, `lttl`
++ Set:    `sexpire`, `spersist`, `sttl`  
++ Zset:   `zexpire`, `zpersist`, `zttl`
++ Bitmap: `bexpire`, `bpersist`, `bttl`
+
+## ZSet
+
+ZSet only support int64 score, not double in Redis.
+
+## Transaction
+
+LedisDB supports ACID transaction using LMDB or BoltDB, maybe later it will support `multi`, `exec`, `discard`.
+
+Transaction API:
+
++ `begin`
++ `commit`
++ `rollback`
+
+## Scan
+
+LedisDB supplies `xscan`, etc, to fetch data iteratively.
+
++ KV:     `xscan`
++ Hash:   `hxscan`
++ List:   `lxscan`
++ Set:    `sxscan` 
++ Zset:   `zxscan`
++ Bitmap: `bxscan`
+
+
+Of course, LedisDB has not implemented all APIs in Redis, you can see full commands in commands.json, commands.doc or [wiki](https://github.com/siddontang/ledisdb/wiki/Commands).