TairHash

Introduction 中文说明

     TairHash is a hash data structure developed based on the redis module. TairHash not only has the same rich data interface and high performance as the native hash, but also can set the expiration and version for the field. TairHash provides an active expiration mechanism, even if the field is not accessed after expiration, it can be actively deleted to release the memory.

The main features：

• Field supports setting expire and version
• Support efficient active expire and passivity expire for field
• The cmd is similar to the native hash data type
• Support redis swapdb, rename, move and copy command

The principle of efficient expiration:

• Use a two-level sort index, the first level sorts the main key of tairhash, and the second level sorts the fields inside each tairhash
• The first-level uses the smallest ttl in the second-level for sorting, so the main key is globally ordered
• The built-in timer will periodically scan the first-level index to find out a key that has expired, and then check the secondary index of these keys to eliminate the expired fields. This is the active expire
• Every time a write operation to tairhash, the first level index will be checked first, and at most three fields will be expired, Note these fields may not belong to the key currently being operated, so in theory, the faster you write, the faster the elimination
• Every time you read or write a field, it will also trigger the expiration of the field itself
• All keys and fields in the sorting index are pointer references, no memory copy, no memory expansion problem

At the same time, we also open sourced an enhanced string structure, which can set the version number for value and support memcached semantics. For details, please refer to here

Quick Start

127.0.0.1:6379> EXHSET k f v ex 10
(integer) 1
127.0.0.1:6379> EXHGET k f
"v"
127.0.0.1:6379> EXISTS k
(integer) 1
127.0.0.1:6379> debug sleep 10
OK
(10.00s)
127.0.0.1:6379> EXISTS k
(integer) 0
127.0.0.1:6379> EXHGET k f
(nil)
127.0.0.1:6379> EXHSET k f v px 10000
(integer) 1
127.0.0.1:6379> EXHGET k f
"v"
127.0.0.1:6379> EXISTS k
(integer) 1
127.0.0.1:6379> debug sleep 10
OK
(10.00s)
127.0.0.1:6379> EXISTS k
(integer) 0
127.0.0.1:6379> EXHGET k f
(nil)
127.0.0.1:6379> EXHSET k f v  VER 1
(integer) 1
127.0.0.1:6379> EXHSET k f v  VER 1
(integer) 0
127.0.0.1:6379> EXHSET k f v  VER 1
(error) ERR update version is stale
127.0.0.1:6379> EXHSET k f v  ABS 1
(integer) 0
127.0.0.1:6379> EXHSET k f v  ABS 2
(integer) 0
127.0.0.1:6379> EXHVER k f
(integer) 2

BUILD

mkdir build  
cd build  
cmake ../ && make -j

then the tairhash_module.so library file will be generated in the lib directory

TEST

1. Modify the path in the tairhash.tcl file in the tests directory to set testmodule [file your_path/tairhash_module.so]
2. Add the path of the tairhash.tcl file in the tests directory to the all_tests of redis test_helper.tcl
3. run ./runtest --single tairhash

Client

Java : https://github.com/aliyun/alibabacloud-tairjedis-sdk

API

Reference

Applicable Redis version

Since TairHash relies on the unlink2 callback function to release the index structure synchronously, you need to make sure that REDISMODULE_TYPE_METHOD_VERSION in your Redis is not less than 4.