DRDS 全局二级索引 (Global Secondary Index, GSI)

#DRDS 全局二级索引 (Global Secondary Index, GSI)


###一、版本限制

MySQL 版本 >= 5.7, 并且 DRDS 版本 >= 5.4.1

###二、 基本原理

1、主表+索引表(每个GSI对应一张索引表)-》下发到每一个分库中
2、写=》如何保证分库一致的?通过XA事务
3、读=》先读索引表,查询列中索引表的覆盖列全部包括,直接返回索引表数据,否则回表处理(回查主表取得缺失列的值)
###三、 使用

1、创建
DRDS 对 MySQL DDL 语法进行了扩展,增加定义 GSI 的语法。使用方式与在 MySQL 上创建索引一致:
建表时定义 GSI

在这里插入图片描述

建表后添加 GSI
在这里插入图片描述

其中:
索引名 :作为索引表的名字,用于创建索引表
索引列 :索引表的分库分表键,即索引分库分表子句中用到的所有列
覆盖列 :索引表中的其他列,默认包含主键和主表的全部分库分表键
索引分库分表子句 :索引表的分库分表算法,与 CREATE TABLE 中分库分表子句的语法一致

2、 使用
1)通过 HINT 指定索引
FORCE INDEX({index_name})
/+TDDL:INDEX({table_name/table_alias}, {index_name})/
IGNORE INDEX与USE INDEX 不使用那些索引、使用那些索引
2)索引选择
对于带有全局二级索引的主表查询,DRDS会自动选择出优化器认为代价最低的索引表。(目前只支持覆盖索引选择)

!!#ff0000 *特别要注意在使用的时候有一些限制和约定(DML、DDL)!!

###四、 FAQ

1、 全局二级索引解决什么问题?

如果查询的维度与逻辑表的拆分维度不同,会产生跨分片查询。随着跨分片查询增多,会产生查询卡慢、连接池耗尽等性能问题。GSI 通过增加拆分维度来减少跨分片查询,消除性能瓶颈,创建 GSI 时需要注意选择与主表不同的分库分表键。

2、 全局二级索引和局部索引的关系?

局部索引: 分布式数据库中,如果数据行和对应的索引行保存在相同分片上,称这种索引为局部索引。DRDS 中特指物理表上的 MySQL 二级索引
全局二级索引: 不同于局部索引,如果数据行和对应的索引行保存在不同分片上,称这种索引为全局二级索引,主要用于快速确定查询涉及的数据分片
两者的关系: 需要搭配使用,DRDS 通过 GSI 将查询下发到单个分片后,该分片上的局部索引能够提升分片内的查询性能。

###五、 性能对比

执行环境

  • CPU:2.6 GHz 六核Intel Core i7
  • 内存:16G
  • 操作系统:macOS Catalina(10.15.2)
  • 同一个docker容器中

####压测工具

ab -c 100 -n 10000 -k url


####执行流程

api->userRpc->db


####测试流程

SELECT COUNT() FROM users; !!#ff0000 COUNT():10w+!!

1、 读取一行数据(select *)

1)drds(5.6.29-TDDL-5.3.7-15460044)主表执行
执行的sql:
!!#0000ff SELECT * FROM users WHERE mobile=’;!!

joex@joexdembp ~ % ab -c 100 -n 10000 http://127.0.0.1/
This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 127.0.0.1 (be patient)
Completed 1000 requests
Completed 2000 requests
Completed 3000 requests
Completed 4000 requests
Completed 5000 requests
Completed 6000 requests
Completed 7000 requests
Completed 8000 requests
Completed 9000 requests
Completed 10000 requests
Finished 10000 requests


Server Software:        swoole-http-server
Server Hostname:        127.0.0.1
Server Port:            80

Document Path:          /
Document Length:        353 bytes

Concurrency Level:      100
Time taken for tests:   12.148 seconds
Complete requests:      10000
Failed requests:        0
Total transferred:      7130000 bytes
HTML transferred:       3530000 bytes
Requests per second:    823.16 [#/sec] (mean)
Time per request:       121.483 [ms] (mean)
Time per request:       1.215 [ms] (mean, across all concurrent requests)
Transfer rate:          573.16 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.3      0       5
Processing:    42  119  42.8    111     766
Waiting:       41  119  42.8    111     766
Total:         42  120  42.8    112     766

Percentage of the requests served within a certain time (ms)
  50%    112
  66%    123
  75%    133
  80%    139
  90%    160
  95%    184
  98%    242
  99%    321
 100%    766 (longest request)

2)drds(5.6.29-TDDL-5.3.7-15460044)冗余表索引+主表缺失列回查执行
执行的sql:
!!#0000ff SELECT * FROM redundance_mobile WHERE mobile=’’;!!

!!#0000ff SELECT * FROM users WHERE uid=;!!

joex@joexdembp ~ % ab -c 100 -n 10000 http://127.0.0.1/
This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 127.0.0.1 (be patient)
Completed 1000 requests
Completed 2000 requests
Completed 3000 requests
Completed 4000 requests
Completed 5000 requests
Completed 6000 requests
Completed 7000 requests
Completed 8000 requests
Completed 9000 requests
Completed 10000 requests
Finished 10000 requests


Server Software:        swoole-http-server
Server Hostname:        127.0.0.1
Server Port:            80

Document Path:          /
Document Length:        353 bytes

Concurrency Level:      100
Time taken for tests:   19.521 seconds
Complete requests:      10000
Failed requests:        0
Total transferred:      7130000 bytes
HTML transferred:       3530000 bytes
Requests per second:    512.28 [#/sec] (mean)
Time per request:       195.207 [ms] (mean)
Time per request:       1.952 [ms] (mean, across all concurrent requests)
Transfer rate:          356.69 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.3      0       7
Processing:    57  192 101.8    155     824
Waiting:       56  192 101.7    155     824
Total:         60  192 101.8    155     824

Percentage of the requests served within a certain time (ms)
  50%    155
  66%    171
  75%    185
  80%    199
  90%    391
  95%    440
  98%    478
  99%    514
 100%    824 (longest request)

3)drds(5.6.29-TDDL-5.4.4-15864860)全局二级索引执行
执行的sql:
!!#0000ff SELECT * FROM users WHERE mobile=’’;!!

joex@joexdembp ~ % ab -c 100 -n 10000 http://127.0.0.1/
This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 127.0.0.1 (be patient)
Completed 1000 requests
Completed 2000 requests
Completed 3000 requests
Completed 4000 requests
Completed 5000 requests
Completed 6000 requests
Completed 7000 requests
Completed 8000 requests
Completed 9000 requests
Completed 10000 requests
Finished 10000 requests


Server Software:        swoole-http-server
Server Hostname:        127.0.0.1
Server Port:            80

Document Path:          /
Document Length:        353 bytes

Concurrency Level:      100
Time taken for tests:   14.018 seconds
Complete requests:      10000
Failed requests:        0
Total transferred:      7130000 bytes
HTML transferred:       3530000 bytes
Requests per second:    713.37 [#/sec] (mean)
Time per request:       140.181 [ms] (mean)
Time per request:       1.402 [ms] (mean, across all concurrent requests)
Transfer rate:          496.71 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   1.8      0     181
Processing:    27  139  49.4    127     451
Waiting:       22  139  49.3    127     451
Total:         28  139  49.4    127     451

Percentage of the requests served within a certain time (ms)
  50%    127
  66%    141
  75%    152
  80%    161
  90%    210
  95%    257
  98%    287
  99%    302
 100%    451 (longest request)

|ab并发和请求数|数据库环境|执行时间(5次平均值)|QPS(每秒请求数)(5次平均值)|
|100并发,10000请求|drds(5.6.29-TDDL-5.3.7-15460044)主表执行|14.62 seconds|713|
||100并发,10000请求||drds(5.6.29-TDDL-5.3.7-15460044)冗余表索引+主表缺失列回查执行|| 19.77 seconds||514||
||100并发,10000请求||drds(5.6.29-TDDL-5.4.4-15864860)全局二级索引|| 17.18 seconds||592||

DRDS 全局二级索引 (Global Secondary Index, GSI)_第1张图片


2、 读取一行数据(select uid mobile)查询二级索引/索引表(不回表)
1)drds(5.6.29-TDDL-5.3.7-15460044)冗余表
执行的sql:
!!#0000ff SELECT uid,mobile FROM redundance_mobile WHERE mobile=’’;!!

joex@joexdembp ~ % ab -c 100 -n 10000 http://127.0.0.1/
This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 127.0.0.1 (be patient)
Completed 1000 requests
Completed 2000 requests
Completed 3000 requests
Completed 4000 requests
Completed 5000 requests
Completed 6000 requests
Completed 7000 requests
Completed 8000 requests
Completed 9000 requests
Completed 10000 requests
Finished 10000 requests


Server Software:        swoole-http-server
Server Hostname:        127.0.0.1
Server Port:            80

Document Path:          /
Document Length:        353 bytes

Concurrency Level:      100
Time taken for tests:   15.822 seconds
Complete requests:      10000
Failed requests:        0
Total transferred:      7130000 bytes
HTML transferred:       3530000 bytes
Requests per second:    632.03 [#/sec] (mean)
Time per request:       158.221 [ms] (mean)
Time per request:       1.582 [ms] (mean, across all concurrent requests)
Transfer rate:          440.07 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   1.8      0     178
Processing:    67  155  46.4    147     879
Waiting:       67  155  46.4    147     879
Total:         67  156  46.5    147     880

Percentage of the requests served within a certain time (ms)
  50%    147
  66%    160
  75%    168
  80%    175
  90%    193
  95%    216
  98%    323
  99%    365
 100%    880 (longest request)

2)drds(5.6.29-TDDL-5.4.4-15864860)全局二级索引
执行的sql:
!!#0000ff SELECT uid,mobile FROM users WHERE mobile=’’;!!

joex@joexdembp ~ % ab -c 100 -n 10000 http://127.0.0.1/
This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 127.0.0.1 (be patient)
Completed 1000 requests
Completed 2000 requests
Completed 3000 requests
Completed 4000 requests
Completed 5000 requests
Completed 6000 requests
Completed 7000 requests
Completed 8000 requests
Completed 9000 requests
Completed 10000 requests
Finished 10000 requests


Server Software:        swoole-http-server
Server Hostname:        127.0.0.1
Server Port:            80

Document Path:          /
Document Length:        90 bytes

Concurrency Level:      100
Time taken for tests:   12.937 seconds
Complete requests:      10000
Failed requests:        0
Total transferred:      4490000 bytes
HTML transferred:       900000 bytes
Requests per second:    773.00 [#/sec] (mean)
Time per request:       129.366 [ms] (mean)
Time per request:       1.294 [ms] (mean, across all concurrent requests)
Transfer rate:          338.94 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0  17.5      0    1753
Processing:    26  128 180.5    100    1989
Waiting:       26  128 180.5     99    1989
Total:         31  129 181.4    100    1989

Percentage of the requests served within a certain time (ms)
  50%    100
  66%    116
  75%    128
  80%    136
  90%    169
  95%    243
  98%    313
  99%   1789
 100%   1989 (longest request)

||~ ab并发和请求数||数据库环境||执行时间(5次平均值)||QPS(每秒请求数)(5次平均值)||
||100并发,10000请求||drds(5.6.29-TDDL-5.3.7-15460044)|| 17.44 seconds||587||
||100并发,10000请求||drds(5.6.29-TDDL-5.4.4-15864860)全局二级索引|| 12.18 seconds||830||

[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-WTtqoiEW-1586768686639)(/tfl/captures/2020-04/tapd_38981207_base64_1586765666_50.png)]

[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-ntlWYqKS-1586768686639)(/tfl/captures/2020-04/tapd_38981207_base64_1586766337_18.png)]


3、 插入数据
1)drds(5.6.29-TDDL-5.3.7-15460044)主表+冗余表

joex@joexdembp ~ % ab -c 100 -n 10000 http://127.0.0.1/
This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 127.0.0.1 (be patient)
Completed 1000 requests
Completed 2000 requests
Completed 3000 requests
Completed 4000 requests
Completed 5000 requests
Completed 6000 requests
Completed 7000 requests
Completed 8000 requests
Completed 9000 requests
Completed 10000 requests
Finished 10000 requests


Server Software:        swoole-http-server
Server Hostname:        127.0.0.1
Server Port:            80

Document Path:          /
Document Length:        162 bytes

Concurrency Level:      100
Time taken for tests:   418.928 seconds
Complete requests:      10000
Failed requests:        8842
   (Connect: 0, Receive: 0, Length: 8842, Exceptions: 0)
Total transferred:      5230254 bytes
HTML transferred:       1630254 bytes
Requests per second:    23.87 [#/sec] (mean)
Time per request:       4189.277 [ms] (mean)
Time per request:       41.893 [ms] (mean, across all concurrent requests)
Transfer rate:          12.19 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.3      0       4
Processing:   845 4161 672.7   4231    7236
Waiting:      842 4161 672.7   4231    7236
Total:        846 4162 672.7   4232    7236

Percentage of the requests served within a certain time (ms)
  50%   4232
  66%   4491
  75%   4632
  80%   4725
  90%   4948
  95%   5122
  98%   5375
  99%   5656
 100%   7236 (longest request)

2)drds(5.6.29-TDDL-5.4.4-15864860)全局二级索引 主表

joex@joexdembp ~ % ab -c 100 -n 10000 http://127.0.0.1/
This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 127.0.0.1 (be patient)
Completed 1000 requests
Completed 2000 requests
Completed 3000 requests
Completed 4000 requests
Completed 5000 requests
Completed 6000 requests
Completed 7000 requests
Completed 8000 requests
Completed 9000 requests
Completed 10000 requests
Finished 10000 requests


Server Software:        swoole-http-server
Server Hostname:        127.0.0.1
Server Port:            80

Document Path:          /
Document Length:        57 bytes

Concurrency Level:      100
Time taken for tests:   10.948 seconds
Complete requests:      10000
Failed requests:        0
Total transferred:      4160000 bytes
HTML transferred:       570000 bytes
Requests per second:    913.39 [#/sec] (mean)
Time per request:       109.482 [ms] (mean)
Time per request:       1.095 [ms] (mean, across all concurrent requests)
Transfer rate:          371.06 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.4      0      11
Processing:    38  108  43.8     99     605
Waiting:       38  107  43.8     98     600
Total:         38  108  43.8     99     605

Percentage of the requests served within a certain time (ms)
  50%     99
  66%    111
  75%    120
  80%    126
  90%    148
  95%    178
  98%    264
  99%    313
 100%    605 (longest request)

||~ ab并发和请求数||数据库环境||执行时间(5次平均值)||QPS(每秒请求数)(5次平均值)||
||100并发,10000请求||drds(5.6.29-TDDL-5.3.7-15460044)|| 24 seconds||408.55||
||100并发,10000请求||drds(5.6.29-TDDL-5.4.4-15864860)全局二级索引|| 11.808 seconds||856||

[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-AqhVqhsc-1586768686640)(/tfl/captures/2020-04/tapd_38981207_base64_1586765507_87.png)]

[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-iQN9GcAt-1586768686640)(/tfl/captures/2020-04/tapd_38981207_base64_1586765286_61.png)]

####结论

目前的结论是基于数据量在10W左右

1、在查询(SELECT * )查询所有列时:直接查询主表-未建全局二级索引的执行时间和QPS是 最优的 ;查询查询主表-建立全局二级索引的执行时间和QPS次之,应该是因为查询了索引表后进行了回表;而自建冗余表索引+主表缺失列回查执行和全局二级索引原理类似,执行效率也是差不多。
2、在查询 (select uid mobile)全局二级索引/自写冗余索引表(不回表)时:全局二级索引比自写冗余索引表的优势明显。
3、插入数据:主表+写冗余索引表和全局二级索引的对比,全局二级索引优势更加明显。
4、GSI综合比较下来比自写冗余索引表方式效率更优,但考虑目前GSI在DML、DDL下有一定的限制与约定,所以在替换自写冗余索引表的时候得评估下限制与约定是否会造成影响。

你可能感兴趣的:(sql总结)