Sequence Query and CircuitBreaker in ShardingSphere

[xuejmnet]

Hello I'm ShardingCore Author，this lib is c# for sharding,.

i have some idea want share,i think it's useful.

• sequence query
• circuit breaker

sequence query with order

i'm create sharding table and use time strategy like sharding by month or day ....

sharding logic table name order,sharding column time

order_202201,order_202202,order_202203,order_202204.

select * from order  order by time desc limit 1

now

parallel with max connections thread

select * from order_202201 order by time desc limit 1
select * from order_202202 order by time desc limit 1
select * from order_202203 order by time desc limit 1
select * from order_202204 order by time desc limit 1

then merge in memory

i think if shardingsphere can configure sequence eg. sharding tail comparer,

config.add("time",comparer)
config.add("id",comparer) if id is snowflakeid

optimize

we can use independence config for max connections eg. config.addsequenceconnectons(1)

result=select * from order_202204 order by time desc limit 1
if(result!=null){
  circuit breaker
}
result=select * from order_202203 order by time desc limit 1
if(result!=null){
  circuit breaker
}
result=select * from order_202202 order by time desc limit 1
if(result!=null){
  circuit breaker
}
select * from order_202201 order by time desc limit 1

circuit breaker

select max(time) from order 

now

select max(time) from order_202201 
select max(time) from order_202202 
select max(time) from order_202203
select max(time) from order_202204

then in memory merge calc max time in list

optimize

result=select max(time) from order_202204
if(result!=null){
  circuit breaker
}
result=select max(time) from order_202203
if(result!=null){
  circuit breaker
}
result=select max(time) from order_202202 
if(result!=null){
  circuit breaker
}
select max(time) from order_202201 

[xuejmnet]

idea chinese blog

[xuejmnet]

i dont know now shardingsphere use which tails comparer in source code, i'm not found resort tails before partations,in sequence i think it's very useful.

if i'm set maxqueryconnections=1

select * from order  order by time desc limit 1

now

select * from order_202201 order by time desc limit 1
select * from order_202202 order by time desc limit 1
select * from order_202203 order by time desc limit 1
select * from order_202204 order by time desc limit 1

we should wait serial query 4 times,i think random sort table tail is bad,some time we should use sequence sort with table tail,and only add circuit breaker we can give up other query

[terrymanu]

Hi @xuejmnet Thank you for the suggestion, I will study it when I am free.

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