liugddx commented on issue #2861:
URL:
https://github.com/apache/incubator-seatunnel/issues/2861#issuecomment-1331703746
Yeah, but not all primary keys are numeric and that's something to think
about
Best Regards
liugddx
***@***.***
------------------ Original ------------------
From: ***@***.***>;
Date: 2022年11月30日(星期三) 下午2:26
To: ***@***.***>;
Cc: ***@***.***>; ***@***.***>;
Subject: Re: [apache/incubator-seatunnel] [Feature][Discuss] Uneven data
distribution. (Issue #2861)
https://shardingsphere.apache.org/document/current/en/dev-manual/sharding/
Regarding the jdbc data source, most of the primary keys may be data such as
uuid. We can't just be restricted to numeric types,hash mode is a better
sharding method, of course we can provide more sharding methods.
Hash maybe have some problem in single database, the each split read data
may discontinuous, the preformance not good. And how to use sql to describe it
also is a problem.
SQL needs to be in the dialect and needs to be tested and optimized for
performance.
select * from test where id mod 2=1
Seem like every split will scan all data.
This is related to the storage form of the data, may or may not. But often
there will be some performance loss
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