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https://issues.apache.org/jira/browse/FLINK-21425?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17288138#comment-17288138
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Jark Wu commented on FLINK-21425:
---------------------------------

Hi [~Suxing Lee], Flink doesn't support implict type conversion currently. So 
this is a new feature. 

Implicit type conversion is a big topic needs to be discussed comprehensively 
and publically. String <-> Int is an important and unclear conversion, we 
should also need to consider other conversions too. Actually, we already have a 
FLIP [1] under discussion. 

Therefore, I suggest to close this issue, and focus on the discussion of 
FLIP-154 first. FLIP-154 should cover your problems.

Btw, in your PR, you modified {{flink-table-planner}} module. However, it is a 
legecy planner which we don't maintain anymore (unless critical bugs). New 
features should only be supported in {{flink-table-planner-blink}} module.

[1]: 
https://cwiki.apache.org/confluence/display/FLINK/FLIP-154%3A+SQL+Implicit+Type+Coercion

> Incorrect implicit conversions in equals and notEquals filter predicates lead 
> to not correctly evaluated by Table API
> ---------------------------------------------------------------------------------------------------------------------
>
>                 Key: FLINK-21425
>                 URL: https://issues.apache.org/jira/browse/FLINK-21425
>             Project: Flink
>          Issue Type: Bug
>          Components: Table SQL / Planner
>    Affects Versions: 1.12.1
>            Reporter: Suxing Lee
>            Priority: Major
>              Labels: pull-request-available
>
> Equality and NotEquality filter predicates do not work on Tables when 
> leftTerm and rightTerm type is mismatch(one is string ,another is integer)
> column : a,b,c
> the test data is as follows :
> 1,1L,"Hi"
> 2,2L,"Hello"
> 3,2L,"Hello world"
> for query : SELECT a,b,c FROM table WHERE a <> '1'
> The correct implicit conversion expected from the query result is: 
> 2,2L,"Hello"
> 3,2L,"Hello world"
> But in fact the current query result is:
> 1,1L,"Hi"
> 2,2L,"Hello"
> 3,2L,"Hello world"



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