[jira] [Commented] (FLINK-20986) GenericTypeInfo equality issue

["Jark Wu (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-20986?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17265734#comment-17265734 ] 

Jark Wu commented on FLINK-20986:
---------------------------------

Is it possible to reproduce the problem using a Table API? If yes, could you share one? That would help to fix the problem. 

> GenericTypeInfo equality issue
> ------------------------------
>
>                 Key: FLINK-20986
>                 URL: https://issues.apache.org/jira/browse/FLINK-20986
>             Project: Flink
>          Issue Type: Bug
>          Components: Runtime / REST, Table SQL / Planner
>    Affects Versions: 1.12.0
>            Reporter: Tianshi Zhu
>            Priority: Major
>
> When trying to use Flink REST api to run a job that uses Flink table api with blink planner, we encountered an issue about `Incompatible types of expression and result type.` from org.apache.flink.table.planner.codegen.ExprCodeGenerator$$anonfun$generateResultExpression$1.apply(ExprCodeGenerator.scala:311). This issue only happens after the first request has been handled successfully.
>  
> After digging, we found that there are two static caches used inside calcite's
> RelDataTypeFactoryImpl (
> https://github.com/apache/calcite/blob/d9a81b88ad561e7e4cedae93e805e0d7a53a7f1a/core/src/main/java/org/apache/calcite/rel/type/RelDataTypeFactoryImpl.java#L352-L376
> ), which will remember the types they have seen. The `canonize` method is called from FlinkTypeFactory 
> https://github.com/apache/flink/blob/89f9dcd70dc3a1433055e17775b2b2a2c796ca94/flink-table/flink-table-planner-blink/src/main/scala/org/apache/flink/table/planner/calcite/FlinkTypeFactory.scala#L292
>  
> This causes problem for us because in our experience, we have seen GenericTypeInfo<T> containing different Class<T> instances in two different REST requests, and they do not equal, because [https://github.com/apache/flink/blob/89f9dcd70dc3a1433055e17775b2b2a2c796ca94/flink-core/src/main/java/org/apache/flink/api/java/typeutils/GenericTypeInfo.java#L124] is using object equality. After `canonize`, the GenericTypeInfo for other REST requests would be changed to the GenericTypeInfo used for the first REST request, which is cached in RelDataTypeFactoryImpl. And this leads to the incompatible type error mentioned above.
>  
> I want to propose using class name for equality comparison inside GenericTypeInfo, and change hashCode method accordingly.
>  



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