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https://issues.apache.org/jira/browse/FLINK-20986?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17271285#comment-17271285
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Tianshi Zhu commented on FLINK-20986:
-------------------------------------
[~twalthr] Thanks for helping on this issue. feel free to take over. We could
also just skip calling canonize in FlinkTypeFactory. But I'm not super
confident when we should or should not call it. Or any performance impact. Also
not sure how to override the other canonize method `protected RelDataType
canonize(final StructKind kind, final List<String> names, final
List<RelDataType> types, final boolean nullable)`:
[https://github.com/apache/calcite/blob/d9a81b88ad561e7e4cedae93e805e0d7a53a7f1a/core/src/main/java/org/apache/calcite/rel/type/RelDataTypeFactoryImpl.java#L364.]
In my own experience, I have to clear both caches to make the REST API work.
> GenericTypeInfo equality issue
> ------------------------------
>
> Key: FLINK-20986
> URL: https://issues.apache.org/jira/browse/FLINK-20986
> Project: Flink
> Issue Type: Bug
> Components: Table SQL / Planner
> Affects Versions: 1.12.0
> Reporter: Tianshi Zhu
> Priority: Major
> Labels: pull-request-available
>
> 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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