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https://issues.apache.org/jira/browse/FLINK-20986?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tianshi Zhu updated FLINK-20986:
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Component/s: Table SQL / Planner
Runtime / REST
> 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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