Tianshi Zhu created FLINK-20986:
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Summary: GenericTypeInfo equality issue
Key: FLINK-20986
URL: https://issues.apache.org/jira/browse/FLINK-20986
Project: Flink
Issue Type: Bug
Affects Versions: 1.12.0
Reporter: Tianshi Zhu
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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