[PDGGK]

Description

Since #872, every TSDataType constant holds a SingleValueCaster and an ArrayCaster, set to lambdas that are not serializable (TSDataType.java:129-:130 on develop). Java serializes an enum constant only by its name, so Java serialization is not affected. Flink's ClosureCleaner, however, serializes every non-static, non-transient field of the objects that a function holds, including the fields of enum constants, and rejects the function when one of them fails.

I ran into this while raising iotdb-extras to TsFile 2.5.0. RowTsFileInputFormatIntegrationTest.testStreamExecution of its Flink TsFile connector (Flink 1.17.1) passes with TsFile 2.4.0 and fails with 2.5.0:

org.apache.flink.api.common.InvalidProgramException: org.apache.tsfile.enums.TSDataType$$Lambda$96/0x000000d80109d000@3ccb12d is not serializable. The object probably contains or references non serializable fields.
	at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:164)
	...
	at org.apache.flink.streaming.api.environment.StreamExecutionEnvironment.createInput(StreamExecutionEnvironment.java:1784)

The input format reaches a TSDataType through TsFileInputFormat.config → TSFileConfig.timeSeriesDataType, and ClosureCleaner recurses into every field that is neither static nor transient (needsRecursion in Flink 1.17). Until a release has this change, a job on 2.5.0 can avoid it with env.getConfig().setClosureCleanerLevel(ExecutionConfig.ClosureCleanerLevel.TOP_LEVEL).

Change

Both fields are now transient. Nothing reads them after deserialization, because deserializing an enum constant returns the existing constant.

Verification

• New TSDataTypeSerializationTest in java/common:
  • every non-static, non-transient field of every constant can be serialized. This fails before the change with NotSerializableException: org.apache.tsfile.enums.TSDataType$$Lambda...;
  • Java serialization still returns the same constant.
• All 7 tests in java/common pass, and so do TypeCastTest and TsPrimitiveTypeTest in java/tsfile. spotless:check passes.
• I applied the change to v2.5.0 and installed it locally as 2.5.0-tsfix. With it, all 8 tests of the iotdb-extras flink-tsfile-connector pass, including testStreamExecution.

[ColinLeeo]

LGTM