Shuyi Chen created FLINK-13372:
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Summary: Timestamp conversion bug in non-blink Table/SQL runtime
Key: FLINK-13372
URL:
https://issues.apache.org/jira/browse/FLINK-13372 Project: Flink
Issue Type: Bug
Components: Table SQL / Runtime
Affects Versions: 1.8.1, 1.8.0, 1.7.2, 1.6.4, 1.6.3
Reporter: Shuyi Chen
Assignee: Shuyi Chen
Currently, in the non-blink table/SQL runtime, Flink used SqlFunctions.internalToTimestamp(long v) from Calcite to convert event time (in long) to java.sql.Timestamp.
{code:java} public static Timestamp internalToTimestamp(long v) { return new Timestamp(v - (long)LOCAL_TZ.getOffset(v)); } {code}
However, as discussed in the recent Calcite mailing list, SqlFunctions.internalToTimestamp() assumes the input timestamp value is in the current JVM’s default timezone (which is unusual), NOT milliseconds since epoch. And SqlFunctions.internalToTimestamp() is used to convert timestamp value in the current JVM’s default timezone to milliseconds since epoch, which java.sql.Timestamp constructor takes. Therefore, the results will not only be wrong, but change if the job runs in machines on different timezones as well.
Here is an example, if the user input value is 0 (00:00:00 UTC on 1 January 1970), and the table/SQL runtime runs in a machine with in PST (UTC-8), the output sql.Timestamp after SqlFunctions.internalToTimestamp() will become 28800000 millisec since epoch (08:00:00 UTC on 1 January 1970); And if the table/SQL runtime runs in a machine with in EST (UTC-5), the output sql.Timestamp after SqlFunctions.internalToTimestamp() will become 18000000 millisec since epoch (05:00:00 UTC on 1 January 1970).
Currently, there are unittests to test the table/SQL API event time input/output (e.g., GroupWindowITCase.testEventTimeTumblingWindow() and SqlITCase.testDistinctAggWithMergeOnEventTimeSessionGroupWindow()). They now all passed because we are comparing the string format of the time which ignores timezone. If you step into the code, the actual java.sql.Timestamp value is wrong and change as the tests run in different timezone (e.g., one can use -Duser.timezone=PST to change the current JVM’s default timezone)
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