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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