Hi there! First of all I want to thank you for your time and efforts about this project.
I am Software Engineer with almost 3 years experience, most of the time I work with Java related technologies. Recently I have started to consider possibility to contribute to Flink. For begin I chose this issue: https://issues.apache.org/ jira/browse/FLINK-9432. After implementation I have faced with an interesting question. When I was trying to decide what tests to create for the function DECADE in class org/apache/flink/table/expressions/validation/ScalarFunctionsValidationTest.scala I've figured out that such functions as CENTURY and MILLENNIUM work with TIME type without problems. Here an examples: EXTRACT(CENTURY FROM TIME '00:00:00') - returns 0 EXTRACT(MILLENNIUM FROM TIME '00:00:00') - returns 0 It's strange by my opinion, time is not date and how we can extract such things from that. Meanwhile when I try to use similar logic in calcite, error is occured. Here an example: SELECT EXTRACT(CENTURY FROM TIME '00:00:00'); throws `java.lang.AssertionError: unexpected TIME` Is it necessary to create separate issue for that?
