[JDBC, Client] DateTime logic should be in the client

[chernser]

Description

Date/Time data types are most complex in terms of working with them. First - there are different classes in Java that handles time. Second - conversion between them may lead to errors in data because of many parameters should be cared about. Maintaining good support for these types requires code to be well tested and coherent. We need to move all related code to the client.

Data Type Match to Java Class

ClickHouse Type	Java Class
Date	ZonedDateTime
Date32	ZonedDateTime
DateTime	ZonedDateTime
DateTime64	ZonedDateTime
Time	Integer
Time64	Long

Most of date/time types are represented with ZonedDateTime to carry timezone information. Time and Time64 are represented as Integer/Long because they have no timezone information.

JDBC Use Cases

There are several usecases in the JDBC driver that require ClickHouse data type conversion to one of Java Date/Time classes.

PreparedStatement interface has methods that require the conversion:

• setTime(Time, Calendar)
• setTimestamp(Timestamp, Calendar)
• setDate(Date, Calendar)
• setObject(Object, SQLType) - there are can be anything Instant, LocalTime event a string?.

ResultSet interface has next methods that require the conversion:

• getDate(int columnIndex, Calendar cal)
• getTime(int columnIndex, Calendar cal)
• getTimestamp(int columnIndex, Calendar cal)

Other Use Cases

• Formatting Java Date/Time classes into a string suitable for DB

[enqueue]

Also check magic in PreparedStatementImpl.

[chernser]

@enqueue I would appreciate any help with this issue: ideas, code, tests. Goal is to cover this problem as much as we can.

As the first step we need to fill use-case, I think. To understand how better to approach the problem:

• some cases is a good utility code
• some cases can be only covered by documentation.

[enqueue]

@chernser Thank you. I am going to write down some assumptions and tests first. We can then discuss them.