terrymanu commented on issue #28858:
URL:
https://github.com/apache/shardingsphere/issues/28858#issuecomment-3642523219
## Problem Understanding
- Using MySQL Connector/J 8 against ShardingSphere-Proxy, selecting a YEAR
column returns java.sql.Date even when yearIsDateType=false, instead of Short
as expected.
## Root Cause
- Proxy reuses backend JDBC metadata columnType for result metadata. The
backend reports YEAR as Types.DATE, and ResponsePacketBuilder maps that to
MySQL protocol type DATE (0x0a) instead of YEAR (0x0d). The driver therefore
never applies the yearIsDateType behavior.
## Analysis
- Native MySQL marks YEAR columns as protocol type YEAR (0x0d), which lets
Connector/J honor yearIsDateType=false and return Short (official doc for the
property:
https://dev.mysql.com/doc/connector-j/8.0/en/connector-j-reference-configuration-properties.html
(https://
dev.mysql.com/doc/connector-j/8.0/en/connector-j-reference-configuration-properties.html)).
- In Proxy, MySQLQueryHeaderBuilder passes the JDBC columnType (seen as
Types.DATE) to ResponsePacketBuilder; MySQLBinaryColumnType.valueOfJDBCType has
no YEAR branch, so it always uses DATE. This protocol mismatch prevents the
driver’s YEAR handling.
## Conclusion / Fix Suggestion
- This is a Proxy type-mapping gap. When building column definitions,
detect YEAR (e.g., via columnTypeName == "YEAR" or an explicit YEAR metadata
check) and map it to MySQL protocol type YEAR (0x0d) rather than DATE. That
aligns Proxy with native MySQL and lets
yearIsDateType=false work.
- Temporary workaround: CAST(t_year AS UNSIGNED) in SQL or use getShort on
the client, but the correct fix is the mapping change.
- We warmly welcome a PR to implement and test this mapping so behavior
matches native MySQL. Happy to help review or validate!
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