wangzhigang1999 commented on code in PR #7419:
URL: https://github.com/apache/kyuubi/pull/7419#discussion_r3152120945
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externals/kyuubi-jdbc-engine/src/main/scala/org/apache/kyuubi/engine/jdbc/dialect/JdbcDialect.scala:
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@@ -82,6 +82,20 @@ abstract class JdbcDialect extends SupportServiceLoader with
Logging {
def getSchemaHelper(): SchemaHelper
+ /**
+ * Switch the current database on the backend connection.
+ *
+ * Called during session open when the client specified a database in the
connection URL
+ * (populated by the Hive JDBC driver into `USE_DATABASE`). Dialects that
support an
+ * in-session database context switch (e.g. MySQL's `USE db`) should
override this and
+ * return `true` on success; the default is a no-op that returns `false`,
meaning the
+ * backend has no notion of "current database" that applies to this session.
+ *
+ * The return value is used by `JdbcOperationManager` to decide whether the
requested
+ * database can be treated as the effective schema filter for metadata
operations.
+ */
+ def setCurrentDatabase(connection: Connection, database: String): Boolean =
false
Review Comment:
Update — went with **Option B** and pushed it as ff518412e.
`MySQLDialect.setCurrentDatabase` now calls
`connection.setCatalog(database)` followed by `connection.setSchema(database)`
instead of executing `USE` ourselves. `JdbcDialect`'s default stays a no-op
returning `false`, and no other dialect is touched.
Why B over A:
- Goes through JDBC standard API, addressing the spirit of your review — no
more hand-rolled SQL, no backtick escaping concerns.
- Engages the driver's internal hooks (`useLocalSessionState` cache,
`ConnectionLifecycleInterceptor`) so connection state stays coherent.
- Double-call cost is effectively zero: under any `databaseTerm`, the
non-matching branch is `if (false) return` with no network IO.
- Functionally equivalent for MySQL / StarRocks / Doris — verified locally
with DBeaver: logs show `catalog=null → catalog=doctor`, confirming
`setCatalog` actually sends `COM_INIT_DB`.
Why I didn't extend `setSchema` to the default impl for other dialects:
Phoenix / Impala drivers are likely to throw `SQLFeatureNotSupportedException`
from `setSchema`, which would regress session open. Keeping the change scoped
to MySQL family.
Also added three StarRocks regression tests covering URL-scoped getTables,
no-filter when URL has no db, and session-open failure on a non-existent db.
PTAL.
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