wangzhigang1999 commented on code in PR #7419:
URL: https://github.com/apache/kyuubi/pull/7419#discussion_r3154003255
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externals/kyuubi-jdbc-engine/src/main/scala/org/apache/kyuubi/engine/jdbc/dialect/MySQLDialect.scala:
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@@ -122,6 +150,16 @@ class MySQLDialect extends JdbcDialect {
query.toString()
}
+ override def setSchema(conn: Connection, schema: String): Unit = {
+ // mysql-connector-j makes setCatalog/setSchema mutually exclusive based
on the
+ // `databaseTerm` connection property: with the default CATALOG,
setCatalog issues
+ // COM_INIT_DB and setSchema is a silent no-op; with SCHEMA it is the
inverse.
+ // Calling both means exactly one fires regardless of how the user
configured the
+ // URL. StarRocksDialect / DorisDialect inherit this via MySQLDialect.
+ conn.setCatalog(schema)
+ conn.setSchema(schema)
Review Comment:
Good point to think through. The dual `setCatalog` + `setSchema` is safe
because mysql-connector-j uses its `databaseTerm` connection property to select
which of the two calls actually switches the session database; the other call
returns without effect for that mode. So no matter how the user configured the
URL, the StarRocks/Doris server only ever receives one "switch database"
command, never two.
Verified by black-box testing — under the default `CATALOG` setting, calling
`setSchema` alone does not change the session database; under `SCHEMA`, calling
`setCatalog` alone does not. Calling both is the safe path. The behavior is
consistent with what the [MySQL Connector/J reference
manual](https://dev.mysql.com/doc/connector-j/en/connector-j-reference-configuration-properties.html)
documents about the property.
The server treats the resulting "switch database" as exactly that — it does
**not** treat it as "switch catalog" (catalog switching on StarRocks/Doris is a
separate `SET CATALOG` SQL statement, not something the MySQL protocol
exposes). The name we pass in comes from `USE_DATABASE`, which the Hive JDBC
driver parses out of the URL path. The Hive URL syntax has no concept of
catalog, so this name is always a database in the current (default) catalog.
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