terrymanu commented on issue #37711:
URL:
https://github.com/apache/shardingsphere/issues/37711#issuecomment-3737767421
Issue understanding: On ShardingSphere-JDBC 5.5.2 (MySQL) you execute CREATE
TEMPORARY TABLE tmp_sys_user AS ... via MyBatis-Plus. After the DDL,
ShardingSphere triggers metadata refresh and throws Load actual table metadata
'tmp_sys_user' failed.
Root cause: The DDL metadata refresher opens a new physical connection to
fetch table metadata and is designed for persistent tables. Session-scoped
temporary tables are only visible on the connection that created them, so the
refresher cannot see tmp_sys_user,
GenericSchemaBuilder returns empty, and the assert in
CreateTableStatementSchemaRefresher fails. This is a current limitation rather
than a bug in persistent-table handling.
Problem analysis: The flow is DDL execution →
CreateTableStatementSchemaRefresher.refresh → GenericSchemaBuilder.build to
reload table definition. Because the refresh uses a separate connection, the
temporary table is invisible, actualTableMetaData is empty, and the check
raises the exception. ShardingSphere’s metadata management tracks logical
databases against real persistent objects; session-level temporary tables are
out of scope, so they are not supported in the metadata refresh logic.
Conclusion: This behavior reflects the present design: ShardingSphere-JDBC
does not support metadata refresh for session-scoped temporary tables. Please
avoid relying on ShardingSphere to manage temporary tables. If you still see
this when everything happens on the
exact same physical connection, please share database type/version, your
rule/data source configuration, and the full ShardingSphere log stack to
confirm there are no other rule interactions.
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