[#3002] fix(jdbc-mysql): Fix MySQL list tables bugs.

[yuqi1129]

What changes were proposed in this pull request?

Set the connection database to the database passed by the method when getting the JDBC connection.

Why are the changes needed?

connection.getSchema() is null for MySQL and thus will cause the problem that list operation will get all tables in the MySQL instance NOT a specific database.

Fix: #3002

Does this PR introduce any user-facing change?

N/A.

How was this patch tested?

New UT was added.

[jerryshao]

Do we have a similar problem in PG and Doris?

[FANNG1]

Could you verify whether the problem still exists if getConnection using setSchema(xx) not setCatalog(xx)?

    Connection getConnection(String catalog) {
       Connection connection = dataSource.getConnection();
       connection.setCatalog(catalog);
    }

[FANNG1]

noticed that getTables using connection.getSchema() to retrieve tables, the total JDBC logic is muddledness ：（

  protected ResultSet getTables(Connection connection) throws SQLException {
    final DatabaseMetaData metaData = connection.getMetaData();
    String databaseName = connection.getSchema();
    return metaData.getTables(databaseName, databaseName, null, JdbcConnectorUtils.getTableTypes());
  }

[yuqi1129]

noticed that getTables using connection.getSchema() to retrieve tables, the total JDBC logic is muddledness ：（

  protected ResultSet getTables(Connection connection) throws SQLException {
    final DatabaseMetaData metaData = connection.getMetaData();
    String databaseName = connection.getSchema();
    return metaData.getTables(databaseName, databaseName, null, JdbcConnectorUtils.getTableTypes());
  }

I have removed the line String databaseName = connection.getSchema();.

Root cause of this problem: String databaseName = connection.getSchema(); is always null.
please review it again.

[yuqi1129]

Could you verify whether the problem still exists if getConnection using setSchema(xx) not setCatalog(xx)?

    Connection getConnection(String catalog) {
       Connection connection = dataSource.getConnection();
       connection.setCatalog(catalog);
    }

It's not work to use setSchema(xx);

[FANNG1]

Could you verify whether the problem still exists if getConnection using setSchema(xx) not setCatalog(xx)?

    Connection getConnection(String catalog) {
       Connection connection = dataSource.getConnection();
       connection.setCatalog(catalog);
    }

It's not work to use setSchema(xx);

when you test do you remove String databaseName = connection.getSchema();

[yuqi1129]

Could you verify whether the problem still exists if getConnection using setSchema(xx) not setCatalog(xx)?

    Connection getConnection(String catalog) {
       Connection connection = dataSource.getConnection();
       connection.setCatalog(catalog);
    }

It's not work to use setSchema(xx);

when you test do you remove String databaseName = connection.getSchema();

No, the method:

  protected ResultSet getTables(Connection connection) throws SQLException {
    final DatabaseMetaData metaData = connection.getMetaData();
    String databaseName = connection.getSchema();

    // We need the database name here.
    return metaData.getTables(databaseName, databaseName, null, JdbcConnectorUtils.getTableTypes());
  }

The value of the schema name must be passed as a method parameter, otherwise we cannot remove it.

[yuqi1129]

Do we have a similar problem in PG and Doris?

Yes, I have checked, the changes in the PR is in the module jdbc-common and will fix a similar issue in all JDBC catalogs.

[jerryshao]

@yuqi1129 can you please move forward this PR?

[yuqi1129]

@yuqi1129 can you please move forward this PR?

Yeah, A related PR has just been merged, I will rebase it soon.

[yuqi1129]

@danhuawang
Could you kindly verify if the performance test has returned to normal since today? It appears that this issue has been resolved by #3316.

[yuqi1129]

@danhuawang confirmed that the problem has been resolved by #3316 and the PR will be temporarily closed.