presto-main/src/main/java/io/prestosql/connector/system/jdbc/SchemaJdbcTable.java/SchemaJdbcTable/cursor
class SchemaJdbcTable:    @Override
    public RecordCursor cursor(ConnectorTransactionHandle transactionHandle, ConnectorSession connectorSession, TupleDomain<Integer> constraint)
    {
        Session session = ((FullConnectorSession) connectorSession).getSession();
        Optional<String> catalogFilter = FilterUtil.stringFilter(constraint, 1);

        Builder table = InMemoryRecordSet.builder(METADATA);
        for (String catalog : filter(listCatalogs(session, metadata, accessControl).keySet(), catalogFilter)) {
            for (String schema : listSchemas(session, metadata, accessControl, catalog)) {
                table.addRow(schema, catalog);
            }
        }
        return table.build().cursor();
    }