how to build sql from RelBuild without schema info?

i want to generate sql use calcite. like this

org.apache.calcite.rel.rel2sql.RelToSqlConverterTest#testAntiJoin

final FrameworkConfig frameworkConfig = Frameworks.newConfigBuilder()
       .parserConfig(SqlParser.Config.DEFAULT)
//       .defaultSchema(schema)
       .build();

final RelBuilder builder = RelBuilder.create(frameworkConfig);

final RelBuilder builder = relBuilder();
final RelNode root = builder
       .scan("DEPT")
        .scan("EMP")
        .join(
            JoinRelType.ANTI, builder.equals(
              builder.field(2, 1, "DEPTNO"),
              builder.field(2, 0, "DEPTNO")))
        .project(builder.field("DEPTNO"))
        .build();

but if i don't set the schema, the exception table not found will be throw. is there any way to generate sql without schema info.

the aim is generate sql. just generate sql.

reply for first answer. because comment character length limit.

My scenario is Business Intelligence. DataSource can be many, such as Hive, ClickHouse, and so on. And there are many tables. I also need to dynamically delete or add datasource. So I don't think it's appropriate for Calcite to be aware of all the data sources. I have two more questions:

How to create 'free-standing' table objects as you said
Check whether SqlNode can be used to do this. for example:

        SqlIdentifier from = new SqlIdentifier("testTable", SqlParserPos.QUOTED_ZERO);
        SqlNode[] nodes = new SqlNode[2];
        nodes[0] = new SqlIdentifier("a", SqlParserPos.QUOTED_ZERO);
        nodes[1] = SqlLiteral.createExactNumeric("1", SqlParserPos.QUOTED_ZERO);
        SqlNode where = new SqlBasicCall(SqlStdOperatorTable.EQUALS, nodes, SqlParserPos.QUOTED_ZERO);
        SqlIdentifier selectNode = new SqlIdentifier("a", SqlParserPos.QUOTED_ZERO);
        SqlSelect select = new SqlSelect(SqlParserPos.QUOTED_ZERO, SqlNodeList.EMPTY,
                new SqlNodeList(Arrays.asList(selectNode), SqlParserPos.QUOTED_ZERO),
                from,
                where,
                null,
                null,
                null,
                null,
                null,
                null,
                null);
        SqlString sqlString = select.toSqlString(CalciteSqlDialect.DEFAULT);
        System.out.println(sqlString.getSql());

Solution

Only one method in RelBuilder uses a RelOptSchema: scan(String...) (and its variant Scan(Iterable<String>)). Which makes sense when you consider that the purpose of RelOptSchema is as a directory service, converting a table name (or table path, consisting of a table name qualified with catalog and/or schema names) into a RelOptTable object.

If you have 'free-standing' table objects that are not accessed via a namespace then you can create TableScan relational expressions directly and then call RelBuilder.push(RelNode) to add them to the stack. Since you never call RelBuilder.scan you can create RelBuilder with a null RelOptSchema.

But in your case, it looks as if you don't have free-standing table objects. That's a problem for Calcite, because it needs to know that your "EMP" table has a field called "DEPTNO" and it has type INTEGER.

So I suggest that you create a 'virtual' schema that contains type information but is not necessarily backed by real tables. The MockCatalogReader class, used in several of Calcite's tests, is a good example to follow.