SqlNode转化成对应的Operation(RelNode)在类org.apache.flink.table.planner.operations.SqlToOperationConverter中完成，代码如下

    1.     // org.apache.flink.table.planner.operations.SqlToOperationConverter
    2.     /**
    3.      * This is the main entrance for executing all kinds of DDL/DML {@code SqlNode}s, different
    4.      * SqlNode will have it's implementation in the #convert(type) method whose 'type' argument
    5.      * is subclass of {@code SqlNode}.
    6.      *
    7.      * @param flinkPlanner FlinkPlannerImpl to convertCreateTable sql node to rel node
    8.      * @param catalogManager CatalogManager to resolve full path for operations
    9.      * @param sqlNode SqlNode to execute on
    10.      */
    11.     public static Optional<Operation> convert(
    12.             FlinkPlannerImpl flinkPlanner,
    13.             CatalogManager catalogManager,
    14.             SqlNode sqlNode) {
    15.         // validate the query
    16.         final SqlNode validated = flinkPlanner.validate(sqlNode);
    17.         SqlToOperationConverter converter = new SqlToOperationConverter(flinkPlanner, catalogManager);
    18.         if (validated instanceof SqlCreateTable) {
    19.             return Optional.of(converter.convertCreateTable((SqlCreateTable) validated));
    20.         } else if (validated instanceof SqlDropTable) {
    21.             return Optional.of(converter.convertDropTable((SqlDropTable) validated));
    22.         } else if (validated instanceof SqlAlterTable) {
    23.             return Optional.of(converter.convertAlterTable((SqlAlterTable) validated));
    24.         } else if (validated instanceof SqlCreateFunction) {
    25.             return Optional.of(converter.convertCreateFunction((SqlCreateFunction) validated));
    26.         } else if (validated instanceof SqlAlterFunction) {
    27.             return Optional.of(converter.convertAlterFunction((SqlAlterFunction) validated));
    28.         } else if (validated instanceof SqlDropFunction) {
    29.             return Optional.of(converter.convertDropFunction((SqlDropFunction) validated));
    30.         } else if (validated instanceof RichSqlInsert) {
    31.             return Optional.of(converter.convertSqlInsert((RichSqlInsert) validated));
    32.         } else if (validated instanceof SqlUseCatalog) {
    33.             return Optional.of(converter.convertUseCatalog((SqlUseCatalog) validated));
    34.         } else if (validated instanceof SqlUseDatabase) {
    35.             return Optional.of(converter.convertUseDatabase((SqlUseDatabase) validated));
    36.         } else if (validated instanceof SqlCreateDatabase) {
    37.             return Optional.of(converter.convertCreateDatabase((SqlCreateDatabase) validated));
    38.         } else if (validated instanceof SqlDropDatabase) {
    39.             return Optional.of(converter.convertDropDatabase((SqlDropDatabase) validated));
    40.         } else if (validated instanceof SqlAlterDatabase) {
    41.             return Optional.of(converter.convertAlterDatabase((SqlAlterDatabase) validated));
    42.         } else if (validated.getKind().belongsTo(SqlKind.QUERY)) {
    43.             return Optional.of(converter.convertSqlQuery(validated));
    44.         } else {
    45.             return Optional.empty();
    46.         }
    47.     }