Presto执行计划 - 分发Statement到不同的QueryExecution

 preparedQuery = queryPreparer.prepareQuery(session, query);
// .... 
DispatchQuery dispatchQuery = dispatchQueryFactory.createDispatchQuery(
                    session,
                    query,
                    preparedQuery,
                    slug,
                    selectionContext.getResourceGroupId());

@Override
    public DispatchQuery createDispatchQuery(
            Session session,
            String query,
            PreparedQuery preparedQuery,
            Slug slug,
            ResourceGroupId resourceGroup)
    {
        WarningCollector warningCollector = warningCollectorFactory.create();
        QueryStateMachine stateMachine = QueryStateMachine.begin(
                query,
                preparedQuery.getPrepareSql(),
                session,
                locationFactory.createQueryLocation(session.getQueryId()),
                resourceGroup,
                isTransactionControlStatement(preparedQuery.getStatement()),
                transactionManager,
                accessControl,
                executor,
                metadata,
                warningCollector,
                StatementUtils.getQueryType(preparedQuery.getStatement().getClass()));

        // It is important that `queryCreatedEvent` is called here. Moving it past the `executor.submit` below
        // can result in delivering query-created event after query analysis has already started.
        // That can result in misbehaviour of plugins called during analysis phase (e.g. access control auditing)
        // which depend on the contract that event was already delivered.
        //
        // Note that for immediate and in-order delivery of query events we depend on synchronous nature of
        // QueryMonitor and EventListenerManager.
        queryMonitor.queryCreatedEvent(stateMachine.getBasicQueryInfo(Optional.empty()));

        ListenableFuture<QueryExecution> queryExecutionFuture = executor.submit(() -> {
          	// 在这里根据 statement 的类别生成不同的QueryExecution
          	// 一种是：DataDefinitionExecution，创建视图/创建表/重命名列之类的DDL操作使用这个执行器
          	// 一种是：SqlQueryExecution，查询/show操作/use//insert/delete 之类的操作使用这个执行器
          	// 具体见后面的表格
            QueryExecutionFactory<?> queryExecutionFactory = executionFactories.get(preparedQuery.getStatement().getClass());
            if (queryExecutionFactory == null) {
                throw new TrinoException(NOT_SUPPORTED, "Unsupported statement type: " + preparedQuery.getStatement().getClass().getSimpleName());
            }

            try {
                return queryExecutionFactory.createQueryExecution(preparedQuery, stateMachine, slug, warningCollector);
            }
            catch (Throwable e) {
                stateMachine.transitionToFailed(e);
                throw e;
            }
        });

        return new LocalDispatchQuery(
                stateMachine,
                queryExecutionFuture,
                queryMonitor,
                clusterSizeMonitor,
                executor,
                queryManager::createQuery);
    }

@Override
    public ListenableFuture<?> execute(
            AddColumn statement,
            TransactionManager transactionManager,
            Metadata metadata,
            AccessControl accessControl,
            QueryStateMachine stateMachine,
            List<Expression> parameters,
            WarningCollector warningCollector)
    {
        Session session = stateMachine.getSession();
      	// 获取表名
        QualifiedObjectName tableName = createQualifiedObjectName(session, statement, statement.getName());
      	// 根据表名，从metadata 获取TableHandle
        // TableHandle中包括了CatalogName，ConnectorTableHandle，ConnectorTransactionHandle
        Optional<TableHandle> tableHandle = metadata.getTableHandle(session, tableName);
        if (tableHandle.isEmpty()) {
            if (!statement.isTableExists()) {
                throw semanticException(TABLE_NOT_FOUND, statement, "Table '%s' does not exist", tableName);
            }
            return immediateFuture(null);
        }

        CatalogName catalogName = metadata.getCatalogHandle(session, tableName.getCatalogName())
                .orElseThrow(() -> new TrinoException(NOT_FOUND, "Catalog does not exist: " + tableName.getCatalogName()));
				// 检测是否能够进行添加列操作
        accessControl.checkCanAddColumns(session.toSecurityContext(), tableName);

      	// 从metadata api 中获取列操作器
        Map<String, ColumnHandle> columnHandles = metadata.getColumnHandles(session, tableHandle.get());
				// 添加列操作
      	// 在trino/presto 定义添加列的标准接口(SPI)，添加列的实现是在Connector中实现
        ColumnDefinition element = statement.getColumn();
      	// 数据类型等校验
        Type type;
        try {
            type = metadata.getType(toTypeSignature(element.getType()));
        }
        catch (TypeNotFoundException e) {
            throw semanticException(TYPE_NOT_FOUND, element, "Unknown type '%s' for column '%s'", element.getType(), element.getName());
        }
        if (type.equals(UNKNOWN)) {
            throw semanticException(COLUMN_TYPE_UNKNOWN, element, "Unknown type '%s' for column '%s'", element.getType(), element.getName());
        }
        if (columnHandles.containsKey(element.getName().getValue().toLowerCase(ENGLISH))) {
            if (!statement.isColumnNotExists()) {
                throw semanticException(COLUMN_ALREADY_EXISTS, statement, "Column '%s' already exists", element.getName());
            }
            return immediateFuture(null);
        }
        if (!element.isNullable() && !metadata.getConnectorCapabilities(session, catalogName).contains(NOT_NULL_COLUMN_CONSTRAINT)) {
            throw semanticException(NOT_SUPPORTED, element, "Catalog '%s' does not support NOT NULL for column '%s'", catalogName.getCatalogName(), element.getName());
        }

        Map<String, Expression> sqlProperties = mapFromProperties(element.getProperties());
        Map<String, Object> columnProperties = metadata.getColumnPropertyManager().getProperties(
                catalogName,
                tableName.getCatalogName(),
                sqlProperties,
                session,
                metadata,
                accessControl,
                parameterExtractor(statement, parameters));
				// 封装列信息
        ColumnMetadata column = ColumnMetadata.builder()
                .setName(element.getName().getValue())
                .setType(type)
                .setNullable(element.isNullable())
                .setComment(element.getComment())
                .setProperties(columnProperties)
                .build();
				// 调用接口的addColumn方法，真正实现是在Connector中
        metadata.addColumn(session, tableHandle.get(), column);

        return immediateFuture(null);
    }