FLINK基础（138）：DS流与表转换(4) Handling of (Insert-Only) Streams（3）createTemporaryView(FLINK1.13以上)

NO.1 code

A DataStream can be registered directly as a view (possibly enriched with a schema).

Views created from a DataStream can only be registered as temporary views. Due to their inline/anonymous nature, it is not possible to register them in a permanent catalog.

The following code shows how to use createTemporaryView for different scenarios.

import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.streaming.api.datastream.DataStream;

// create some DataStream
DataStream<Tuple2<Long, String>> dataStream = env.fromElements(
    Tuple2.of(12L, "Alice"),
    Tuple2.of(0L, "Bob"));


// === EXAMPLE 1 ===

// register the DataStream as view "MyView" in the current session
// all columns are derived automatically

tableEnv.createTemporaryView("MyView", dataStream);

tableEnv.from("MyView").printSchema();

// prints:
// (
//  `f0` BIGINT NOT NULL,
//  `f1` STRING
// )


// === EXAMPLE 2 ===

// register the DataStream as view "MyView" in the current session,
// provide a schema to adjust the columns similar to `fromDataStream`

// in this example, the derived NOT NULL information has been removed

tableEnv.createTemporaryView(
    "MyView",
    dataStream,
    Schema.newBuilder()
        .column("f0", "BIGINT")
        .column("f1", "STRING")
        .build());

tableEnv.from("MyView").printSchema();

// prints:
// (
//  `f0` BIGINT,
//  `f1` STRING
// )


// === EXAMPLE 3 ===

// use the Table API before creating the view if it is only about renaming columns

tableEnv.createTemporaryView(
    "MyView",
    tableEnv.fromDataStream(dataStream).as("id", "name"));

tableEnv.from("MyView").printSchema();

// prints:
// (
//  `id` BIGINT NOT NULL,
//  `name` STRING
// )