聊聊flink Table的Time Attributes

DataStream<Tuple2<String, String>> stream = ...;
​
// declare an additional logical field as a processing time attribute
Table table = tEnv.fromDataStream(stream, "Username, Data, UserActionTime.proctime");
​
WindowedTable windowedTable = table.window(Tumble.over("10.minutes").on("UserActionTime").as("userActionWindow"));

// define a table source with a processing attribute
public class UserActionSource implements StreamTableSource<Row>, DefinedProctimeAttribute {
​
    @Override
    public TypeInformation<Row> getReturnType() {
        String[] names = new String[] {"Username" , "Data"};
        TypeInformation[] types = new TypeInformation[] {Types.STRING(), Types.STRING()};
        return Types.ROW(names, types);
    }
​
    @Override
    public DataStream<Row> getDataStream(StreamExecutionEnvironment execEnv) {
        // create stream
        DataStream<Row> stream = ...;
        return stream;
    }
​
    @Override
    public String getProctimeAttribute() {
        // field with this name will be appended as a third field
        return "UserActionTime";
    }
}
​
// register table source
tEnv.registerTableSource("UserActions", new UserActionSource());
​
WindowedTable windowedTable = tEnv
    .scan("UserActions")
    .window(Tumble.over("10.minutes").on("UserActionTime").as("userActionWindow"));

// Option 1:
​
// extract timestamp and assign watermarks based on knowledge of the stream
DataStream<Tuple2<String, String>> stream = inputStream.assignTimestampsAndWatermarks(...);
​
// declare an additional logical field as an event time attribute
Table table = tEnv.fromDataStream(stream, "Username, Data, UserActionTime.rowtime");
​
​
// Option 2:
​
// extract timestamp from first field, and assign watermarks based on knowledge of the stream
DataStream<Tuple3<Long, String, String>> stream = inputStream.assignTimestampsAndWatermarks(...);
​
// the first field has been used for timestamp extraction, and is no longer necessary
// replace first field with a logical event time attribute
Table table = tEnv.fromDataStream(stream, "UserActionTime.rowtime, Username, Data");
​
// Usage:
​
WindowedTable windowedTable = table.window(Tumble.over("10.minutes").on("UserActionTime").as("userActionWindow"));

// define a table source with a rowtime attribute
public class UserActionSource implements StreamTableSource<Row>, DefinedRowtimeAttributes {
​
    @Override
    public TypeInformation<Row> getReturnType() {
        String[] names = new String[] {"Username", "Data", "UserActionTime"};
        TypeInformation[] types =
            new TypeInformation[] {Types.STRING(), Types.STRING(), Types.LONG()};
        return Types.ROW(names, types);
    }
​
    @Override
    public DataStream<Row> getDataStream(StreamExecutionEnvironment execEnv) {
        // create stream
        // ...
        // assign watermarks based on the "UserActionTime" attribute
        DataStream<Row> stream = inputStream.assignTimestampsAndWatermarks(...);
        return stream;
    }
​
    @Override
    public List<RowtimeAttributeDescriptor> getRowtimeAttributeDescriptors() {
        // Mark the "UserActionTime" attribute as event-time attribute.
        // We create one attribute descriptor of "UserActionTime".
        RowtimeAttributeDescriptor rowtimeAttrDescr = new RowtimeAttributeDescriptor(
            "UserActionTime",
            new ExistingField("UserActionTime"),
            new AscendingTimestamps());
        List<RowtimeAttributeDescriptor> listRowtimeAttrDescr = Collections.singletonList(rowtimeAttrDescr);
        return listRowtimeAttrDescr;
    }
}
​
// register the table source
tEnv.registerTableSource("UserActions", new UserActionSource());
​
WindowedTable windowedTable = tEnv
    .scan("UserActions")
    .window(Tumble.over("10.minutes").on("UserActionTime").as("userActionWindow"));

/**
  * Extends a [[TableSource]] to specify a processing time attribute.
  */
trait DefinedProctimeAttribute {
​
  /**
    * Returns the name of a processing time attribute or null if no processing time attribute is
    * present.
    *
    * The referenced attribute must be present in the [[TableSchema]] of the [[TableSource]] and of
    * type [[Types.SQL_TIMESTAMP]].
    */
  @Nullable
  def getProctimeAttribute: String
}
​
/**
  * Extends a [[TableSource]] to specify rowtime attributes via a
  * [[RowtimeAttributeDescriptor]].
  */
trait DefinedRowtimeAttributes {
​
  /**
    * Returns a list of [[RowtimeAttributeDescriptor]] for all rowtime attributes of the table.
    *
    * All referenced attributes must be present in the [[TableSchema]] of the [[TableSource]] and of
    * type [[Types.SQL_TIMESTAMP]].
    *
    * @return A list of [[RowtimeAttributeDescriptor]].
    */
  def getRowtimeAttributeDescriptors: util.List[RowtimeAttributeDescriptor]
}
​
/**
  * Describes a rowtime attribute of a [[TableSource]].
  *
  * @param attributeName The name of the rowtime attribute.
  * @param timestampExtractor The timestamp extractor to derive the values of the attribute.
  * @param watermarkStrategy The watermark strategy associated with the attribute.
  */
class RowtimeAttributeDescriptor(
  val attributeName: String,
  val timestampExtractor: TimestampExtractor,
  val watermarkStrategy: WatermarkStrategy) {
​
  /** Returns the name of the rowtime attribute. */
  def getAttributeName: String = attributeName
​
  /** Returns the [[TimestampExtractor]] for the attribute. */
  def getTimestampExtractor: TimestampExtractor = timestampExtractor
​
  /** Returns the [[WatermarkStrategy]] for the attribute. */
  def getWatermarkStrategy: WatermarkStrategy = watermarkStrategy
​
  override def equals(other: Any): Boolean = other match {
    case that: RowtimeAttributeDescriptor =>
        Objects.equals(attributeName, that.attributeName) &&
        Objects.equals(timestampExtractor, that.timestampExtractor) &&
        Objects.equals(watermarkStrategy, that.watermarkStrategy)
    case _ => false
  }
​
  override def hashCode(): Int = {
    Objects.hash(attributeName, timestampExtractor, watermarkStrategy)
  }
}