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FlatMapGroupsWithState Unary Logical Operator

FlatMapGroupsWithState is a unary logical operator that represents the following operators in a logical query plan of a streaming query:


A unary logical operator (UnaryNode) is a logical operator with a single <> logical operator.

Read up on UnaryNode (and logical operators in general) in The Internals of Spark SQL online book.

Execution Planning

FlatMapGroupsWithState is resolved (planned) to:

Creating Instance

FlatMapGroupsWithState takes the following to be created:

  • State function ((Any, Iterator[Any], LogicalGroupState[Any]) => Iterator[Any])
  • Catalyst Expression for keys
  • Catalyst Expression for values
  • Grouping Attributes
  • Data Attributes
  • Output Object Attribute
  • State ExpressionEncoder
  • OutputMode
  • isMapGroupsWithState flag (default: false)
  • GroupStateTimeout
  • Child logical operator

FlatMapGroupsWithState is created (using apply factory method) for KeyValueGroupedDataset.mapGroupsWithState and KeyValueGroupedDataset.flatMapGroupsWithState operators.

Creating SerializeFromObject with FlatMapGroupsWithState

apply[K: Encoder, V: Encoder, S: Encoder, U: Encoder](
  func: (Any, Iterator[Any], LogicalGroupState[Any]) => Iterator[Any],
  groupingAttributes: Seq[Attribute],
  dataAttributes: Seq[Attribute],
  outputMode: OutputMode,
  isMapGroupsWithState: Boolean,
  timeout: GroupStateTimeout,
  child: LogicalPlan): LogicalPlan

apply creates a SerializeFromObject logical operator with a FlatMapGroupsWithState as its child logical operator.

Internally, apply creates SerializeFromObject object consumer (aka unary logical operator) with FlatMapGroupsWithState logical plan.

Internally, apply finds ExpressionEncoder for the type S and creates a FlatMapGroupsWithState with UnresolvedDeserializer for the types K and V.

In the end, apply creates a SerializeFromObject object consumer with the FlatMapGroupsWithState.

apply is used for KeyValueGroupedDataset.mapGroupsWithState and KeyValueGroupedDataset.flatMapGroupsWithState operators.

Last update: 2020-11-01