FlatMapGroupsWithState Unary Logical Operator¶

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

• KeyValueGroupedDataset.mapGroupsWithState

• KeyValueGroupedDataset.flatMapGroupsWithState

Execution Planning¶

FlatMapGroupsWithState is resolved (planned) to:

• FlatMapGroupsWithStateExec unary physical operator for streaming datasets (in FlatMapGroupsWithStateStrategy execution planning strategy)

• MapGroupsExec physical operator for batch datasets (in BasicOperators execution planning strategy)

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.