[FLINK-2683] Add utilities for heap-backed keyed state in time panes

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Implemented
• Affects Version/s: 0.10.0
• Fix Version/s: 0.10.0
• Component/s: API / DataStream
• Assignee: Stephan Ewen
• Reporter: Stephan Ewen
• Created: 15/Sep/15 12:30
• Updated: 28/Feb/19 11:15
• Resolved: 23/Sep/15 18:31

Description

Time panes are commonly used for aligned time windows (tumbling and sliding). These utilities would represent the panes with per-pane keyed state.

The implementation must support:

• Evicting panes efficiently
• iterating over the union of all panes' state per key for all keys (computing the window function for all keys)
• efficient append the state for a key in a random pane