GitHub user aljoscha opened a pull request: https://github.com/apache/flink/pull/1802
[FLINK-3174] Add MergingWindowAssigner and SessionWindows This introduces MergingWindowAssigner, an extension of WindowAssigner that can merge windows. When using a MergingWindowAssigner the WindowOperator eagerly merges windows when processing elements. For keeping track of in-flight windows and for merging windows this adds MergingWindowSet, this keeps track of windows per key. Only when using a WindowAssigners is the more costly merging logic used in the WindowOperator. For triggers there is new method Trigger.onMerge() that notifies the trigger of the new merged window. This allows the trigger to set a timer for the newly merged window. This also adds AbstractStateBackend.mergePartitionedStates for merging state of several source namespaces into a target namespace. This is only possible for the newly introduced MergingState which is an extension of AppendingState. Only ReducingState and ListState are MergingState while FoldingState is now an AppendingState. This enables proper support for session windows. This also adds the SessionWindows window assigner and adapts an existing session example and adds test cases. You can merge this pull request into a Git repository by running: $ git pull https://github.com/aljoscha/flink window-sessions-eager Alternatively you can review and apply these changes as the patch at: https://github.com/apache/flink/pull/1802.patch To close this pull request, make a commit to your master/trunk branch with (at least) the following in the commit message: This closes #1802 ---- commit bda4e019cc464f411a2b62eaeab41a87f3961a21 Author: Aljoscha Krettek <aljoscha.kret...@gmail.com> Date: 2015-12-15T16:37:48Z [FLINK-3174] Add MergingWindowAssigner and SessionWindows This introduces MergingWindowAssigner, an extension of WindowAssigner that can merge windows. When using a MergingWindowAssigner the WindowOperator eagerly merges windows when processing elements. For keeping track of in-flight windows and for merging windows this adds MergingWindowSet, this keeps track of windows per key. Only when using a WindowAssigners is the more costly merging logic used in the WindowOperator. For triggers there is new method Trigger.onMerge() that notifies the trigger of the new merged window. This allows the trigger to set a timer for the newly merged window. This also adds AbstractStateBackend.mergePartitionedStates for merging state of several source namespaces into a target namespace. This is only possible for the newly introduced MergingState which is an extension of AppendingState. Only ReducingState and ListState are MergingState while FoldingState is now an AppendingState. This enables proper support for session windows. This also adds the SessionWindows window assigner and adapts an existing session example and adds test cases. ---- --- If your project is set up for it, you can reply to this email and have your reply appear on GitHub as well. If your project does not have this feature enabled and wishes so, or if the feature is enabled but not working, please contact infrastructure at infrastruct...@apache.org or file a JIRA ticket with INFRA. ---