Siyuan Hua commented on APEXMALHAR-2244:

Each spillable DS implementation use a SpillableStateStore to store things and 
we can make ManagedTimeUnifiedStateImpl implement the store as well and it can 
take some time extract function to get/calculate time and time buckets from 
each V/KV data.  And the Store can be setup by the WindowedOperator, correct? 

> Optimize WindowedStorage and Spillable data structures for time series
> ----------------------------------------------------------------------
>                 Key: APEXMALHAR-2244
>                 URL: https://issues.apache.org/jira/browse/APEXMALHAR-2244
>             Project: Apache Apex Malhar
>          Issue Type: Sub-task
>            Reporter: David Yan
>            Assignee: Siyuan Hua
> The spillable data structures currently does not make any assumption about 
> the key that is used in Managed State, and as a result, it uses 
> ManagedStateImpl to interface with Managed State and uses time buckets that 
> are based on the apex window id. But for WindowedStorage used by 
> WindowedOperator, the key to the storage is a window, which is event time 
> based. Using the default ManagedStateImpl would be very inefficient for event 
> time based keys, since it would write data that would belong to the same 
> window to different time buckets.
> On a high level, the below summarizes roughly what needs to be done:
> 1. a way to tell the spillable data structures to use the 
> ManagedTimeUnifiedStateImpl
> 2. a way to tell the spillable data structures how to extract the timestamp 
> from the key. Note that in the case of WindowedOperator, the timestamp should 
> be the end timestamp of the window (beginTimeMillis + durationMillis), not 
> the begin timestamp.
> 3. a way to tell the spillable data structures how to assign the time bucket 
> given that timestamp
> 4. with point 3, the spillable implementations of WindowedStorage will need 
> to take a config parameter that says how much time (in millis) is each time 
> bucket
> 5. only purge a time bucket when all keys that belong to that time bucket are 
> removed and the apex window id of the first window in which the keys are all 
> removed has been committed

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