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Add java priority queue, set, deque, collection coders #5520

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@kellen kellen commented Oct 26, 2024

When using e.g. algebird PriorityQueueMonoid, scio needs to serialize java PriorityQueues. If Kryo is used, especially for small queues, there can be significant overhead.

Instead, this PR provides a PriorityQueue coder backed by a scala Ordering (as indeed the monoid is).

The coder must be created explicitly by the user so that they are asserting that the comparator of the original PriorityQueues and the reconstituted ones are the same. e.g.

implicit val pqCoder = Coders.jPriorityQueueCoder[T](ord)

@RustedBones Is there some trick I can use to get an error message when Coder[java.util.PriorityQueue[T]] fails to be derived (that's not just the generic implicitNotFound on Coder)?

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codecov bot commented Oct 26, 2024

Codecov Report

Attention: Patch coverage is 65.00000% with 7 lines in your changes missing coverage. Please review.

Project coverage is 61.44%. Comparing base (0a450e9) to head (e334184).
Report is 5 commits behind head on main.

Files with missing lines Patch % Lines
...com/spotify/scio/coders/instances/JavaCoders.scala 80.00% 3 Missing ⚠️
...ala/com/spotify/scio/testing/CoderAssertions.scala 0.00% 3 Missing ⚠️
...om/spotify/scio/coders/instances/ScalaCoders.scala 50.00% 1 Missing ⚠️
Additional details and impacted files
@@            Coverage Diff             @@
##             main    #5520      +/-   ##
==========================================
+ Coverage   61.43%   61.44%   +0.01%     
==========================================
  Files         312      312              
  Lines       11103    11118      +15     
  Branches      762      743      -19     
==========================================
+ Hits         6821     6832      +11     
- Misses       4282     4286       +4     

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I see we're also missing coders for java.util.Collection[T], java.util.Set[T] and java.util.Deque[T] which are available by default in beam

Comment on lines 83 to 84
// neither arrays nor PriorityQueues are consistentWithEquals
Coder.xmap(ScalaCoders.arrayCoder[T])(
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I think it would be better to create a coder instance, explicitly overriding consistentWithEquals instead of depending on a specific type for that reason

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I recall we've been comparing underlying coder and value ordering here, but we've not done that for scala SortedSet nor PriorityQueue.

The drawback of such check is that we must give an ordering implementation that gives a stable equal after serialization (mostly by using object ordering).

pq coderShould roundtrip() and
beOfType[Transform[_, _]] and
materializeToTransformOf[ArrayCoder[_]] and
beFullyCompliantNotConsistentWithEquals()
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shouldn't this be non deterministic too ?

Comment on lines 161 to 162
// custom ordering must have stable equal after serialization
implicit val pqOrd: Ordering[String] = FlippedStringOrdering
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@RustedBones RustedBones Nov 4, 2024

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Not really happy about this

@RustedBones RustedBones changed the title Add java priority queue coder Add java priority queue, set, deque, collection coders Nov 4, 2024
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2 participants