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Collections API - #1606
Collections API#1606
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| K: AvroRecordCodec: Boundable: JsonFormat: ClassTag, | ||
| V: AvroRecordCodec: ClassTag, | ||
| M: JsonFormat: GetComponent[?, Bounds[K]] | ||
| ](id: ID, rasterQuery: LayerQuery[K, M], numPartitions: Int, indexFilterOnly: Boolean): Seq[(K, V)] with Metadata[M] |
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this read should not have numPartitions argument. All the reads should be using threads to distributed the work as much as makes sense, but by definition you only ever get one partition, the collection.
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It looks like a lot of code is shared between the collection readers and rdd readers in S3, File, Hadoop, and Cassandra. HBase and Accumulo are exceptions because they have Reading a collection seems exactly like reading a partition. Maybe we can abstract all of that code into something that reads just the ranges and the splitting/filtering of those ranges can be up to the whichever reader. I'm mostly concerned because this async code is very fiddly and error-prone. I can see us having to refactor it again when we learn something new. |
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| nondeterminism.njoin(maxOpen = threads, maxQueued = threads) { range map read }.runFoldMap(identity).unsafePerformSync |
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readers need to be closed, I'm unsure on what consequence, but probably nothing good.
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are not they closing with cache expiration?
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I can see how that would mess with the caching though, if you had multiple async calls n to a Collection reader. If that's the case it almost makes it seem like CollectionsReader needs to be closable, as it will invariably represent some resources.
Main use case for these is to be called from endpoints to work on "small" areas, so async read calls are totally in scope of design.
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Same story goes for HBase and Accumulo collection reads, they're based on some version of range/batch writers.
…by already runing jobs on a runing cluster
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| object CollectionLayerReader { | ||
| def njoin[K: AvroRecordCodec: Boundable, V: AvroRecordCodec]( |
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We ask for AvroRecordCodec but we do not use them. If the readFunc is Long => Option[Array[Byte]] we can spin the iterator here and do the decoding. You'll need an extra refinementFilter: K => Boolean to capture the filterIndexOnly param.
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This is the list of places where it looks like we should use
They can not be used in:
.. because one or another those backends read ranges rather than (K,V). I think that's fine, we don't need to abstract over that. |
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Cannot be used in HadoopRDDReader as we use MR job |
…n/geotrellis into feature/collections-api # Conflicts: # accumulo/src/main/scala/geotrellis/spark/io/accumulo/AccumuloCollectionReader.scala
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+1, submitted a meta-PR that tidies up the njoin signature a little. |
Feature/collections api njoin
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#1605
Backends support: