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From JamesRTaylor <>
Subject [GitHub] phoenix issue #239: Phoenix-3744: Support snapshot scanners for MR-based que...
Date Mon, 08 May 2017 21:12:15 GMT
Github user JamesRTaylor commented on the issue:
    I don't think it's necessary to fully understand the functionality to do the refactoring
I've mentioned, @akshita-malhotra. Here's how I'd recommend approaching it:
    * create a new interface solely for the purpose of only abstracting RegionCoprocessorEnvironment
access called RegionContext. The interface would have at least two methods: getRegion and
getConfiguration. We might need more if other methods are called in RegionCoprocessorEnvironment.
    * have two implementations of this interface: RegionCoprocessorContext and RegionShapshotContext.
The constructor of RegionCoprocessorContext would take a RegionCoprocessorEnvironment as an
argument, while the RegionShapshotContext would take a Region and Configuration.
    * do an across the board replace of RegionCoprocessorEnvironment with RegionContext. You
can likely not do this for secondary index related code (org.apache.phoenix.hbase.index.Indexer
and PhoenixTransactionalIndexer). You'll find out here if other methods are called from RegionCoprocessorEnvironment
or ObserverContext (which can be dealt with in a variety of ways, for example by throwing
an UnsupportedOperationException if need be in the snapshot implementation).
    * in the top level coprocessor methods that pass in RegionCoprocessorEnvironment (mostly
abstract BaseScannerRegionObserver class), instantiate a RegionCoprocessorContext by passing
in the RegionCoprocessorEnvironment. From this point onward, all access will go through the
RegionContext interface.
    You could do this refactoring completely separate from the PHOENIX-3744 so that you don't
mix the two. Then PHOENIX-3744 would have something like a RegionScannerFactory (your RegionObserverUtil)
that gives you back a RegionScanner given a RegionContext and you'd create a RegionShapshotContext
as the backing implementation in your snapshot reading code.

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