Description
I found getDetachedValue() appears quite often when jstack on one of my pipeline. A piece of stacktrace is shown below. In the pipeline, most of types we used are immutable (e.g. java primitives, strings, protobuf). I think we can avoid deep-copy overhead here.
"main" prio=10 tid=0x00007f0de801d800 nid=0x7ef runnable [0x00007f0dee66c000]
java.lang.Thread.State: RUNNABLE
at org.apache.hadoop.io.BytesWritable.<init>(BytesWritable.java:52)
at org.apache.hadoop.io.BytesWritable.<init>(BytesWritable.java:46)
at sun.reflect.GeneratedConstructorAccessor9.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at java.lang.Class.newInstance0(Class.java:355)
at java.lang.Class.newInstance(Class.java:308)
at org.apache.crunch.types.writable.WritableDeepCopier.deepCopy(WritableDeepCopier.java:63)
at org.apache.crunch.types.writable.WritableDeepCopier.deepCopy(WritableDeepCopier.java:36)
at org.apache.crunch.types.writable.WritableType.getDetachedValue(WritableType.java:125)
at org.apache.crunch.impl.mr.emit.IntermediateEmitter.emit(IntermediateEmitter.java:54)