Hi Pro,
I have a question regarding calling cache()/persist() on an RDD. All RDDs in
Spark are lazily evaluated, but does calling cache()/persist() on a RDD trigger
its immediate evaluation?
My spark app is something like this:
val rdd = sc.textFile().map()
rdd.persist()
while(true){
val count = rdd.filter().count
if(count == 0)
break
newRdd = /* some codes that use `rdd` several times, and produce an new RDD
*/
rdd.unpersist()
rdd = newRdd.persist()
}
In each iteration, I persist `rdd`, and unpersist it at the end of the
iteration, replace `rdd` with persisted `newRdd`. My concern is that, if RDD is
not evaluated and persisted when persist() is called, I need to change the
position of persist()/unpersist() called to make it more efficient.
Thanks,
Pengcheng
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