ORC-422 - Fix issue with Predicate push down when lower/upper bounds are set

[moresandeep]

This PR fixes a bug where Predicate push down will not return proper values when upper and lower bounds are set for StringStatisticsImpl.
This patch also contains removing some unused imports as part of cleanup.

[moresandeep]

Hello @omalley I am updating a work in progress patch for you to look at. I have a bunch of lines commented in there which I'll take out in the final patch and cleanup the code, apologies for the rough code, I don't want to delay this patch further.

Basically, the crux of the patch is in file RecordReaderImpl line # 325 and # 335, what I am doing here is depending on whether upperbound or lowerbound is set for corner cases where the predicate literal equals upperbound or lowerbound I am picking the appropriate value.
e.g.

/* since min value is truncated when we have compare=0, it means the predicate string is BEFORE the min value*/
    else if (minCompare == 0 && isLowerBoundSet) {
      return Location.BEFORE;
    }

and

/* if upperbound is set then location here will be AFTER */
 else if (maxCompare == 0 && isUpperBoundSet) {
   return Location.AFTER;
 }

I also, tried to write up UnitTests to test all the corner case scenarios that I could think. I could not find a way test greater than since there is no Operator 'GREATER_THAN', code suggest using 'NOT' Operator, is there an example that I can look at for something like NOT LESS_THAN.

[moresandeep]

Hello @omalley can you take a look at the new changes which addresses the fixes.

[omalley]

I just committed this. Thanks, Sandeep!