DRILL-2940, DRILL-2847: Improve Memory Characteristics

- Update Large Buffer allocation so Drill releases immediately rather than waiting for Garbage Collection
- Remove DrillBuf.wrap() and all references to it.
- Update Parquet Reader to reduce object churn and indirection.
- Add additional metric to memory iterator
- Add Large and small buffer metric historgram tracking
- Add memory tracking reporter
- Update Netty to 4.0.27

1 files changed, 3 insertions, 1 deletions

diff --git a/exec/java-exec/src/main/java/org/apache/drill/exec/work/fragment/FragmentExecutor.java b/exec/java-exec/src/main/java/org/apache/drill/exec/work/fragment/FragmentExecutor.java
index fb2045f62..ddb828c0f 100644
--- a/exec/java-exec/src/main/java/org/apache/drill/exec/work/fragment/FragmentExecutor.java
+++ b/exec/java-exec/src/main/java/org/apache/drill/exec/work/fragment/FragmentExecutor.java
@@ -274,7 +274,9 @@ public class FragmentExecutor implements Runnable {
 
     // first close the operators and release all memory.
     try {
-      root.close();
+      if (root != null) {
+        root.close();
+      }
     } catch (final Exception e) {
       fail(e);
     }