ARROW-11788: [Java] Fix appending empty delta vectors

This PR fixes a bug where appending an empty list vector fails with a `NullPointerException`. Instead of attempting to process the delta vector, we just return early with the unmodified target vector, since there is nothing to append to the target vector from the delta vector. In addition, it fixes cases where appending an empty delta vector would've caused the same NPE, or where it'd be an optimization to not attempt processing an empty delta vector. Unit tests are added for all supported `VectorAppender` vector types. Closes apache#9581 from nbruno/ARROW-11788 Authored-by: Nick Bruno <[email protected]> Signed-off-by: liyafan82 <[email protected]>
emkornfield · Mar 1, 2021 · 137d495 · 137d495
1 parent f7cf157
commit 137d495
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diff --git a/java/vector/src/main/java/org/apache/arrow/vector/util/VectorAppender.java b/java/vector/src/main/java/org/apache/arrow/vector/util/VectorAppender.java
@@ -65,6 +65,10 @@ public ValueVector visit(BaseFixedWidthVector deltaVector, Void value) {
     Preconditions.checkArgument(targetVector.getField().getType().equals(deltaVector.getField().getType()),
             "The targetVector to append must have the same type as the targetVector being appended");
 
+    if (deltaVector.getValueCount() == 0) {
+      return targetVector; // optimization, nothing to append, return
+    }
+
     int newValueCount = targetVector.getValueCount() + deltaVector.getValueCount();
 
     // make sure there is enough capacity
@@ -90,6 +94,10 @@ public ValueVector visit(BaseVariableWidthVector deltaVector, Void value) {
     Preconditions.checkArgument(targetVector.getField().getType().equals(deltaVector.getField().getType()),
             "The targetVector to append must have the same type as the targetVector being appended");
 
+    if (deltaVector.getValueCount() == 0) {
+      return targetVector; // nothing to append, return
+    }
+
     int newValueCount = targetVector.getValueCount() + deltaVector.getValueCount();
 
     int targetDataSize = targetVector.getOffsetBuffer().getInt(
@@ -140,6 +148,10 @@ public ValueVector visit(BaseLargeVariableWidthVector deltaVector, Void value) {
     Preconditions.checkArgument(targetVector.getField().getType().equals(deltaVector.getField().getType()),
             "The targetVector to append must have the same type as the targetVector being appended");
 
+    if (deltaVector.getValueCount() == 0) {
+      return targetVector; // nothing to append, return
+    }
+
     int newValueCount = targetVector.getValueCount() + deltaVector.getValueCount();
 
     long targetDataSize = targetVector.getOffsetBuffer().getLong(
@@ -190,6 +202,10 @@ public ValueVector visit(ListVector deltaVector, Void value) {
     Preconditions.checkArgument(typeVisitor.equals(deltaVector),
           "The targetVector to append must have the same type as the targetVector being appended");
 
+    if (deltaVector.getValueCount() == 0) {
+      return targetVector; // nothing to append, return
+    }
+
     int newValueCount = targetVector.getValueCount() + deltaVector.getValueCount();
 
     int targetListSize = targetVector.getOffsetBuffer().getInt(
@@ -241,6 +257,10 @@ public ValueVector visit(LargeListVector deltaVector, Void value) {
     Preconditions.checkArgument(typeVisitor.equals(deltaVector),
             "The targetVector to append must have the same type as the targetVector being appended");
 
+    if (deltaVector.getValueCount() == 0) {
+      return targetVector; // nothing to append, return
+    }
+
     int newValueCount = targetVector.getValueCount() + deltaVector.getValueCount();
 
     long targetListSize = targetVector.getOffsetBuffer().getLong(
@@ -293,6 +313,10 @@ public ValueVector visit(FixedSizeListVector deltaVector, Void value) {
     Preconditions.checkArgument(typeVisitor.equals(deltaVector),
             "The vector to append must have the same type as the targetVector being appended");
 
+    if (deltaVector.getValueCount() == 0) {
+      return targetVector; // optimization, nothing to append, return
+    }
+
     FixedSizeListVector targetListVector = (FixedSizeListVector) targetVector;
 
     Preconditions.checkArgument(targetListVector.getListSize() == deltaVector.getListSize(),
@@ -330,6 +354,10 @@ public ValueVector visit(NonNullableStructVector deltaVector, Void value) {
     Preconditions.checkArgument(typeVisitor.equals(deltaVector),
             "The vector to append must have the same type as the targetVector being appended");
 
+    if (deltaVector.getValueCount() == 0) {
+      return targetVector; // optimization, nothing to append, return
+    }
+
     NonNullableStructVector targetStructVector = (NonNullableStructVector) targetVector;
     int newValueCount = targetVector.getValueCount() + deltaVector.getValueCount();
 
@@ -365,6 +393,10 @@ public ValueVector visit(UnionVector deltaVector, Void value) {
     Preconditions.checkArgument(targetVector.getMinorType() == deltaVector.getMinorType(),
             "The vector to append must have the same type as the targetVector being appended");
 
+    if (deltaVector.getValueCount() == 0) {
+      return targetVector; // optimization, nothing to append, return
+    }
+
     UnionVector targetUnionVector = (UnionVector) targetVector;
     int newValueCount = targetVector.getValueCount() + deltaVector.getValueCount();
 
@@ -424,6 +456,10 @@ public ValueVector visit(DenseUnionVector deltaVector, Void value) {
     Preconditions.checkArgument(targetVector.getMinorType() == deltaVector.getMinorType(),
         "The vector to append must have the same type as the targetVector being appended");
 
+    if (deltaVector.getValueCount() == 0) {
+      return targetVector; // optimization, nothing to append, return
+    }
+
     DenseUnionVector targetDenseUnionVector = (DenseUnionVector) targetVector;
     int newValueCount = targetVector.getValueCount() + deltaVector.getValueCount();