GH-109: Implement Vector Validators for StringView (#886)

## What's Changed

Implement Vector Validators for StringView.

Closes #109.

Author: ViggoC

vector/src/main/java/org/apache/arrow/vector/validate/ValidateVectorBufferVisitor.java

@@ -52,14 +52,22 @@ private void validateVectorCommon(ValueVector vector) {
 
     if (vector instanceof FieldVector) {
       FieldVector fieldVector = (FieldVector) vector;
-      // TODO: https://github.com/apache/arrow/issues/41734
       int typeBufferCount = TypeLayout.getTypeBufferCount(arrowType);
-      validateOrThrow(
-          fieldVector.getFieldBuffers().size() == typeBufferCount,
-          "Expected %s buffers in vector of type %s, got %s.",
-          typeBufferCount,
-          vector.getField().getType().toString(),
-          fieldVector.getFieldBuffers().size());
+      if (TypeLayout.getTypeLayout(arrowType).isFixedBufferCount()) {
+        validateOrThrow(
+            fieldVector.getFieldBuffers().size() == typeBufferCount,
+            "Expected %s buffers in vector of type %s, got %s.",
+            typeBufferCount,
+            vector.getField().getType().toString(),
+            fieldVector.getFieldBuffers().size());
+      } else {
+        validateOrThrow(
+            fieldVector.getFieldBuffers().size() >= typeBufferCount,
+            "Expected at least %s buffers in vector of type %s, got %s.",
+            typeBufferCount,
+            vector.getField().getType().toString(),
+            fieldVector.getFieldBuffers().size());
+      }
     }
   }
 
@@ -158,7 +166,12 @@ public Void visit(BaseLargeVariableWidthVector vector, Void value) {
 
   @Override
   public Void visit(BaseVariableWidthViewVector vector, Void value) {
-    throw new UnsupportedOperationException("View vectors are not supported.");
+    final int valueCount = vector.getValueCount();
+    validateVectorCommon(vector);
+    validateOrThrow(vector.getFieldBuffers().size() >= 2, "Expected at least 2 buffers.");
+    validateValidityBuffer(vector, valueCount);
+    validateDataBuffer(vector, (long) valueCount * BaseVariableWidthViewVector.ELEMENT_SIZE);
+    return null;
   }
 
   @Override

vector/src/main/java/org/apache/arrow/vector/validate/ValidateVectorDataVisitor.java

@@ -121,7 +121,8 @@ public Void visit(BaseLargeVariableWidthVector vector, Void value) {
 
   @Override
   public Void visit(BaseVariableWidthViewVector vector, Void value) {
-    throw new UnsupportedOperationException("View vectors are not supported.");
+    vector.validateScalars();
+    return null;
   }
 
   @Override

vector/src/main/java/org/apache/arrow/vector/validate/ValidateVectorTypeVisitor.java

@@ -61,6 +61,8 @@
 import org.apache.arrow.vector.ValueVector;
 import org.apache.arrow.vector.VarBinaryVector;
 import org.apache.arrow.vector.VarCharVector;
+import org.apache.arrow.vector.ViewVarBinaryVector;
+import org.apache.arrow.vector.ViewVarCharVector;
 import org.apache.arrow.vector.compare.VectorVisitor;
 import org.apache.arrow.vector.complex.DenseUnionVector;
 import org.apache.arrow.vector.complex.FixedSizeListVector;
@@ -380,7 +382,12 @@ public Void visit(BaseLargeVariableWidthVector vector, Void value) {
 
   @Override
   public Void visit(BaseVariableWidthViewVector vector, Void value) {
-    throw new UnsupportedOperationException("View vectors are not supported.");
+    if (vector instanceof ViewVarCharVector) {
+      validateVectorCommon(vector, ArrowType.Utf8View.class);
+    } else if (vector instanceof ViewVarBinaryVector) {
+      validateVectorCommon(vector, ArrowType.BinaryView.class);
+    }
+    return null;
   }
 
   @Override

vector/src/main/java/org/apache/arrow/vector/validate/ValidateVectorVisitor.java

@@ -107,8 +107,13 @@ public Void visit(BaseLargeVariableWidthVector left, Void value) {
   }
 
   @Override
-  public Void visit(BaseVariableWidthViewVector left, Void value) {
-    throw new UnsupportedOperationException("View vectors are not supported.");
+  public Void visit(BaseVariableWidthViewVector vector, Void value) {
+    if (vector.getValueCount() > 0) {
+      if (vector.getDataBuffer() == null || vector.getDataBuffer().capacity() == 0) {
+        throw new IllegalArgumentException("valueBuffer is null or capacity is 0");
+      }
+    }
+    return null;
   }
 
   @Override

vector/src/test/java/org/apache/arrow/vector/TestVariableWidthViewVector.java

@@ -61,6 +61,7 @@
 import org.apache.arrow.vector.util.ReusableByteArray;
 import org.apache.arrow.vector.util.Text;
 import org.apache.arrow.vector.util.TransferPair;
+import org.apache.arrow.vector.validate.ValidateUtil;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -2445,7 +2446,7 @@ public void testSplitAndTransferWithLongStringsOnValiditySplit() {
         final ViewVarBinaryVector sourceVector =
             newViewVarBinaryVector(EMPTY_SCHEMA_PATH, allocator)) {
       testSplitAndTransferOnValiditySplitHelper(
-          targetVector, sourceVector, startIndex, length, data);
+          targetVector, sourceVector, startIndex, length, binaryData);
     }
   }
 
@@ -2852,4 +2853,18 @@ public void testVectorLoadUnloadOnMixedTypes() {
       }
     }
   }
+
+  @Test
+  public void testValidate() {
+    try (final ViewVarCharVector vector = new ViewVarCharVector("v", allocator)) {
+      vector.validateFull();
+      setVector(vector, STR1, STR2, STR3);
+      vector.validateFull();
+
+      vector.getDataBuffer().capacity(0);
+      ValidateUtil.ValidateException e =
+          assertThrows(ValidateUtil.ValidateException.class, () -> vector.validate());
+      assertTrue(e.getMessage().contains("Not enough capacity for data buffer"));
+    }
+  }
 }