rebase on Add ExtensionTypeWriterFactory to TransferPair

Author: tmater

vector/src/main/java/org/apache/arrow/vector/complex/impl/VariantWriterFactory.java

@@ -18,6 +18,9 @@
 
 import org.apache.arrow.memory.BufferAllocator;
 import org.apache.arrow.vector.FieldVector;
+import org.apache.arrow.vector.ValueVector;
+import org.apache.arrow.vector.complex.impl.VariantWriterImpl;
+import org.apache.arrow.vector.complex.writer.FieldWriter;
 import org.apache.arrow.vector.types.pojo.ArrowType;
 import org.apache.arrow.vector.types.pojo.ArrowType.ExtensionType;
 import org.apache.arrow.vector.types.pojo.ExtensionTypeRegistry;
@@ -77,4 +80,9 @@ public boolean isComplex() {
     // and value)
     return false;
   }
+
+  @Override
+  public FieldWriter getNewFieldWriter(ValueVector vector) {
+    return new VariantWriterImpl((VariantVector) vector);
+  }
 }

vector/src/main/java/org/apache/arrow/vector/extension/VariantType.java

@@ -17,6 +17,8 @@
 package org.apache.arrow.vector.holders;
 
 import org.apache.arrow.memory.ArrowBuf;
+import org.apache.arrow.vector.extension.VariantType;
+import org.apache.arrow.vector.types.pojo.ArrowType;
 
 @SuppressWarnings("checkstyle:VisibilityModifier")
 public final class NullableVariantHolder extends ExtensionHolder {
@@ -45,4 +47,9 @@ public int hashCode() {
   public String toString() {
     throw new UnsupportedOperationException();
   }
+
+  @Override
+  public ArrowType type() {
+    return VariantType.INSTANCE;
+  }
 }

vector/src/main/java/org/apache/arrow/vector/holders/NullableVariantHolder.java

@@ -17,6 +17,8 @@
 package org.apache.arrow.vector.holders;
 
 import org.apache.arrow.memory.ArrowBuf;
+import org.apache.arrow.vector.extension.VariantType;
+import org.apache.arrow.vector.types.pojo.ArrowType;
 
 @SuppressWarnings("checkstyle:VisibilityModifier")
 public final class VariantHolder extends ExtensionHolder {
@@ -45,4 +47,9 @@ public int hashCode() {
   public String toString() {
     throw new UnsupportedOperationException();
   }
+
+  @Override
+  public ArrowType type() {
+    return VariantType.INSTANCE;
+  }
 }

vector/src/main/java/org/apache/arrow/vector/holders/VariantHolder.java

@@ -28,13 +28,13 @@
 import org.apache.arrow.memory.BufferAllocator;
 import org.apache.arrow.memory.RootAllocator;
 import org.apache.arrow.vector.complex.impl.VariantReaderImpl;
-import org.apache.arrow.vector.complex.impl.VariantWriterFactory;
 import org.apache.arrow.vector.complex.impl.VariantWriterImpl;
-import org.apache.arrow.vector.complex.writer.FieldWriter;
+import org.apache.arrow.vector.extension.VariantType;
 import org.apache.arrow.vector.extension.VariantVector;
 import org.apache.arrow.vector.holders.ExtensionHolder;
 import org.apache.arrow.vector.holders.NullableVariantHolder;
 import org.apache.arrow.vector.holders.VariantHolder;
+import org.apache.arrow.vector.types.pojo.ArrowType;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -305,7 +305,13 @@ void testWriteWithUnsupportedHolder() {
     try (VariantVector vector = new VariantVector("test", allocator);
         VariantWriterImpl writer = new VariantWriterImpl(vector)) {
 
-      ExtensionHolder unsupportedHolder = new ExtensionHolder() {};
+      ExtensionHolder unsupportedHolder =
+          new ExtensionHolder() {
+            @Override
+            public ArrowType type() {
+              return VariantType.INSTANCE;
+            }
+          };
 
       writer.setPosition(0);
 
@@ -440,30 +446,6 @@ void testReaderReadWithNonNullableVariantHolder() {
     }
   }
 
-  // ========== Factory Tests ==========
-
-  @Test
-  void testVariantWriterFactory() {
-    VariantWriterFactory factory = new VariantWriterFactory();
-
-    try (VariantVector vector = new VariantVector("test", allocator)) {
-      FieldWriter writer = factory.getWriterImpl(vector);
-      assertNotNull(writer);
-      assertTrue(writer instanceof VariantWriterImpl);
-    }
-  }
-
-  @Test
-  void testVariantWriterFactoryWithNonVariantVector() {
-    VariantWriterFactory factory = new VariantWriterFactory();
-
-    // Use UuidVector as a different extension type
-    try (UuidVector uuidVector = new UuidVector("uuid", allocator)) {
-      FieldWriter writer = factory.getWriterImpl(uuidVector);
-      assertNull(writer);
-    }
-  }
-
   // ========== Transfer Pair Tests ==========
 
   @Test