GH-38414 [Java] [Vector] Add Delta dictionary support.

Add a delta encoding flag to the DictionaryEncoding class.
Add a BaseDictionary interface (poor name but provides backwards compatibility) that
Dictionary implements it and a new BatchedDictionary class that handles writing data
to a dictionary and index allowing for flushing in a writer writeBatch call and either
replacing or delta encoding the dictionary.

Fix for #38414

java/c/src/main/java/org/apache/arrow/c/ArrayExporter.java

@@ -29,7 +29,7 @@
 import org.apache.arrow.memory.ArrowBuf;
 import org.apache.arrow.memory.BufferAllocator;
 import org.apache.arrow.vector.FieldVector;
-import org.apache.arrow.vector.dictionary.Dictionary;
+import org.apache.arrow.vector.dictionary.BaseDictionary;
 import org.apache.arrow.vector.dictionary.DictionaryProvider;
 import org.apache.arrow.vector.types.pojo.DictionaryEncoding;
 
@@ -110,7 +110,7 @@ void export(ArrowArray array, FieldVector vector, DictionaryProvider dictionaryP
       }
 
       if (dictionaryEncoding != null) {
-        Dictionary dictionary = dictionaryProvider.lookup(dictionaryEncoding.getId());
+        BaseDictionary dictionary = dictionaryProvider.lookup(dictionaryEncoding.getId());
         checkNotNull(dictionary, "Dictionary lookup failed on export of dictionary encoded array");
 
         data.dictionary = ArrowArray.allocateNew(allocator);

java/c/src/main/java/org/apache/arrow/c/ArrayImporter.java

@@ -29,7 +29,7 @@
 import org.apache.arrow.memory.BufferAllocator;
 import org.apache.arrow.util.Preconditions;
 import org.apache.arrow.vector.FieldVector;
-import org.apache.arrow.vector.dictionary.Dictionary;
+import org.apache.arrow.vector.dictionary.BaseDictionary;
 import org.apache.arrow.vector.dictionary.DictionaryProvider;
 import org.apache.arrow.vector.ipc.message.ArrowFieldNode;
 import org.apache.arrow.vector.types.pojo.DictionaryEncoding;
@@ -103,7 +103,7 @@ private void doImport(ArrowArray.Snapshot snapshot) {
       DictionaryEncoding encoding = vector.getField().getDictionary();
       checkNotNull(encoding, "Missing encoding on import of ArrowArray with dictionary");
 
-      Dictionary dictionary = dictionaryProvider.lookup(encoding.getId());
+      BaseDictionary dictionary = dictionaryProvider.lookup(encoding.getId());
       checkNotNull(dictionary, "Dictionary lookup failed on import of ArrowArray with dictionary");
 
       // reset the dictionary vector to the initial state

java/c/src/main/java/org/apache/arrow/c/ArrowArrayStreamReader.java

@@ -26,7 +26,7 @@
 import java.util.stream.Collectors;
 
 import org.apache.arrow.memory.BufferAllocator;
-import org.apache.arrow.vector.dictionary.Dictionary;
+import org.apache.arrow.vector.dictionary.BaseDictionary;
 import org.apache.arrow.vector.ipc.ArrowReader;
 import org.apache.arrow.vector.types.pojo.Schema;
 
@@ -52,12 +52,12 @@ final class ArrowArrayStreamReader extends ArrowReader {
   }
 
   @Override
-  public Map<Long, Dictionary> getDictionaryVectors() {
+  public Map<Long, BaseDictionary> getDictionaryVectors() {
     return provider.getDictionaryIds().stream().collect(Collectors.toMap(Function.identity(), provider::lookup));
   }
 
   @Override
-  public Dictionary lookup(long id) {
+  public BaseDictionary lookup(long id) {
     return provider.lookup(id);
   }
 

java/c/src/main/java/org/apache/arrow/c/CDataDictionaryProvider.java

@@ -21,7 +21,8 @@
 import java.util.Map;
 import java.util.Set;
 
-import org.apache.arrow.vector.dictionary.Dictionary;
+import org.apache.arrow.vector.dictionary.BaseDictionary;
+import org.apache.arrow.vector.dictionary.BatchedDictionary;
 import org.apache.arrow.vector.dictionary.DictionaryProvider;
 
 /**
@@ -39,14 +40,14 @@
  */
 public class CDataDictionaryProvider implements DictionaryProvider, AutoCloseable {
 
-  private final Map<Long, Dictionary> map;
+  private final Map<Long, BaseDictionary> map;
 
   public CDataDictionaryProvider() {
     this.map = new HashMap<>();
   }
 
-  void put(Dictionary dictionary) {
-    Dictionary previous = map.put(dictionary.getEncoding().getId(), dictionary);
+  void put(BaseDictionary dictionary) {
+    BaseDictionary previous = map.put(dictionary.getEncoding().getId(), dictionary);
     if (previous != null) {
       previous.getVector().close();
     }
@@ -58,16 +59,25 @@ public final Set<Long> getDictionaryIds() {
   }
 
   @Override
-  public Dictionary lookup(long id) {
+  public BaseDictionary lookup(long id) {
     return map.get(id);
   }
 
   @Override
   public void close() {
-    for (Dictionary dictionary : map.values()) {
+    for (BaseDictionary dictionary : map.values()) {
       dictionary.getVector().close();
     }
     map.clear();
   }
 
+  @Override
+  public void resetBatchedDictionaries() {
+    map.values().forEach( dictionary -> {
+      if (dictionary instanceof BatchedDictionary) {
+        ((BatchedDictionary) dictionary).reset();
+      }
+    });
+  }
+
 }

java/c/src/main/java/org/apache/arrow/c/SchemaExporter.java

@@ -28,7 +28,7 @@
 import org.apache.arrow.c.jni.PrivateData;
 import org.apache.arrow.memory.ArrowBuf;
 import org.apache.arrow.memory.BufferAllocator;
-import org.apache.arrow.vector.dictionary.Dictionary;
+import org.apache.arrow.vector.dictionary.BaseDictionary;
 import org.apache.arrow.vector.dictionary.DictionaryProvider;
 import org.apache.arrow.vector.types.pojo.DictionaryEncoding;
 import org.apache.arrow.vector.types.pojo.Field;
@@ -95,7 +95,7 @@ void export(ArrowSchema schema, Field field, DictionaryProvider dictionaryProvid
       }
 
       if (dictionaryEncoding != null) {
-        Dictionary dictionary = dictionaryProvider.lookup(dictionaryEncoding.getId());
+        BaseDictionary dictionary = dictionaryProvider.lookup(dictionaryEncoding.getId());
         checkNotNull(dictionary, "Dictionary lookup failed on export of field with dictionary");
 
         data.dictionary = ArrowSchema.allocateNew(allocator);

java/c/src/test/java/org/apache/arrow/c/StreamTest.java

@@ -42,6 +42,7 @@
 import org.apache.arrow.vector.VectorUnloader;
 import org.apache.arrow.vector.compare.Range;
 import org.apache.arrow.vector.compare.RangeEqualsVisitor;
+import org.apache.arrow.vector.dictionary.BaseDictionary;
 import org.apache.arrow.vector.dictionary.Dictionary;
 import org.apache.arrow.vector.dictionary.DictionaryProvider;
 import org.apache.arrow.vector.ipc.ArrowReader;
@@ -244,7 +245,7 @@ void roundtrip(Schema schema, List<ArrowRecordBatch> batches, DictionaryProvider
         }
         assertThat(reader.loadNextBatch()).isFalse();
         assertThat(reader.getDictionaryIds()).isEqualTo(provider.getDictionaryIds());
-        for (Map.Entry<Long, Dictionary> entry : reader.getDictionaryVectors().entrySet()) {
+        for (Map.Entry<Long, BaseDictionary> entry : reader.getDictionaryVectors().entrySet()) {
           final FieldVector expected = provider.lookup(entry.getKey()).getVector();
           final FieldVector actual = entry.getValue().getVector();
           assertVectorsEqual(expected, actual);
@@ -286,7 +287,7 @@ static class InMemoryArrowReader extends ArrowReader {
     }
 
     @Override
-    public Dictionary lookup(long id) {
+    public BaseDictionary lookup(long id) {
       return provider.lookup(id);
     }
 
@@ -296,7 +297,7 @@ public Set<Long> getDictionaryIds() {
     }
 
     @Override
-    public Map<Long, Dictionary> getDictionaryVectors() {
+    public Map<Long, BaseDictionary> getDictionaryVectors() {
       return getDictionaryIds().stream().collect(Collectors.toMap(Function.identity(), this::lookup));
     }
 

java/flight/flight-core/src/main/java/org/apache/arrow/flight/DictionaryUtils.java

@@ -30,7 +30,7 @@
 import org.apache.arrow.vector.FieldVector;
 import org.apache.arrow.vector.VectorSchemaRoot;
 import org.apache.arrow.vector.VectorUnloader;
-import org.apache.arrow.vector.dictionary.Dictionary;
+import org.apache.arrow.vector.dictionary.BaseDictionary;
 import org.apache.arrow.vector.dictionary.DictionaryProvider;
 import org.apache.arrow.vector.ipc.message.ArrowDictionaryBatch;
 import org.apache.arrow.vector.ipc.message.IpcOption;
@@ -66,7 +66,7 @@ static Schema generateSchemaMessages(final Schema originalSchema, final FlightDe
     }
     // Create and write dictionary batches
     for (Long id : dictionaryIds) {
-      final Dictionary dictionary = provider.lookup(id);
+      final BaseDictionary dictionary = provider.lookup(id);
       final FieldVector vector = dictionary.getVector();
       final int count = vector.getValueCount();
       // Do NOT close this root, as it does not actually own the vector.

java/flight/flight-core/src/main/java/org/apache/arrow/flight/FlightStream.java

@@ -37,7 +37,7 @@
 import org.apache.arrow.vector.FieldVector;
 import org.apache.arrow.vector.VectorLoader;
 import org.apache.arrow.vector.VectorSchemaRoot;
-import org.apache.arrow.vector.dictionary.Dictionary;
+import org.apache.arrow.vector.dictionary.BaseDictionary;
 import org.apache.arrow.vector.dictionary.DictionaryProvider;
 import org.apache.arrow.vector.ipc.message.ArrowDictionaryBatch;
 import org.apache.arrow.vector.ipc.message.ArrowRecordBatch;
@@ -268,7 +268,7 @@ public boolean next() {
               if (dictionaries == null) {
                 throw new IllegalStateException("Dictionary ownership was claimed by the application.");
               }
-              final Dictionary dictionary = dictionaries.lookup(id);
+              final BaseDictionary dictionary = dictionaries.lookup(id);
               if (dictionary == null) {
                 throw new IllegalArgumentException("Dictionary not defined in schema: ID " + id);
               }
@@ -410,12 +410,12 @@ public void onNext(ArrowMessage msg) {
           }
 
           final List<Field> fields = new ArrayList<>();
-          final Map<Long, Dictionary> dictionaryMap = new HashMap<>();
+          final Map<Long, BaseDictionary> dictionaryMap = new HashMap<>();
           for (final Field originalField : schema.getFields()) {
             final Field updatedField = DictionaryUtility.toMemoryFormat(originalField, allocator, dictionaryMap);
             fields.add(updatedField);
           }
-          for (final Map.Entry<Long, Dictionary> entry : dictionaryMap.entrySet()) {
+          for (final Map.Entry<Long, BaseDictionary> entry : dictionaryMap.entrySet()) {
             dictionaries.put(entry.getValue());
           }
           schema = new Schema(fields, schema.getCustomMetadata());

java/memory/memory-core/src/test/java/org/apache/arrow/memory/util/TestArrowBufPointer.java

@@ -206,7 +206,7 @@ public int hashCode(ArrowBuf buf, long offset, long length) {
 
     @Override
     public int hashCode(byte[] buf, int offset, int length) {
-      return 0;
+      throw new UnsupportedOperationException("Not used in UT.");
     }
 
     @Override

java/memory/memory-core/src/test/java/org/apache/arrow/memory/util/hash/TestArrowBufHasher.java

@@ -150,11 +150,11 @@ private void verifyHashCodeNotEqual(ArrowBuf buf1, byte[] ba1, int offset1, int
   @Parameterized.Parameters(name = "hasher = {0}")
   public static Collection<Object[]> getHasher() {
     return Arrays.asList(
-        new Object[] {SimpleHasher.class.getSimpleName(),
-            SimpleHasher.INSTANCE},
-        new Object[] {MurmurHasher.class.getSimpleName(),
-            new MurmurHasher()
-        }
+      new Object[] {SimpleHasher.class.getSimpleName(),
+        SimpleHasher.INSTANCE},
+      new Object[] {MurmurHasher.class.getSimpleName(),
+        new MurmurHasher()
+      }
     );
   }
 }

java/tools/src/test/java/org/apache/arrow/tools/EchoServerTest.java

@@ -40,6 +40,7 @@
 import org.apache.arrow.vector.VectorSchemaRoot;
 import org.apache.arrow.vector.complex.ListVector;
 import org.apache.arrow.vector.complex.impl.UnionListWriter;
+import org.apache.arrow.vector.dictionary.BaseDictionary;
 import org.apache.arrow.vector.dictionary.Dictionary;
 import org.apache.arrow.vector.dictionary.DictionaryProvider;
 import org.apache.arrow.vector.dictionary.DictionaryProvider.MapDictionaryProvider;
@@ -207,7 +208,7 @@ public void testFlatDictionary() throws IOException {
         Assert.assertEquals(1, readVector.getObject(4));
         Assert.assertEquals(2, readVector.getObject(5));
 
-        Dictionary dictionary = reader.lookup(1L);
+        BaseDictionary dictionary = reader.lookup(1L);
         Assert.assertNotNull(dictionary);
         VarCharVector dictionaryVector = ((VarCharVector) dictionary.getVector());
         Assert.assertEquals(3, dictionaryVector.getValueCount());
@@ -289,7 +290,7 @@ public void testNestedDictionary() throws IOException {
         Assert.assertEquals(Arrays.asList(0), readVector.getObject(1));
         Assert.assertEquals(Arrays.asList(1), readVector.getObject(2));
 
-        Dictionary readDictionary = reader.lookup(2L);
+        BaseDictionary readDictionary = reader.lookup(2L);
         Assert.assertNotNull(readDictionary);
         VarCharVector dictionaryVector = ((VarCharVector) readDictionary.getVector());
         Assert.assertEquals(2, dictionaryVector.getValueCount());

java/vector/src/main/java/org/apache/arrow/vector/dictionary/BaseDictionary.java

@@ -0,0 +1,48 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.arrow.vector.dictionary;
+
+import org.apache.arrow.vector.FieldVector;
+import org.apache.arrow.vector.types.pojo.ArrowType;
+import org.apache.arrow.vector.types.pojo.DictionaryEncoding;
+
+/**
+ * Base interface for various dictionary implementations. Implementations include
+ * {@link Dictionary} for encoding a complete vector and {@link BatchedDictionary}
+ * for continuous encoding of a vector.
+ * These methods provide means of accessing the dictionary vector containing the
+ * encoded data.
+ */
+public interface BaseDictionary {
+
+  /**
+   * The dictionary vector containing unique entries.
+   */
+  FieldVector getVector();
+
+  /**
+   * The encoding used for the dictionary vector.
+   */
+  DictionaryEncoding getEncoding();
+
+  /**
+   * The type of the dictionary vector.
+   */
+  ArrowType getVectorType();
+
+}