[GitHub] [iceberg] rdblue commented on a change in pull request #3023: Arrow: Support DecimalType

[GitBox <gi...@apache.org>]

rdblue commented on a change in pull request #3023:
URL: https://github.com/apache/iceberg/pull/3023#discussion_r712399768



##########
File path: arrow/src/main/java/org/apache/iceberg/arrow/DictEncodedArrowConverter.java
##########
@@ -0,0 +1,64 @@
+/*
+ * 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.iceberg.arrow;
+
+import java.math.BigDecimal;
+import org.apache.arrow.vector.DecimalVector;
+import org.apache.arrow.vector.FieldVector;
+import org.apache.iceberg.arrow.vectorized.ArrowVectorAccessor;
+import org.apache.iceberg.arrow.vectorized.VectorHolder;
+import org.apache.iceberg.relocated.com.google.common.base.Preconditions;
+import org.apache.iceberg.types.Type;
+import org.apache.iceberg.types.Types;
+
+/**
+ * This converts dictionary encoded arrow vectors to a correctly typed arrow vector.
+ */
+public class DictEncodedArrowConverter {
+
+  private DictEncodedArrowConverter() {
+  }
+
+  public static FieldVector toArrowVector(VectorHolder vectorHolder, ArrowVectorAccessor<?, String, ?, ?> accessor) {
+    Preconditions.checkArgument(null != vectorHolder, "VectorHolder cannot be null");
+    Preconditions.checkArgument(null != accessor, "ArrowVectorAccessor cannot be null");
+    // TODO: add conversions for other types (https://github.com/apache/iceberg/issues/2484)
+    if (vectorHolder.isDictionaryEncoded()) {
+      if (Type.TypeID.DECIMAL.equals(vectorHolder.icebergType().typeId())) {
+        int precision = ((Types.DecimalType) vectorHolder.icebergType()).precision();
+        int scale = ((Types.DecimalType) vectorHolder.icebergType()).scale();
+
+        DecimalVector decimalVector = new DecimalVector(
+            vectorHolder.vector().getName(),
+            ArrowSchemaUtil.convert(vectorHolder.icebergField()).getFieldType(),
+            vectorHolder.vector().getAllocator());

Review comment:
       I don't think that this should be doing any allocation. We should pass in the correct vector and this should just fill it with data. That way, we can control allocation and reuse buffers.




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