feat(bigquery): add ArrowDeserializer helper utility

java-bigquery/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/ArrowDeserializer.java

@@ -0,0 +1,205 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Licensed 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 com.google.cloud.bigquery;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.io.BaseEncoding;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Locale;
+import org.apache.arrow.memory.BufferAllocator;
+import org.apache.arrow.memory.RootAllocator;
+import org.apache.arrow.vector.FieldVector;
+import org.apache.arrow.vector.VectorLoader;
+import org.apache.arrow.vector.VectorSchemaRoot;
+import org.apache.arrow.vector.complex.ListVector;
+import org.apache.arrow.vector.complex.StructVector;
+import org.apache.arrow.vector.ipc.ReadChannel;
+import org.apache.arrow.vector.ipc.message.MessageSerializer;
+import org.apache.arrow.vector.types.pojo.ArrowType;
+import org.apache.arrow.vector.types.pojo.Field;
+import org.apache.arrow.vector.util.ByteArrayReadableSeekableByteChannel;
+
+final class ArrowDeserializer {
+
+  private ArrowDeserializer() {}
+
+  static Schema arrowSchemaToBigQuerySchema(org.apache.arrow.vector.types.pojo.Schema arrowSchema) {
+    List<com.google.cloud.bigquery.Field> fields = new ArrayList<>();
+    for (Field arrowField : arrowSchema.getFields()) {
+      fields.add(arrowFieldToBigQueryField(arrowField));
+    }
+    return Schema.of(fields);
+  }
+
+  private static com.google.cloud.bigquery.Field arrowFieldToBigQueryField(Field arrowField) {
+    String name = arrowField.getName();
+    ArrowType type = arrowField.getType();
+    com.google.cloud.bigquery.Field.Builder builder;
+
+    if (type instanceof ArrowType.List) {
+      Field innerField = arrowField.getChildren().get(0);
+      LegacySQLTypeName innerType = arrowTypeToLegacySQLTypeName(innerField.getType());
+      builder = com.google.cloud.bigquery.Field.newBuilder(name, innerType);
+      builder.setMode(com.google.cloud.bigquery.Field.Mode.REPEATED);
+      if (!innerField.getChildren().isEmpty()) {
+        List<com.google.cloud.bigquery.Field> subFields = new ArrayList<>();
+        for (Field childField : innerField.getChildren()) {
+          subFields.add(arrowFieldToBigQueryField(childField));
+        }
+        builder.setType(LegacySQLTypeName.RECORD, FieldList.of(subFields));
+      }
+    } else {
+      LegacySQLTypeName bqType = arrowTypeToLegacySQLTypeName(type);
+      builder = com.google.cloud.bigquery.Field.newBuilder(name, bqType);
+      if (arrowField.isNullable()) {
+        builder.setMode(com.google.cloud.bigquery.Field.Mode.NULLABLE);
+      } else {
+        builder.setMode(com.google.cloud.bigquery.Field.Mode.REQUIRED);
+      }
+      if (!arrowField.getChildren().isEmpty()) {
+        List<com.google.cloud.bigquery.Field> subFields = new ArrayList<>();
+        for (Field childField : arrowField.getChildren()) {
+          subFields.add(arrowFieldToBigQueryField(childField));
+        }
+        builder.setType(LegacySQLTypeName.RECORD, FieldList.of(subFields));
+      }
+    }
+    return builder.build();
+  }
+
+  private static LegacySQLTypeName arrowTypeToLegacySQLTypeName(ArrowType type) {
+    switch (type.getTypeID()) {
+      case Int:
+        return LegacySQLTypeName.INTEGER;
+      case FloatingPoint:
+        return LegacySQLTypeName.FLOAT;
+      case Utf8:
+        return LegacySQLTypeName.STRING;
+      case Bool:
+        return LegacySQLTypeName.BOOLEAN;
+      case Binary:
+        return LegacySQLTypeName.BYTES;
+      case Decimal:
+        return LegacySQLTypeName.NUMERIC;
+      case Timestamp:
+        return LegacySQLTypeName.TIMESTAMP;
+      case Date:
+        return LegacySQLTypeName.DATE;
+      case Time:
+        return LegacySQLTypeName.TIME;
+      case Struct:
+        return LegacySQLTypeName.RECORD;
+      default:
+        throw new IllegalArgumentException("Unsupported Arrow type: " + type.getTypeID());
+    }
+  }
+
+  static List<FieldValueList> deserializeRecordBatch(
+      byte[] recordBatchBytes, Schema schema, org.apache.arrow.vector.types.pojo.Schema arrowSchema)
+      throws IOException {
+    try (BufferAllocator allocator = new RootAllocator(Long.MAX_VALUE)) {
+      List<FieldVector> vectors = new ArrayList<>();
+      for (Field field : arrowSchema.getFields()) {
+        vectors.add(field.createVector(allocator));
+      }
+      try (VectorSchemaRoot root = new VectorSchemaRoot(vectors)) {
+        VectorLoader loader = new VectorLoader(root);
+        try (org.apache.arrow.vector.ipc.message.ArrowRecordBatch deserializedBatch =
+            MessageSerializer.deserializeRecordBatch(
+                new ReadChannel(new ByteArrayReadableSeekableByteChannel(recordBatchBytes)),
+                allocator)) {
+          loader.load(deserializedBatch);
+          int rowCount = root.getRowCount();
+          List<FieldValueList> rows = new ArrayList<>(rowCount);
+          for (int i = 0; i < rowCount; i++) {
+            rows.add(arrowRootToFieldValueList(root, i, schema));
+          }
+          return ImmutableList.copyOf(rows);
+        }
+      }
+    }
+  }
+
+  static FieldValueList arrowRootToFieldValueList(
+      VectorSchemaRoot root, int rowIndex, Schema schema) {
+    List<FieldValue> fieldValues = new ArrayList<>();
+    for (int colIndex = 0; colIndex < root.getFieldVectors().size(); colIndex++) {
+      FieldVector vector = root.getVector(colIndex);
+      com.google.cloud.bigquery.Field bqField = schema.getFields().get(colIndex);
+      fieldValues.add(arrowVectorToFieldValue(vector, rowIndex, bqField));
+    }
+    return FieldValueList.of(fieldValues, schema.getFields());
+  }
+
+  private static FieldValue arrowVectorToFieldValue(
+      FieldVector vector, int rowIndex, com.google.cloud.bigquery.Field bqField) {
+    if (vector.isNull(rowIndex)) {
+      return FieldValue.of(FieldValue.Attribute.PRIMITIVE, null);
+    }
+
+    // Handle repeated fields
+    if (bqField.getMode() == com.google.cloud.bigquery.Field.Mode.REPEATED) {
+      ListVector listVector = (ListVector) vector;
+      FieldVector dataVector = (FieldVector) listVector.getDataVector();
+      int start = listVector.getElementStartIndex(rowIndex);
+      int end = listVector.getElementEndIndex(rowIndex);
+      List<FieldValue> elements = new ArrayList<>(end - start);
+      com.google.cloud.bigquery.Field elementBqField =
+          com.google.cloud.bigquery.Field.newBuilder(bqField.getName(), bqField.getType())
+              .setMode(com.google.cloud.bigquery.Field.Mode.NULLABLE)
+              .build();
+      for (int k = start; k < end; k++) {
+        elements.add(arrowVectorToFieldValue(dataVector, k, elementBqField));
+      }
+      return FieldValue.of(
+          FieldValue.Attribute.REPEATED, FieldValueList.of(elements, bqField.getSubFields()));
+    }
+
+    // Handle RECORD/STRUCT fields
+    if (bqField.getType() == LegacySQLTypeName.RECORD) {
+      StructVector structVector = (StructVector) vector;
+      List<FieldValue> elements = new ArrayList<>(structVector.size());
+      for (int colIndex = 0; colIndex < structVector.size(); colIndex++) {
+        FieldVector childVector = (FieldVector) structVector.getChildByOrdinal(colIndex);
+        com.google.cloud.bigquery.Field childBqField = bqField.getSubFields().get(colIndex);
+        elements.add(arrowVectorToFieldValue(childVector, rowIndex, childBqField));
+      }
+      return FieldValue.of(
+          FieldValue.Attribute.RECORD, FieldValueList.of(elements, bqField.getSubFields()));
+    }
+
+    // Handle primitive types - convert everything to String representations to match BQ standard
+    Object value = vector.getObject(rowIndex);
+    String stringVal;
+    if (value instanceof byte[]) {
+      stringVal = BaseEncoding.base64().encode((byte[]) value);
+    } else if (bqField.getType() == LegacySQLTypeName.TIMESTAMP) {
+      // Arrow timestamps are long values representing epoch micro/milli/nano seconds.
+      // Standard BigQuery JSON returns timestamps as string of epoch seconds with micro precision
+      // (e.g. "1408452095.220000").
+      long micros = (long) value;
+      // Convert to seconds with 6 decimal places of precision
+      stringVal = String.format(Locale.US, "%.6f", micros / 1000000.0);
+    } else {
+      stringVal = String.valueOf(value);
+    }
+
+    return FieldValue.of(FieldValue.Attribute.PRIMITIVE, stringVal);
+  }
+}