ARROW-257: Add a typeids Vector to Union type

format/Message.fbs

@@ -23,8 +23,13 @@ table List {
 
 enum UnionMode:short { Sparse, Dense }
 
+/// A union is a complex type with children in Field
+/// By default ids in the type vector refer to the offsets in the children
+/// optionally typeIds provides an indirection between the child offset and the type id
+/// for each child typeIds[offset] is the id used in the type vector
 table Union {
   mode: UnionMode;
+  typeIds: [ int ]; // optional, describes typeid of each child.
 }
 
 table Int {

java/vector/src/main/codegen/data/ArrowTypes.tdd

@@ -30,7 +30,7 @@
     },
     {
       name: "Union",
-      fields: [{name: "mode", type: short}]
+      fields: [{name: "mode", type: short}, {name: "typeIds", type: "int[]"}]
     },
     {
       name: "Int",

java/vector/src/main/codegen/templates/ArrowType.java

@@ -33,12 +33,23 @@
 
 import java.util.Objects;
 
+/**
+ * Arrow types
+ **/
 public abstract class ArrowType {
 
   public abstract byte getTypeType();
   public abstract int getType(FlatBufferBuilder builder);
   public abstract <T> T accept(ArrowTypeVisitor<T> visitor);
 
+  /**
+   * to visit the ArrowTypes
+   * <code>
+   *   type.accept(new ArrowTypeVisitor<Type>() {
+   *   ...
+   *   });
+   * </code>
+   */
   public static interface ArrowTypeVisitor<T> {
   <#list arrowTypes.types as type>
     T visit(${type.name} type);
@@ -55,9 +66,7 @@ public static class ${name} extends ArrowType {
     </#if>
 
     <#list fields as field>
-    <#assign fieldName = field.name>
-    <#assign fieldType = field.type>
-    ${fieldType} ${fieldName};
+    ${field.type} ${field.name};
     </#list>
 
     <#if type.fields?size != 0>
@@ -79,6 +88,9 @@ public int getType(FlatBufferBuilder builder) {
       <#if field.type == "String">
       int ${field.name} = builder.createString(this.${field.name});
       </#if>
+      <#if field.type == "int[]">
+      int ${field.name} = org.apache.arrow.flatbuf.${type.name}.create${field.name?cap_first}Vector(builder, this.${field.name});
+      </#if>
       </#list>
       org.apache.arrow.flatbuf.${type.name}.start${type.name}(builder);
       <#list type.fields as field>
@@ -96,7 +108,7 @@ public int getType(FlatBufferBuilder builder) {
     public String toString() {
       return "${name}{"
       <#list fields as field>
-      + ", " + ${field.name}
+        + <#if field.type == "int[]">java.util.Arrays.toString(${field.name})<#else>${field.name}</#if><#if field_has_next> + ", " </#if>
       </#list>
       + "}";
     }
@@ -115,8 +127,7 @@ public boolean equals(Object obj) {
       return true;
       <#else>
       ${type.name} that = (${type.name}) obj;
-      return
-      <#list type.fields as field>Objects.equals(this.${field.name}, that.${field.name}) <#if field_has_next>&&<#else>;</#if>
+      return <#list type.fields as field>Objects.deepEquals(this.${field.name}, that.${field.name}) <#if field_has_next>&&<#else>;</#if>
       </#list>
       </#if>
     }
@@ -134,9 +145,20 @@ public static org.apache.arrow.vector.types.pojo.ArrowType getTypeForField(org.a
     <#assign name = type.name>
     <#assign nameLower = type.name?lower_case>
     <#assign fields = type.fields>
-    case Type.${type.name}:
+    case Type.${type.name}: {
       org.apache.arrow.flatbuf.${type.name} ${nameLower}Type = (org.apache.arrow.flatbuf.${type.name}) field.type(new org.apache.arrow.flatbuf.${type.name}());
-      return new ${type.name}(<#list type.fields as field>${nameLower}Type.${field.name}()<#if field_has_next>, </#if></#list>);
+      <#list type.fields as field>
+      <#if field.type == "int[]">
+      ${field.type} ${field.name} = new int[${nameLower}Type.${field.name}Length()];
+      for (int i = 0; i< ${field.name}.length; ++i) {
+        ${field.name}[i] = ${nameLower}Type.${field.name}(i);
+      }
+      <#else>
+      ${field.type} ${field.name} = ${nameLower}Type.${field.name}();
+      </#if>
+      </#list>
+      return new ${type.name}(<#list type.fields as field>${field.name}<#if field_has_next>, </#if></#list>);
+    }
     </#list>
     default:
       throw new UnsupportedOperationException("Unsupported type: " + field.typeType());

java/vector/src/main/codegen/templates/UnionVector.java

@@ -232,10 +232,13 @@ public void clear() {
   @Override
   public Field getField() {
     List<org.apache.arrow.vector.types.pojo.Field> childFields = new ArrayList<>();
-    for (ValueVector v : internalMap.getChildren()) {
+    List<FieldVector> children = internalMap.getChildren();
+    int[] typeIds = new int[children.size()];
+    for (ValueVector v : children) {
+      typeIds[childFields.size()] = v.getMinorType().ordinal();
       childFields.add(v.getField());
     }
-    return new Field(name, true, new ArrowType.Union(Sparse), childFields);
+    return new Field(name, true, new ArrowType.Union(Sparse, typeIds), childFields);
   }
 
   @Override

java/vector/src/main/java/org/apache/arrow/vector/types/Types.java

@@ -472,7 +472,7 @@ public FieldWriter getNewFieldWriter(ValueVector vector) {
         return new UnionListWriter((ListVector) vector);
       }
     },
-    UNION(new Union(UnionMode.Sparse)) {
+    UNION(new Union(UnionMode.Sparse, null)) {
       @Override
       public Field getField() {
         throw new UnsupportedOperationException("Cannot get simple field for Union type");

java/vector/src/test/java/org/apache/arrow/vector/pojo/TestConvert.java

@@ -22,11 +22,12 @@
 import static org.junit.Assert.assertEquals;
 
 import org.apache.arrow.flatbuf.UnionMode;
+import org.apache.arrow.vector.types.Types.MinorType;
 import org.apache.arrow.vector.types.pojo.ArrowType.FloatingPoint;
 import org.apache.arrow.vector.types.pojo.ArrowType.Int;
 import org.apache.arrow.vector.types.pojo.ArrowType.List;
-import org.apache.arrow.vector.types.pojo.ArrowType.Timestamp;
 import org.apache.arrow.vector.types.pojo.ArrowType.Struct_;
+import org.apache.arrow.vector.types.pojo.ArrowType.Timestamp;
 import org.apache.arrow.vector.types.pojo.ArrowType.Union;
 import org.apache.arrow.vector.types.pojo.ArrowType.Utf8;
 import org.apache.arrow.vector.types.pojo.Field;
@@ -78,7 +79,7 @@ public void nestedSchema() {
     childrenBuilder.add(new Field("child4", true, new List(), ImmutableList.<Field>of(
         new Field("child4.1", true, Utf8.INSTANCE, null)
         )));
-    childrenBuilder.add(new Field("child5", true, new Union(UnionMode.Sparse), ImmutableList.<Field>of(
+    childrenBuilder.add(new Field("child5", true, new Union(UnionMode.Sparse, new int[] { MinorType.TIMESTAMP.ordinal(), MinorType.FLOAT8.ordinal() } ), ImmutableList.<Field>of(
         new Field("child5.1", true, new Timestamp("UTC"), null),
         new Field("child5.2", true, new FloatingPoint(DOUBLE), ImmutableList.<Field>of())
         )));