Github user paul-rogers commented on a diff in the pull request:
https://github.com/apache/drill/pull/1112#discussion_r168682152
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/record/metadata/MetadataUtils.java
---
@@ -0,0 +1,165 @@
+/*
+ * 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.drill.exec.record.metadata;
+
+import java.util.List;
+
+import org.apache.drill.common.types.TypeProtos.DataMode;
+import org.apache.drill.common.types.TypeProtos.MinorType;
+import org.apache.drill.exec.record.BatchSchema;
+import org.apache.drill.exec.record.MaterializedField;
+
+public class MetadataUtils {
+
+ public static TupleSchema fromFields(Iterable<MaterializedField> fields)
{
+ TupleSchema tuple = new TupleSchema();
+ for (MaterializedField field : fields) {
+ tuple.add(field);
+ }
+ return tuple;
+ }
+
+ /**
+ * Create a column metadata object that holds the given
+ * {@link MaterializedField}. The type of the object will be either a
+ * primitive or map column, depending on the field's type. The logic
+ * here mimics the code as written, which is very messy in some places.
+ *
+ * @param field the materialized field to wrap
+ * @return the column metadata that wraps the field
+ */
+
+ public static AbstractColumnMetadata fromField(MaterializedField field) {
+ MinorType type = field.getType().getMinorType();
+ switch (type) {
+ case MAP:
+ return MetadataUtils.newMap(field);
+ case UNION:
+ if (field.getType().getMode() != DataMode.OPTIONAL) {
+ throw new UnsupportedOperationException(type.name() + " type must
be nullable");
+ }
+ return new VariantColumnMetadata(field);
+ case LIST:
+ switch (field.getType().getMode()) {
+ case OPTIONAL:
+
+ // List of unions (or a degenerate union of a single type.)
+ // Not supported in Drill.
--- End diff --
We do. This comment is in the wrong place, should be in default.
---
