HIVE-1360. It has been a long-standing request for UDFs to be able to

ql/src/java/org/apache/hadoop/hive/ql/exec/ExprNodeConstantEvaluator.java

@@ -20,10 +20,8 @@
 
 import org.apache.hadoop.hive.ql.metadata.HiveException;
 import org.apache.hadoop.hive.ql.plan.ExprNodeConstantDesc;
+import org.apache.hadoop.hive.serde2.objectinspector.ConstantObjectInspector;
 import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
-import org.apache.hadoop.hive.serde2.objectinspector.PrimitiveObjectInspector.PrimitiveCategory;
-import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorFactory;
-import org.apache.hadoop.hive.serde2.typeinfo.PrimitiveTypeInfo;
 
 /**
  * ExprNodeConstantEvaluator.
@@ -32,19 +30,11 @@
 public class ExprNodeConstantEvaluator extends ExprNodeEvaluator {
 
   protected ExprNodeConstantDesc expr;
-  transient ObjectInspector writableObjectInspector;
-  transient Object writableValue;
+  transient ConstantObjectInspector writableObjectInspector;
 
   public ExprNodeConstantEvaluator(ExprNodeConstantDesc expr) {
     this.expr = expr;
-    PrimitiveCategory pc = ((PrimitiveTypeInfo) expr.getTypeInfo())
-        .getPrimitiveCategory();
-    writableObjectInspector = PrimitiveObjectInspectorFactory
-        .getPrimitiveWritableObjectInspector(pc);
-    // Convert from Java to Writable
-    writableValue = PrimitiveObjectInspectorFactory
-        .getPrimitiveJavaObjectInspector(pc).getPrimitiveWritableObject(
-        expr.getValue());
+    writableObjectInspector = expr.getWritableObjectInspector();
   }
 
   @Override
@@ -54,7 +44,7 @@ public ObjectInspector initialize(ObjectInspector rowInspector) throws HiveExcep
 
   @Override
   public Object evaluate(Object row) throws HiveException {
-    return writableValue;
+    return writableObjectInspector.getWritableConstantValue();
   }
 
 }

ql/src/java/org/apache/hadoop/hive/ql/exec/FunctionRegistry.java

@@ -164,6 +164,7 @@
 import org.apache.hadoop.hive.ql.udf.generic.GenericUDFMap;
 import org.apache.hadoop.hive.ql.udf.generic.GenericUDFMapKeys;
 import org.apache.hadoop.hive.ql.udf.generic.GenericUDFMapValues;
+import org.apache.hadoop.hive.ql.udf.generic.GenericUDFNamedStruct;
 import org.apache.hadoop.hive.ql.udf.generic.GenericUDFOPAnd;
 import org.apache.hadoop.hive.ql.udf.generic.GenericUDFOPEqual;
 import org.apache.hadoop.hive.ql.udf.generic.GenericUDFOPEqualOrGreaterThan;
@@ -404,6 +405,7 @@ public final class FunctionRegistry {
     registerGenericUDF("array", GenericUDFArray.class);
     registerGenericUDF("map", GenericUDFMap.class);
     registerGenericUDF("struct", GenericUDFStruct.class);
+    registerGenericUDF("named_struct", GenericUDFNamedStruct.class);
     registerGenericUDF("create_union", GenericUDFUnion.class);
 
     registerGenericUDF("case", GenericUDFCase.class);

ql/src/java/org/apache/hadoop/hive/ql/plan/ExprNodeConstantDesc.java

@@ -21,6 +21,10 @@
 import java.io.Serializable;
 
 import org.apache.hadoop.hive.serde.Constants;
+import org.apache.hadoop.hive.serde2.objectinspector.ConstantObjectInspector;
+import org.apache.hadoop.hive.serde2.objectinspector.PrimitiveObjectInspector.PrimitiveCategory;
+import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorFactory;
+import org.apache.hadoop.hive.serde2.typeinfo.PrimitiveTypeInfo;
 import org.apache.hadoop.hive.serde2.typeinfo.TypeInfo;
 import org.apache.hadoop.hive.serde2.typeinfo.TypeInfoFactory;
 
@@ -52,6 +56,19 @@ public Object getValue() {
     return value;
   }
 
+  @Override
+  public ConstantObjectInspector getWritableObjectInspector() {
+    PrimitiveCategory pc = ((PrimitiveTypeInfo)getTypeInfo())
+        .getPrimitiveCategory();
+    // Convert from Java to Writable
+    Object writableValue = PrimitiveObjectInspectorFactory
+        .getPrimitiveJavaObjectInspector(pc).getPrimitiveWritableObject(
+          getValue());
+    return PrimitiveObjectInspectorFactory
+        .getPrimitiveWritableConstantObjectInspector(pc, writableValue);
+  }
+
+
   @Override
   public String toString() {
     return "Const " + typeInfo.toString() + " " + value;

ql/src/java/org/apache/hadoop/hive/ql/plan/ExprNodeDesc.java

@@ -23,6 +23,8 @@
 
 import org.apache.hadoop.hive.ql.lib.Node;
 import org.apache.hadoop.hive.serde2.typeinfo.TypeInfo;
+import org.apache.hadoop.hive.serde2.typeinfo.TypeInfoUtils;
+import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
 
 /**
  * ExprNodeDesc.
@@ -64,6 +66,11 @@ public String getExprString() {
     return null;
   }
 
+  public ObjectInspector getWritableObjectInspector() {
+    return TypeInfoUtils
+      .getStandardWritableObjectInspectorFromTypeInfo(typeInfo);
+  }
+
   @Explain(displayName = "type")
   public String getTypeString() {
     return typeInfo.getTypeName();

ql/src/java/org/apache/hadoop/hive/ql/plan/ExprNodeGenericFuncDesc.java

@@ -145,9 +145,7 @@ public static ExprNodeGenericFuncDesc newInstance(GenericUDF genericUDF,
       List<ExprNodeDesc> children) throws UDFArgumentException {
     ObjectInspector[] childrenOIs = new ObjectInspector[children.size()];
     for (int i = 0; i < childrenOIs.length; i++) {
-      childrenOIs[i] = TypeInfoUtils
-          .getStandardWritableObjectInspectorFromTypeInfo(children.get(i)
-          .getTypeInfo());
+      childrenOIs[i] = children.get(i).getWritableObjectInspector();
     }
 
     ObjectInspector oi = genericUDF.initialize(childrenOIs);

ql/src/java/org/apache/hadoop/hive/ql/udf/generic/GenericUDFNamedStruct.java

@@ -0,0 +1,89 @@
+/**
+ * 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.hadoop.hive.ql.udf.generic;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+
+import org.apache.hadoop.hive.ql.exec.UDFArgumentException;
+import org.apache.hadoop.hive.ql.exec.UDFArgumentLengthException;
+import org.apache.hadoop.hive.ql.exec.UDFArgumentTypeException;
+import org.apache.hadoop.hive.ql.exec.Description;
+import org.apache.hadoop.hive.ql.metadata.HiveException;
+import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
+import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorFactory;
+import org.apache.hadoop.hive.serde2.objectinspector.primitive.WritableConstantStringObjectInspector;
+import org.apache.hadoop.hive.serde2.objectinspector.StructObjectInspector;
+
+@Description(name = "named_struct",
+    value = "_FUNC_(name1, val1, name2, val2, ...) - Creates a struct with the given " +
+            "field names and values")
+public class GenericUDFNamedStruct extends GenericUDF {
+  Object[] ret;
+
+  @Override
+  public ObjectInspector initialize(ObjectInspector[] arguments)
+      throws UDFArgumentException {
+
+    int numFields = arguments.length;
+    if (numFields % 2 == 1) {
+      throw new UDFArgumentLengthException(
+          "NAMED_STRUCT expects an even number of arguments.");
+    }
+    ret = new Object[numFields / 2];
+
+    ArrayList<String> fname = new ArrayList<String>(numFields / 2);
+    ArrayList<ObjectInspector> retOIs = new ArrayList<ObjectInspector>(numFields / 2);
+    for (int f = 0; f < numFields; f+=2) {
+      if (!(arguments[f] instanceof WritableConstantStringObjectInspector)) {
+        throw new UDFArgumentTypeException(f, "Even arguments" + 
+            " to NAMED_STRUCT must be a constant STRING." + arguments[f].toString());
+      }
+      WritableConstantStringObjectInspector constantOI = 
+        (WritableConstantStringObjectInspector)arguments[f];
+      fname.add(constantOI.getWritableConstantValue().toString());
+      retOIs.add(arguments[f + 1]);
+    }
+    StructObjectInspector soi = 
+      ObjectInspectorFactory.getStandardStructObjectInspector(fname, retOIs);
+    return soi;
+  }
+
+  @Override
+  public Object evaluate(DeferredObject[] arguments) throws HiveException {
+    for (int i = 0; i < arguments.length / 2; i++) {
+      ret[i] = arguments[2 * i + 1].get();
+    }
+    return ret;
+  }
+
+  @Override
+  public String getDisplayString(String[] children) {
+    StringBuilder sb = new StringBuilder();
+    sb.append("named_struct(");
+    for (int i = 0; i < children.length; i++) {
+      if (i > 0) {
+        sb.append(',');
+      }
+      sb.append(children[i]);
+    }
+    sb.append(')');
+    return sb.toString();
+  }
+}

ql/src/test/queries/clientpositive/udf_named_struct.q

@@ -0,0 +1,9 @@
+DESCRIBE FUNCTION named_struct;
+DESCRIBE FUNCTION EXTENDED named_struct;
+
+EXPLAIN
+SELECT named_struct("foo", 1, "bar", 2), 
+       named_struct("foo", 1, "bar", 2).foo FROM src LIMIT 1;
+
+SELECT named_struct("foo", 1, "bar", 2), 
+       named_struct("foo", 1, "bar", 2).foo FROM src LIMIT 1;

ql/src/test/results/clientpositive/show_functions.q.out

@@ -97,6 +97,7 @@ max
 min
 minute
 month
+named_struct
 negative
 ngrams
 not

ql/src/test/results/clientpositive/udf_named_struct.q.out

@@ -0,0 +1,63 @@
+PREHOOK: query: DESCRIBE FUNCTION named_struct
+PREHOOK: type: DESCFUNCTION
+POSTHOOK: query: DESCRIBE FUNCTION named_struct
+POSTHOOK: type: DESCFUNCTION
+named_struct(name1, val1, name2, val2, ...) - Creates a struct with the given field names and values
+PREHOOK: query: DESCRIBE FUNCTION EXTENDED named_struct
+PREHOOK: type: DESCFUNCTION
+POSTHOOK: query: DESCRIBE FUNCTION EXTENDED named_struct
+POSTHOOK: type: DESCFUNCTION
+named_struct(name1, val1, name2, val2, ...) - Creates a struct with the given field names and values
+PREHOOK: query: EXPLAIN
+SELECT named_struct("foo", 1, "bar", 2), 
+       named_struct("foo", 1, "bar", 2).foo FROM src LIMIT 1
+PREHOOK: type: QUERY
+POSTHOOK: query: EXPLAIN
+SELECT named_struct("foo", 1, "bar", 2), 
+       named_struct("foo", 1, "bar", 2).foo FROM src LIMIT 1
+POSTHOOK: type: QUERY
+ABSTRACT SYNTAX TREE:
+  (TOK_QUERY (TOK_FROM (TOK_TABREF (TOK_TABNAME src))) (TOK_INSERT (TOK_DESTINATION (TOK_DIR TOK_TMP_FILE)) (TOK_SELECT (TOK_SELEXPR (TOK_FUNCTION named_struct "foo" 1 "bar" 2)) (TOK_SELEXPR (. (TOK_FUNCTION named_struct "foo" 1 "bar" 2) foo))) (TOK_LIMIT 1)))
+
+STAGE DEPENDENCIES:
+  Stage-1 is a root stage
+  Stage-0 is a root stage
+
+STAGE PLANS:
+  Stage: Stage-1
+    Map Reduce
+      Alias -> Map Operator Tree:
+        src 
+          TableScan
+            alias: src
+            Select Operator
+              expressions:
+                    expr: named_struct('foo',1,'bar',2)
+                    type: struct<foo:int,bar:int>
+                    expr: named_struct('foo',1,'bar',2).foo
+                    type: int
+              outputColumnNames: _col0, _col1
+              Limit
+                File Output Operator
+                  compressed: false
+                  GlobalTableId: 0
+                  table:
+                      input format: org.apache.hadoop.mapred.TextInputFormat
+                      output format: org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat
+
+  Stage: Stage-0
+    Fetch Operator
+      limit: 1
+
+
+PREHOOK: query: SELECT named_struct("foo", 1, "bar", 2), 
+       named_struct("foo", 1, "bar", 2).foo FROM src LIMIT 1
+PREHOOK: type: QUERY
+PREHOOK: Input: default@src
+PREHOOK: Output: file:/var/folders/C4/C40caRNsEM4C4yVangruonVUe7Y/-Tmp-/jonchang/hive_2011-08-11_01-02-24_658_503462155153078291/-mr-10000
+POSTHOOK: query: SELECT named_struct("foo", 1, "bar", 2), 
+       named_struct("foo", 1, "bar", 2).foo FROM src LIMIT 1
+POSTHOOK: type: QUERY
+POSTHOOK: Input: default@src
+POSTHOOK: Output: file:/var/folders/C4/C40caRNsEM4C4yVangruonVUe7Y/-Tmp-/jonchang/hive_2011-08-11_01-02-24_658_503462155153078291/-mr-10000
+{"foo":1,"bar":2}	1

serde/src/java/org/apache/hadoop/hive/serde2/objectinspector/ConstantObjectInspector.java

@@ -0,0 +1,29 @@
+/**
+ * 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.hadoop.hive.serde2.objectinspector;
+
+/**
+ * ConstantObjectInspector.  This interface should be implemented by
+ * ObjectInspectors which represent constant values and can return them without
+ * an evaluation.
+ */
+public interface ConstantObjectInspector extends ObjectInspector {
+
+  Object getWritableConstantValue(); 
+
+}

serde/src/java/org/apache/hadoop/hive/serde2/objectinspector/primitive/PrimitiveObjectInspectorFactory.java

@@ -20,10 +20,19 @@
 
 import java.util.HashMap;
 
+import org.apache.hadoop.hive.serde2.objectinspector.ConstantObjectInspector;
 import org.apache.hadoop.hive.serde2.objectinspector.PrimitiveObjectInspector;
 import org.apache.hadoop.hive.serde2.objectinspector.PrimitiveObjectInspector.PrimitiveCategory;
 import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorUtils.PrimitiveTypeEntry;
 import org.apache.hadoop.io.Writable;
+import org.apache.hadoop.io.BooleanWritable;
+import org.apache.hadoop.io.ByteWritable;
+import org.apache.hadoop.hive.serde2.io.ShortWritable;
+import org.apache.hadoop.io.IntWritable;
+import org.apache.hadoop.io.LongWritable;
+import org.apache.hadoop.io.FloatWritable;
+import org.apache.hadoop.hive.serde2.io.DoubleWritable;
+import org.apache.hadoop.io.Text;
 
 /**
  * PrimitiveObjectInspectorFactory is the primary way to create new
@@ -136,6 +145,40 @@ public static AbstractPrimitiveWritableObjectInspector getPrimitiveWritableObjec
     return result;
   }
 
+  /**
+   * Returns a PrimitiveWritableObjectInspector which implements ConstantObjectInspector 
+   * for the PrimitiveCategory.
+   * 
+   * @param primitiveCategory
+   * @param value
+   */
+  public static ConstantObjectInspector getPrimitiveWritableConstantObjectInspector(
+      PrimitiveCategory primitiveCategory, Object value) {
+    switch (primitiveCategory) {
+    case BOOLEAN:
+      return new WritableConstantBooleanObjectInspector((BooleanWritable)value);
+    case BYTE:
+      return new WritableConstantByteObjectInspector((ByteWritable)value);
+    case SHORT:
+      return new WritableConstantShortObjectInspector((ShortWritable)value);
+    case INT:
+      return new WritableConstantIntObjectInspector((IntWritable)value);
+    case LONG:
+      return new WritableConstantLongObjectInspector((LongWritable)value);
+    case FLOAT:
+      return new WritableConstantFloatObjectInspector((FloatWritable)value);
+    case DOUBLE:
+      return new WritableConstantDoubleObjectInspector((DoubleWritable)value);
+    case STRING:
+      return new WritableConstantStringObjectInspector((Text)value);
+    case VOID:
+      return new WritableConstantVoidObjectInspector();
+    default:
+      throw new RuntimeException("Internal error: Cannot find "
+        + "ConstantObjectInspector for " + primitiveCategory);
+    }
+  }
+
   /**
    * Returns the PrimitiveJavaObjectInspector for the PrimitiveCategory.
    *