private MapOpCtx initObjectInspector(Configuration hconf, MapOpCtx opCtx,
      StructObjectInspector tableRowOI) throws Exception {
    PartitionDesc pd = opCtx.partDesc;
    TableDesc td = pd.getTableDesc();

    // Use table properties in case of unpartitioned tables,
    // and the union of table properties and partition properties, with partition
    // taking precedence, in the case of partitioned tables
    Properties overlayedProps =
        SerDeUtils.createOverlayedProperties(td.getProperties(), pd.getProperties());

    Map<String, String> partSpec = pd.getPartSpec();
    opCtx.tableName = String.valueOf(overlayedProps.getProperty("name"));
    opCtx.partName = String.valueOf(partSpec);
    opCtx.deserializer = pd.getDeserializer(hconf);

    StructObjectInspector partRawRowObjectInspector;
    boolean isAcid = AcidUtils.isTablePropertyTransactional(td.getProperties());
    if (Utilities.isSchemaEvolutionEnabled(hconf, isAcid) && Utilities.isInputFileFormatSelfDescribing(pd)) {
      partRawRowObjectInspector = tableRowOI;
    } else {
      partRawRowObjectInspector =
          (StructObjectInspector) opCtx.deserializer.getObjectInspector();
    }

    opCtx.partTblObjectInspectorConverter =
        ObjectInspectorConverters.getConverter(partRawRowObjectInspector, tableRowOI);

    // Next check if this table has partitions and if so
    // get the list of partition names as well as allocate
    // the serdes for the partition columns
    String pcols = overlayedProps.getProperty(hive_metastoreConstants.META_TABLE_PARTITION_COLUMNS);

    if (pcols != null && pcols.length() > 0) {
      String[] partKeys = pcols.trim().split("/");
      String pcolTypes = overlayedProps
          .getProperty(hive_metastoreConstants.META_TABLE_PARTITION_COLUMN_TYPES);
      String[] partKeyTypes = pcolTypes.trim().split(":");

      if (partKeys.length > partKeyTypes.length) {
          throw new HiveException("Internal error : partKeys length, " +partKeys.length +
                  " greater than partKeyTypes length, " + partKeyTypes.length);
      }

      List<String> partNames = new ArrayList<String>(partKeys.length);
      Object[] partValues = new Object[partKeys.length];
      List<ObjectInspector> partObjectInspectors = new ArrayList<ObjectInspector>(partKeys.length);

      for (int i = 0; i < partKeys.length; i++) {
        String key = partKeys[i];
        partNames.add(key);
        ObjectInspector oi = PrimitiveObjectInspectorFactory.getPrimitiveWritableObjectInspector
            (TypeInfoFactory.getPrimitiveTypeInfo(partKeyTypes[i]));

        // Partitions do not exist for this table
        if (partSpec == null) {
          // for partitionless table, initialize partValue to null
          partValues[i] = null;
        } else {
            partValues[i] =
                ObjectInspectorConverters.
                getConverter(PrimitiveObjectInspectorFactory.
                    javaStringObjectInspector, oi).convert(partSpec.get(key));
        }
        partObjectInspectors.add(oi);
      }
      opCtx.rowWithPart = new Object[] {null, partValues};
      opCtx.partObjectInspector = ObjectInspectorFactory
          .getStandardStructObjectInspector(partNames, partObjectInspectors);
    }

    // The op may not be a TableScan for mapjoins
    // Consider the query: select /*+MAPJOIN(a)*/ count(*) FROM T1 a JOIN T2 b ON a.key = b.key;
    // In that case, it will be a Select, but the rowOI need not be amended
    if (opCtx.op instanceof TableScanOperator) {
      TableScanOperator tsOp = (TableScanOperator) opCtx.op;
      TableScanDesc tsDesc = tsOp.getConf();
      if (tsDesc != null && tsDesc.hasVirtualCols()) {
        opCtx.vcs = tsDesc.getVirtualCols();
        opCtx.vcValues = new Object[opCtx.vcs.size()];
        opCtx.vcsObjectInspector = VirtualColumn.getVCSObjectInspector(opCtx.vcs);
        if (opCtx.isPartitioned()) {
          opCtx.rowWithPartAndVC = Arrays.copyOfRange(opCtx.rowWithPart, 0, 3);
        } else {
          opCtx.rowWithPartAndVC = new Object[2];
        }
      }
    }
    if (!opCtx.hasVC() && !opCtx.isPartitioned()) {
      opCtx.rowObjectInspector = tableRowOI;
      return opCtx;
    }
    List<StructObjectInspector> inspectors = new ArrayList<StructObjectInspector>();
    inspectors.add(tableRowOI);
    if (opCtx.isPartitioned()) {
      inspectors.add(opCtx.partObjectInspector);
    }
    if (opCtx.hasVC()) {
      inspectors.add(opCtx.vcsObjectInspector);
    }
    opCtx.rowObjectInspector = ObjectInspectorFactory.getUnionStructObjectInspector(inspectors);
    return opCtx;
  }
Initializes this map op as the root of the tree. It sets JobConf &
MapRedWork and starts initialization of the operator tree rooted at this
op.

@param hconf
@param mapWork
@throws HiveException
ql/src/java/org/apache/hadoop/hive/ql/exec/MapOperator.java