private void allocateArrays(int count) {
    isConvert = new boolean[count];
    projectionColumnNums = new int[count];
    targetTypeInfos = new TypeInfo[count];
    maxLengths = new int[count];
  }
This class assigns specified columns of a row from a Writable row objects.

The caller provides the data types and projection column numbers of a subset of the columns
to assign.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/VectorAssignRow.java