public String toString() {
      StringBuilder builder = new StringBuilder();
      builder.append(String.format(
          "OutputColumnManager: initialOutputCol: %d, outputColCount: %d, usedOutputColumns#: %d"
              + ", reuseScratchColumns: %s, output cols:",
          initialOutputCol, outputColCount, usedOutputColumns.size(), reuseScratchColumns));
      for (int i = 0; i < outputColCount; i++) {
        builder.append(String.format(
            "\n%d (%d): used: %s, scratchVectorTypeName: %s" + ", physicalVariation: %s, trackWasUsed: %s", i,
            i + initialOutputCol, usedOutputColumns.contains(i), scratchVectorTypeNames[i],
            scratchDataTypePhysicalVariations[i], scratchColumnTrackWasUsed[i]));
      }
      return builder.toString();
    }
Context class for vectorization execution.
Main role is to map column names to column indices and serves as a
factory class for building vectorized expressions out of descriptors.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/VectorizationContext.java