public Type getMapKeyType() throws HCatException {
    assertTypeInCategory(this.type, Category.MAP, this.fieldName);
    return mapKeyType;
  }
@deprecated as of 0.13, slated for removal with 0.15
use {@link #getMapKeyTypeInfo()} instead
hcatalog/core/src/main/java/org/apache/hive/hcatalog/data/schema/HCatFieldSchema.java