title: Why using integer type for partition key can minimize memory usage?
body: <blockquote>
  <p>Use smallest appropriate integer types for partition key columns.Although it is tempting to use strings for partition key columns,
  since those values are turned into HDFS directory names anyway, you
  can minimize memory usage by using numeric values for common partition
  key fields such as YEAR, MONTH, and DAY. Use the smallest integer type
  that holds the appropriate range of values, typically TINYINT for
  MONTH and DAY, and SMALLINT for YEAR. Use the EXTRACT() function to
  pull out individual date and time fields from a TIMESTAMP value, and
  CAST() the return value to the appropriate integer type.</p>
  </blockquote>
  <p>The above paragraph comes from Cloudera. Why using integer type for partition key can minimize memory usage? Just because of the HDFS file name?</p>