Support declaring primary key columns as ASC/DESC to determine row key order about phoenix

[jtaylor-sfdc]

Support the following syntax:

CREATE TABLE foo (
    host_name varchar,
    created_date date
    constraint my_pk primary key (host_name ASC, created_date DESC));

also this:

CREATE TABLE foo (
    id varchar PRIMARY KEY DESC,
    created_date date);

By default, the row key order would be ascending, but this could be overridden as shown above.

The implementation should all be mostly isolated to PDataType. However, the sort order would need to be stored in the SYSTEM.TABLE metadata table, in the row representing the column. The order value would cached in PColumn and passed through the PDataType methods. Check out the elegant way that Orderly does the writing, by having a mask on an Order enum and xor-ing like this:

/** The sort order of a row key, ascending or descending. */
public enum Order
{
  ASCENDING((byte)0),
  DESCENDING((byte)0xff);
  private final byte mask;
  Order(byte mask) { this.mask = mask; }
  /** Gets the byte mask associated with the sort order. When a 
   * serialized byte is XOR'd with the mask, the result is the same byte 
   * but sorted in the direction specified by the Order object. 
   * @see RowKey#serialize
   */
  byte mask() { return mask; }
}
public class FixedIntWritableRowKey extends RowKey
{
  private IntWritable iw;
  @Override
  public Class getSerializedClass() { return IntWritable.class; }
  @Override
  public int getSerializedLength(Object o) throws IOException {
    return Bytes.SIZEOF_INT;
  }
  @Override
  public void serialize(Object o, ImmutableBytesWritable w)
    throws IOException
  {
    byte[] b = w.get();
    int offset = w.getOffset();
    int i = ((IntWritable)o).get();
    Bytes.putInt(b, offset, i ^ Integer.MIN_VALUE ^ order.mask());
    RowKeyUtils.seek(w, Bytes.SIZEOF_INT);
  }
  @Override
  public void skip(ImmutableBytesWritable w) throws IOException {
    RowKeyUtils.seek(w, Bytes.SIZEOF_INT);
  }
  @Override
  public Object deserialize(ImmutableBytesWritable w) throws IOException {
    int offset = w.getOffset();
    byte[] s = w.get();
    int i = Bytes.toInt(s, offset) ^ Integer.MIN_VALUE ^ order.mask();
    RowKeyUtils.seek(w, Bytes.SIZEOF_INT);
    if (iw == null)
      iw = new IntWritable();
    iw.set(i);
    return iw;
  }
}

[jtaylor-sfdc]

Fixed by @simontoens, with a new record of a 78 file change list for his first Phoenix contribution! Thanks for the awesome work.