PGUUID Document

1, uuid
	uuid newid() --һTime_baseUUID.
	uuid newid(n) -- n=0 һnil uuid, n = 1 һTime_base uuid,
n=4һrandom_base uuid
	
	ע: PGUUIDɵUUIDDECʽ

2, Ƚϲ(<, >, =, <>, >= ,<=)
   ע, Ƚϲǰַ˳Ƚuuid

3, Ĺܺ
   int2 uuid_type(uuid)
		ָuuid
			0, nil uuid
			1, time-base
			4, random-base

   int2 uuid_variant(uuid)
		uuidvariant
			0. NCS
			1. DEC
			2. Micosoft
			3. Other

	timestamp uuid_timestamp(time-uuid)
		time-base uuid Ĵʱ

		ע:
			˺ֻtime-baseuuidЧ,nil uuid, random-base  name-base ䷵ֵûж
