Universally Unique Identifiers (UUID).
For formal definition see RFC 4122 and ISO/IEC 9834-8:2005.
Object has a globally unique property
represented by a UUID value.
Return a version 1 UUID.
The algorithm uses a random multicast MAC address instead of the real MAC address of the computer.
The UUID will contain 47 random bits, 60 bits representing the current time, and 14 bits of clock sequence that may be used to ensure uniqueness. The rest of the bits indicate the version of the UUID.
This is the default function used to populate the
Return a version 4 UUID.
The UUID is derived entirely from random numbers: it will contain 122 random bits and 6 version bits.
It is permitted to override the
default of the
with a call to this function, but this should be done with
caution: fully random ids will be less clustered than time-based id,
which may lead to worse index performance.