F.47. uuid-ossp

F.47. uuid-ossp
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F.47.1. uuid-ossp Functions

The uuid-ossp module provides functions to generate universally unique identifiers (UUIDs) using one of several standard algorithms. There are also functions to produce certain special UUID constants. This module is only necessary for special requirements beyond what is available in core LightDB. See Section 10.13 for built-in ways to generate UUIDs.

This module is considered “trusted”, that is, it can be installed by non-superusers who have CREATE privilege on the current database.

F.47.1. `uuid-ossp` Functions

Table F.73 shows the functions available to generate UUIDs. The relevant standards ITU-T Rec. X.667, ISO/IEC 9834-8:2005, and RFC 4122 specify four algorithms for generating UUIDs, identified by the version numbers 1, 3, 4, and 5. (There is no version 2 algorithm.) Each of these algorithms could be suitable for a different set of applications.

Table F.73. Functions for UUID Generation

Function Description
`uuid_generate_v1` () → `uuid` Generates a version 1 UUID. This involves the MAC address of the computer and a time stamp. Note that UUIDs of this kind reveal the identity of the computer that created the identifier and the time at which it did so, which might make it unsuitable for certain security-sensitive applications.
`uuid_generate_v1mc` () → `uuid` Generates a version 1 UUID, but uses a random multicast MAC address instead of the real MAC address of the computer.
`uuid_generate_v3` ( `namespace` `uuid`, `name` `text` ) → `uuid` Generates a version 3 UUID in the given namespace using the specified input name. The namespace should be one of the special constants produced by the `uuid_ns_*()` functions shown in Table F.74. (It could be any UUID in theory.) The name is an identifier in the selected namespace. For example: SELECT uuid_generate_v3(uuid_ns_url(), 'https://light-pg.com'); The name parameter will be MD5-hashed, so the cleartext cannot be derived from the generated UUID. The generation of UUIDs by this method has no random or environment-dependent element and is therefore reproducible.
`uuid_generate_v4` () → `uuid` Generates a version 4 UUID, which is derived entirely from random numbers.
`sys_guid` () → `uuid` Generates a version 4 UUID, which is derived entirely from random numbers. Equivalent with function `uuid_generate_v4`.
`uuid_generate_v5` ( `namespace` `uuid`, `name` `text` ) → `uuid` Generates a version 5 UUID, which works like a version 3 UUID except that SHA-1 is used as a hashing method. Version 5 should be preferred over version 3 because SHA-1 is thought to be more secure than MD5.

Function

Description

uuid_generate_v1 () → uuid

Generates a version 1 UUID. This involves the MAC address of the computer and a time stamp. Note that UUIDs of this kind reveal the identity of the computer that created the identifier and the time at which it did so, which might make it unsuitable for certain security-sensitive applications.

uuid_generate_v1mc () → uuid

Generates a version 1 UUID, but uses a random multicast MAC address instead of the real MAC address of the computer.

uuid_generate_v3 ( namespace uuid, name text ) → uuid

Generates a version 3 UUID in the given namespace using the specified input name. The namespace should be one of the special constants produced by the uuid_ns_*() functions shown in Table F.74. (It could be any UUID in theory.) The name is an identifier in the selected namespace.

For example:

SELECT uuid_generate_v3(uuid_ns_url(), 'https://light-pg.com');

The name parameter will be MD5-hashed, so the cleartext cannot be derived from the generated UUID. The generation of UUIDs by this method has no random or environment-dependent element and is therefore reproducible.

uuid_generate_v4 () → uuid

Generates a version 4 UUID, which is derived entirely from random numbers.

sys_guid () → uuid

Generates a version 4 UUID, which is derived entirely from random numbers. Equivalent with function uuid_generate_v4.

uuid_generate_v5 ( namespace uuid, name text ) → uuid

Generates a version 5 UUID, which works like a version 3 UUID except that SHA-1 is used as a hashing method. Version 5 should be preferred over version 3 because SHA-1 is thought to be more secure than MD5.

Table F.74. Functions Returning UUID Constants

Function Description
`uuid_nil` () → `uuid` Returns a “nil” UUID constant, which does not occur as a real UUID.
`uuid_ns_dns` () → `uuid` Returns a constant designating the DNS namespace for UUIDs.
`uuid_ns_url` () → `uuid` Returns a constant designating the URL namespace for UUIDs.
`uuid_ns_oid` () → `uuid` Returns a constant designating the ISO object identifier (OID) namespace for UUIDs. (This pertains to ASN.1 OIDs, which are unrelated to the OIDs used in LightDB.)
`uuid_ns_x500` () → `uuid` Returns a constant designating the X.500 distinguished name (DN) namespace for UUIDs.

Function

Description

uuid_nil () → uuid

Returns a “nil” UUID constant, which does not occur as a real UUID.

uuid_ns_dns () → uuid

Returns a constant designating the DNS namespace for UUIDs.

uuid_ns_url () → uuid

Returns a constant designating the URL namespace for UUIDs.

uuid_ns_oid () → uuid

Returns a constant designating the ISO object identifier (OID) namespace for UUIDs. (This pertains to ASN.1 OIDs, which are unrelated to the OIDs used in LightDB.)

uuid_ns_x500 () → uuid

Returns a constant designating the X.500 distinguished name (DN) namespace for UUIDs.

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F.47. uuid-ossp

F.47.1. uuid-ossp Functions

F.47.1. `uuid-ossp` Functions