![]() ![]() More than one of these libraries might be available on a particular machine, so configure does not automatically choose one. When invoking configure, specify -with-uuid=bsd to use the BSD functions, or -with-uuid=e2fs to use e2fsprogs' libuuid, or -with-uuid=ossp to use the OSSP UUID library. On Linux, macOS, and some other platforms, suitable functions are provided in the libuuid library, which originally came from the e2fsprogs project (though on modern Linux it is considered part of util-linux-ng). On FreeBSD and some other BSD-derived platforms, suitable UUID creation functions are included in the core libc library. But to generate a UUID value, such as to establish a default value for a column, you need a Postgres extension (a plugin). To build UUID values, the CREATE Extension query must be used to input the. uuid-ossp can now be built without the OSSP library on some platforms. The resultant UUID values for a column are stored in the PostgreSQL UUID datatype. While the OSSP UUID library can still be found at, it is not well maintained, and is becoming increasingly difficult to port to newer platforms. Historically this module depended on the OSSP UUID library, which accounts for the module's name. The PostgreSQL documentation says that UUID generation relies on the OSSP library.A look at the source code of OSSP (version 1.6.2) shows that the code uses /dev/urandom on Unix-like systems (CryptGenRandom() on Windows), and also a much weaker PRNG based on current time, process ID, and the C library rand() function. Version 5 should be preferred over version 3 because SHA-1 is thought to be more secure than MD5. Generates a version 5 UUID, which works like a version 3 UUID except that SHA-1 is used as a hashing method. Uuid_generate_v5 ( namespace uuid, name text ) → uuid Generates a version 4 UUID, which is derived entirely from random numbers. The generation of UUIDs by this method has no random or environment-dependent element and is therefore reproducible. ![]() The name parameter will be MD5-hashed, so the cleartext cannot be derived from the generated UUID. SELECT uuid_generate_v3(uuid_ns_url(), '') ![]() (It could be any UUID in theory.) The name is an identifier in the selected namespace. Generate a UUID as PostgreSQL default value CREATE EXTENSION IF NOT EXISTS pgcrypto SELECT genrandomuuid() id UUID NOT NULL DEFAULT genrandomuuid(). The namespace should be one of the special constants produced by the uuid_ns_*() functions shown in Table F.33. Generates a version 3 UUID in the given namespace using the specified input name. Uuid_generate_v3 ( namespace uuid, name text ) → uuid Generates a version 1 UUID, but uses a random multicast MAC address instead of the real MAC address of the computer. 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. This involves the MAC address of the computer and a time stamp. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |