Following the discussion on making UUID data type to be much more liberal ( http://archives.postgresql.org/pgsql-hackers/2008-02/msg01214.php ) I have decided to try to approach it from more general perspective.
The current state of code is available at: http://qnex.net/hexstring-0.1-2008-03-03.tgz And now for more details: The idea is to have a data type HEXSTRING(n) which can have an optional typemod specifying the size of data (in bytes). Internally the datatype is binary compatible with bytea, but I/O is done as hex-encoded strings. The format is liberal, isspace() and ispunct() characters are skipped while the digits are read. I have played with two versions of hexstringin() function, one which uses strtoul() function and the other which uses "home brew" code. The latter appears to be faster, so I stayed with that. But I would appreciate comments on this from more experienced. So, what are the use cases? CREATE DOMAIN liberal_uuid AS hexstring(16); CREATE DOMAIN liberal_macaddr AS hexstring(6); ...it allows for creating other standard hex-types, as for example: CREATE DOMAIN wwn AS hexstring(8); -- http://en.wikipedia.org/wiki/World_Wide_Name Also it can be a convenient alternative to bytea format (I know, the encode()/decode() pair), especially when you have to format output data as some fancy hex-string. The code is currently just a bunch of input/output/typemod functions which appear to work. I will add casts, operators, etc -- they most likely will be nicked from bytea. What I would like to also add is ubiquitous to_char(hex, format) function. For an UUID-compatilbe format it would be called as: SELECT to_char(hex, 'xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx') or SELECT to_char(hex, '8x-4x-4x-4x-12x') where x is expanded as [0-9a-f] digit and X is expanded as [0-9A-F]. I am not sure what to do about variable length hexstrings, I am considering something like to_char(hex, '8X-') which would produce something like '00000000-11111111-22222222' for a 12-byte hexstring (what to do about dangling '-' ?). ...but the original case against liberal UUID was that it would make the I/O slower. My simple test: postgres=# CREATE TABLE uuids AS SELECT uuid_generate_v4()::text AS u FROM generate_series(1,10000000); CREATE postgres=# CREATE TEMP TABLE text ON COMMIT DROP AS SELECT u::hexstring(16) FROM uuids; SELECT Time: 13058.486 ms postgres=# CREATE TEMP TABLE test ON COMMIT DROP AS SELECT u::uuid FROM uuids; SELECT Time: 13536.816 ms ...now hexstring is varlena type but does not use strtoul. Perhaps uuid might be more liberal too. What do you think about it? Regards, Dawid -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your Subscription: http://mail.postgresql.org/mj/mj_wwwusr?domain=postgresql.org&extra=pgsql-hackers
