On 10/10/2009 01:14 AM, tsuraan wrote:
The most significant impact is that it takes up twice as much space,
including the primary key index. This means fewer entries per block,
which means slower scans and/or more blocks to navigate through. Still,
compared to the rest of the overhead of an index row or a table row, it
is low - I think it's more important to understand whether you can get
away with using a sequential integer, in which case UUID is unnecessary
overhead - or whether you are going to need UUID anyways. If you need
UUID anyways - having two primary keys is probably not worth it.
Ok, that's what I was hoping. Out of curiosity, is there a preferred
way to store 256-bit ints in postgres? At that point, is a bytea the
most reasonable choice, or is there a better way to do it?
Do you need to be able to do queries on it? Numeric should be able to
store 256-bit integers.
If you don't need to do queries on it, an option I've considered in the
past is to break it up into 4 x int64. Before UUID was supported, I had
seriously considered storing UUID as 2 x int64. Now that UUID is
supported, you might also abuse UUID where 1 x 256-bit = 2 x UUID.
If you want it to be seemless and fully optimal, you would introduce a
new int256 type (or whatever the name of the type you are trying to
represent). Adding new types to PostgreSQL is not that hard. This would
allow queries (=, <>, <, >) as well.
Cheers,
mark
--
Mark Mielke<mark@xxxxxxxxx>
--
Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-performance
