Re: Primary keys and speed
От | Joe Conway |
---|---|
Тема | Re: Primary keys and speed |
Дата | |
Msg-id | 000201c1399c$6d60b3e0$0705a8c0@jecw2k1 обсуждение исходный текст |
Ответ на | Primary keys and speed (Rob Brown-Bayliss <on_the_net@clear.net.nz>) |
Список | pgsql-general |
> > I am looking at useing uuid's as primary keys rather than a normal > > sequence of numbers. > > > > The uuids are long text strings like so: > > > > 7559e648-a29c-11d5-952f-00c026a18838 > > > > The reason for useing them is that it's almost gaurenteed that > > imported data from another site is going to have a unique identifier. > > > > But I was wondering if this will impact on the speed of the database. > > > > In the long run the application does not need to be blindingly fast as 99% > > of the time it is waiting on human interaction. > > > > Any ideas? > > I have not done *comparative* studies of using these kind of strings versus sequence numbers, but I have done a fair amount of this sort of thing in one of the applications I've been working on. On old hardware (dual ppro 200 with 512MB and RAID5) I got lookups times at around 10 milliseconds, from a table with 20 million records. The key was a 40 byte hex string. The timing was from running "set show_query_stats = true;" and then looking at the tail of the postgres serverlog. My best advice is to load some sample data in your schema on your hardware and give it a try. Hope this helps, -- Joe
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