Confusion over Python drivers
in [PgSql]
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From: Florian Weimer on 14 Feb 2010 14:43 * Jeff Davis: > Agreed. Ultimately, the conversion has to be done somewhere, but I don't > believe the driver is the place for it. Type conversions are always > going to be imperfect, and this has some important consequences: > * The type conversion system will be endlessly tweaked to improve it > * Developers will always run into problems with it in any complex > application, so we need to allow them to circumvent the system and do it > themselves when necessary. The downside is that passing strings up to the application may have distinctly worse performance characteristics than passing a number. > In ruby-pg, you can just do: > > conn.exec("INSERT INTO foo VALUES($1)", ["Jeff"]) > > And I think that's appropriate. What I'm saying is that there should > still exist some way to pass explicit types or formats (although that > should still be easier than it is in C ;). Here's the long form: > > conn.exec("INSERT INTO foo VALUES($1)", > [{:value => "Jeff", :format => 0, :type => 0}]) Okay, this isn't too bad an API. I will use the same approach. In my case, it means no transparent support for arrays, but per your own guidelines, this is okay. > That copies value so that foo and bar have the same contents: a 4 byte > value "\000". What would happen though, if val was transparently > decoded? It would decode it once in ruby, and again inside of postgres > (in byteain), leaving you with a one byte value in bar, even though foo > has a four-byte value. I've never viewed it from this angle, and I agree that it makes sense. Thanks for your observations and explanations, they were helpful. -- Sent via pgsql-hackers mailing list (pgsql-hackers(a)postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
From: Jeff Davis on 15 Feb 2010 22:48
On Sun, 2010-02-14 at 20:43 +0100, Florian Weimer wrote: > The downside is that passing strings up to the application may have > distinctly worse performance characteristics than passing a number. Yes, that is a good point. I tried to clarify this in the doc. I think this would fall under the optional type conversion convenience functions. As long as it's explicit that the conversion is happening, I think it's OK. Regards, Jeff Davis -- Sent via pgsql-hackers mailing list (pgsql-hackers(a)postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers |