[sqlalchemy] Re: Is there a way to replace object in DB? - braydon fuller - com.googlegroups.sqlalchemy

15 messages in com.googlegroups.sqlalchemy[sqlalchemy] Re: Is there a way to re...

From	Sent On	Attachments
Denis S. Otkidach	26 Dec 2007 09:12
Michael Bayer	26 Dec 2007 11:38
Denis S. Otkidach	27 Dec 2007 01:11
Michael Bayer	27 Dec 2007 13:58
Rick Morrison	27 Dec 2007 13:59
braydon fuller	27 Dec 2007 15:01
Rick Morrison	27 Dec 2007 15:06
Denis S. Otkidach	28 Dec 2007 02:49
Michael Bayer	28 Dec 2007 07:25
Denis S. Otkidach	11 Jan 2008 09:30
Michael Bayer	11 Jan 2008 09:41
Denis S. Otkidach	15 Jan 2008 05:20
Michael Bayer	15 Jan 2008 07:54
Denis S. Otkidach	16 Jan 2008 01:43
Michael Bayer	16 Jan 2008 08:41

Subject:	[sqlalchemy] Re: Is there a way to replace object in DB?
From:	braydon fuller (cour...@braydon.com)
Date:	12/27/2007 03:01:06 PM
List:	com.googlegroups.sqlalchemy

you can also use 'try' to avoid error messages:

def ensure_object(db, id): try: o = db.Query(ModelObject).get(id) except: o = ModelObject(1, u'title') db.save(o) db.commit() return o

-Braydon

Rick Morrison wrote:

...if you're just checking to see if something exists in the database, why not just try to .load() it, and then construct it afresh if you don't find it?

This kind of operation is sometimes called an "upsert" ...some database engines support it, some don't. Most don't. But what all database engines DO support is a query, followed by either an insert, or an update as appropriate.

Here's the idiom that should work:

def ensure_object(sess, id): o = sess.Query(ModelObject).get(id) # if found, o is now loaded into session if not o: o = ModelObject(1, u'title' sess.save(o) sess.flush() return o