Michael Bayer <mike_mp <at> zzzcomputing.com> writes: > > > On Nov 1, 2011, at 7:23 AM, Paul wrote: > > > What's the cleanest way to perform a multiple insert or update? ie, if the record > > already exists an update operation is performed or if not an insert is performed. > > that's a funny usage of terminology - a "multiple" insert would normally be construed as meaning an INSERT > that has many rows at once, which is a different issue. > > As I read this I wasn't clear what you were asking for, the "MERGE" SQL construct, or just asking about ORM > merge. After I wrote a whole reply here based on the SQL construct I realized you were talking about the ORM. > > If you have a bunch of objects, all of which you can populate with their primary key, and you'd like some to > result in INSERTS and others in UPDATE, then yes you can use Session.merge() in a loop. I would try to > pre-load all the existing rows, if possible, into a temporary collection - ideally limited to those rows > you know you're operating upon. That would make the operation of Session.merge() much faster as it can > locate each object in the local identity map rather than emitting a SELECT > for each one. >
Ah thanks, I'm not entirely sure how I would pre-load the rows. Would I just use a query to select the rows in the same session somewhere before? Do I need to store these returned instances somewhere? -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
