From: Dan Janowski <danj@3skel.com>
Date: 2004-09-01T00:53:03+09:00
Subject: Re: [Ruby-DBI-devel] Common Last Index Method

Postgres returns an OID as a result of INSERT statements. It is in-band 
with the execution. It may be the only DB that does this and is the 
most compelling case. Support for auto-increment is easy as you 
illustrate. As for Oracle and other DBs that require the pre-fetch of 
sequences for that kind of tracking, it is probably better to leave 
get_last_rowid as raise "unimplemented".

Dan



On Aug 31, 2004, at 10:34, Brian Candler wrote:

> However, my experience is limited mainly to oracle, mysql and sqlite 
> (in
> particular I've hardly used pgsql at all) so I don't know how 
> widespread the
> ability to "give me the primary key for the most recently-inserted 
> row" is.
>
> I would be quite happy if DBD::Foo had a "get_last_rowid" method, which
> would not exist in the base class, so would raise an exception if you 
> tried
> to use it on some other database which doesn't support this idea.
>
> But I think this is an example of something which fits the 
> extensible-DBD
> concept nicely:
>
>   module DBD
>     class Mysql
>       def get_last_rowid
>         select_one("select last_insert_id()")[0]
>       end
>     end
>     class Sqlite
>       def get_last_rowid
>         select_one("select last_insert_rowid()")[0].to_i
>       end
>     end
>   end
>
> Note that Sqlite returns everything as strings, so an integer column 
> returns
> "1234" instead of 1234. That adds further difficultly to making code
> portable between databases :-(