Re: EOF inserts PK automatically
Re: EOF inserts PK automatically
- Subject: Re: EOF inserts PK automatically
- From: "Ruenagel, Frank" <email@hidden>
- Date: Mon, 22 Nov 2004 10:00:56 +0100
Hi Chuck,
I really love your contributions. They have often helped me.
But in this case IMHO it *is* possible to get WO running with
identity columns. True is that you cannot use the standard
mechanisms for insert (and I guess you mean that).
In case of insert into a table with a identity-column EOF has to be
informed about the pk which is not created by itself. EOF has to
be forced to stay away from any insert.
EOUtilties.ObjectForPrimaryKey works fine with PKs EOF has not
seen before, because he makes a database roundtrip in this case and
creates the object for you:
1. You want to insert an new record
2. Execute a stored procecure which inserts a new record and
gives back its primary key. I use a marker in a special column
to find the newly created record after insert.
3. Create the EO with EOUtilities.objectWithPrimaryKeyValue
Dear Chuck, are there any reasons why this should not work?
Best regards
Frank
>
> Perhaps it is worth wading into this one more time. Using database
> generated unique numbers (a.k.a. sequences) is not a problem. As
> Benjamin points out below, it is just a matter of some code in the
> plugin or even in your app as a delegate method to one of
> the EOAccess
> classed (I forget which off the top of my head and am too
> lazy to look
> it up).
>
> Another way that databases generate the primary key is what is often
> referred to as an identity column. The values in this column are
> filled in by the database when the row is inserted. The method of
> primary key generation can NOT be used with WO, or any other
> environment that does not use some proprietary database
> access method.
> If you think about it you will quickly see why it won't work.
> You have
> some data, but no primary key. You insert it, and the PK is
> created by
> the database and added to the data. But _you_ are never told
> what the
> PK is. SQL INSERT only returns a success or failure code, not a copy
> of the inserted data. So now you have the data, but not the primary
> key (which you have no way of knowing) and the database has the same
> data _and_ the primary key. Now, how are you going to update that
> exact row if you don't know the PK? You could the row where all the
> other values are the same, but there is no guarantee that
> this defines
> a unique row. In many, many cases it does not define a
> unique row, it
> defines a set of rows. How are you going to know which one
> the the one
> you just inserted? In a nutshell, you can't.
>
> Your only hope for using this with WO is to:
> 1. Somehow force it to not generate the PK and use null as the insert
> value. If the database takes 0 as null, then this is easy
> 2. After insertion _immediately_ tell the ec to forget the
> object (not
> invalidate, forget).
> 3. The user will then have to somehow fetch some data that includes
> this new object.
>
> Me, I'd stay far away from that.
>
> Chuck
>
>
> On Nov 19, 2004, at 10:58 AM, Benjamin J Doherty wrote:
>
> > On Nov 19, 2004, at 3:33 AM, Sako! wrote:
> >
> >> if you read my first or second post, you will mention i use MS-SQL.
> >> and tipically Apple talks about all the world ECCEPT MS-SQL.
> >> "Apple hates Microsoft" why do i wonder?
> >>
> >> Mention this sentence in the site:
> >> " It doesn't work if the database includes rows that are
> inserted by
> >> non-Enterprise Objects applications."
> >> so what the hell do i have as a solution then? non.
> >> this sentence tells me i have to forget the PK feature in EOF.
> >> Ok fine. my first question was and still: how can i force
> EOF to stop
> >> trying to use this week pk feature(s)?
> >>
> >
> > I don't know ANYTHING about MS-SQL, but I assume that like most
> > databases it has some support for sequences. If you want
> to use these
> > instead of that (agreed) weak EO_PK_TABLE, just subclass the MS-SQL
> > adapter, rework the code from the PostgresqlPlugIn from
> Project Wonder
> > (which uses sequences to generate primary keys), and voilà sommes
> > nous.
> >
> > But I wasn't following the whole discussion, so I admit I
> may not be
> > on the nose here.
> >
> > Benjamin J Doherty
> > sole proprietor
> > !&# Group
> > www.bangpound.org
> > +1-773-934-4236
> --
> Practical WebObjects - a book for intermediate WebObjects developers
> who want to increase their overall knowledge of WebObjects, or those
> who are trying to solve specific application development problems.
> http://www.global-village.net/products/practical_webobjects
>
>
>
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