Subject [IBO] Re: TIBOTable.Insert then Edit
Author kgdonn
Helen, I deeply appreciate your information here, even the
criticism :-)

The thing to keep in mind is that many of us bought IBO exactly
because we're porting away from the BDE. Unfortunately, ten years
ago when I started this application, I wasn't as smart as I am now
and I wrote a lot of code that doesn't make sense for the IBO world
whether or not it ever made sense for the Paradox world. And yet,
unavoidably, that's the code I get to port now. It might be true
that a small application can change a few class derivations, do some
search and replace, and be ported to IBO, but a ten-year-old
application with hundreds of thousands of lines of code doesn't come
along quite as easily. I'm trying to build a portability layer that
lets most of the application stay the same while making the move to
IBO. I'd like to take care of most performance and incompatibility
issues there, but I recognize that some parts of the app will simply
have to change. The trick is figuring out which is which.

I'll take the info you've provided me and see if I can apply it to
my current problem. Thanks much!


--- In, Helen Borrie <helebor@t...> wrote:
> At 03:53 PM 6/12/2005 +0000, you wrote:
> >I haven't seen a response to this. Let me ask a simpler question.
> >Is it possible to succesfully carry out the sequence Insert, Post,
> >Edit (same record), Post with a TIBOTable?
> Depends on what you mean by "success". Can you do it? yes.
Should you do
> it? No. You can win the battle, but you will lose the war.
> More comments inline.....
> >Thanks,
> >Kevin Donn
> >
> >--- In, "kgdonn" <kd.ibo@M...> wrote:
> > >
> > > It seems either I or IBO is missing something fundamentally
> > > important. I'm doing an Insert, Post, Edit, & Post on a
> >TIBOTable,
> > > and I get "Record was not located to update". What gives?
> > >
> > > Here's the code:
> > >
> > > procedure TForm1.InsEditBtnClick(Sender: TObject);
> > > begin
> > > with TIBOTable.Create(nil) do try
> > > TableName:='LEA';
> > > IB_Connection:=IBODatabase1;
> > > Open;
> > > Insert;
> > > Fields[0].AsInteger:=5000;
> > > Post;
> > > Edit;
> > > Fields[1].AsString:='Donn';
> > > Post
> > > finally Free end
> > > end;
> Unless you changed from the default, ibodatabase's transaction is
> Autocommit. The first Post both posts and commits the insert.
The default
> CommitAction of ibotable is caInvalidateCursor, which basically
means the
> cursor is "nowhere" after a commit. Hence, the second Post has no
> from which to populate the WHERE clause it creates for the UPDATE
> Can you do it? yes. Study the help for TIB_CommitAction to see
> behaviour you want after the Commit - in theory, caRefreshKeys
should be
> enough, since there is no data in the inserted row except for the
> key (which, one hopes, you have set as the Keylink).
> However, when the keys are refreshed, the buffer pointer won't be
on the
> row you inserted, since it's at the very end of the table. You
could try
> creating a bookmark for the row before you call post and then
> GoToBookmark afterwards, before you call Edit.
> Alternatively, setting BufferSynchroFlags := [bsAfterInsert] as
part of
> your Create sequence might be enough to do the trick.
> Now some uninvited comments.
> Doing this sort of stuff in a table component is costly. You'll
> that native IBO doesn't even have a table component. This is by
> design. With Fb/IB there is no physical structure on disk that is
> on directly, as there is with Paradox, Access, etc. (which the
VCL's TTable
> was designed for). This model is therefore hopeless for a
> DMBS If the table is bigger than about 200 rows. The traffic on
the wire
> for keeping a table component's buffers in synch with database
state is
> horrendous, even if you weren't using Autocommit and forcing
either the
> whole table (caRefresh) or a set consisting of the PK of every row
in the
> table (caRefreshKeys) to pass across the wire every time the user
> the Save button.
> From an application design POV, it doesn't make sense, either.
Why would
> you want to create a row, commit it and then immediately update
it? Why
> not apply the non-key data directly in the Insert statement? The
> here is that you create a row with no data. It now exists and the
only way
> to "undo" it will be to delete it. So, supposing that the data
you apply
> in the Edit throws an exception, you have this empty row sitting
in the
> database with no context. This is essentially the effect of the
> application designer forcing tasks to be non-atomic.
> And then, if you decide to take control of the transaction
yourself and
> take the care needed to make user tasks atomic, you bump into the
> of proliferating record versions on the server. Inserting and
> updating (or, perhaps, more pertinently, deleting) the same row
inside the
> same transaction is (currently) allowed. In the multi-
> architecture (MGA), multiple operations on the same row within the
> transaction create multiple versions of the that row, which can
> aggravate problems associated with garbage collection. It is so
contrary to
> recommended practice that it has been made illegal in Firebird 2.
> Helen