Re: Logical problem with transactions and GUI-clients

Andreas,

You need to look at the documentaton on Concurrency Control. This will answer
all your questions. On my machine it is mvcc.html. It is also on the Postgres
web site.

Basically, we do not start any transactions on the client side except for one
complex operation that demands backing out multiple layers of updates on
failure of any one part of the process.

On Tuesday 31 May 2005 01:25 pm, Andreas saith:
> Hi,
>
> I do understand the reasons to use transactions and what they do.
> My problem is the actual usage of transactions in a complex client
> application.
>
> Suppose there are tables:
> customers (cus_id, name, notes, ...)
> postal_adresses (pa_id, cust_id, street, zip, city, county)
> electronic_addresses (ea_id, cust_id, e_adress, es_type)
> // ea_type might be email, phone-, fax-number, www, ...
> contacts (cust_id, contact_date, notes, ...)
> ... and some more that are foreign-keyd to customers
>
> users create and edit those records in forms.
>
> Where would I start the transaction?
>
> 1) On start of the application
> A crash would trigger a rollback and kill every bit of work a user had
> done probaply on the whole workday.
> NOT GOOD
>
> 2) On opening the customer form.
> Then anything that is done gets lost, when the transaction doesnt get
> committed for some reasons on close of the customer-form.
> This was sensible if the customer is new.
> But let's say a user opens customer 42 and calls him up on the phone.
> For this call the user appends a contact to make notes about the
> conversation. ---> Contact-Form
> The customer gave a new postal-adress. ---> PAddress-Form
> Child-forms are closed and the user is back in the Customer-Form which
> lay open while we had the detail-forms on top of it.
> Then lightning strikes ---> CRASH so the Customer-Form didn't get
> committed. The new contact and address is lost. The users wouldn't expect
> nor like this behaviour either.
>
> 3) On opening of every Child-Form.
> There might be an committed address even though the customer got rolled
> back.
> This would violate a referential integrity constraint.
>
>
> Can someone point me the way to go, please ?
>
>
>
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