Next beta will have record locks.

[Ruslan Zasukhin]

on 7/2/03 11:52, erne at ernestogiannotta at tiscalinet.it wrote:

>> As I see you going to use this mode in your app as the main way.
>> May be you need rethink your design? :-)
>> 
> 
> I'll give you a real life example:
> I've a browse window resulting from a complex join query and thus not
> writeable (that's why I asked you writable join cursors)
> User double clicks a cell to edit it
> I keep reference to the recid and table of each column in the cursor so I
> build a single table editable cursor with the field needed and let the user
> edit it, then I issue Update and the data is changed in real time into my
> browse window (BTW I could use a SQLExecute to achieve the same, what about
> this attempting to modify Locked records?)

Erne, this is NOT how works big mature RDBMS as far as I know.
Only Access have cursor which mirrow changes.

You can easy see why it is not possible, if you note, that multi-table join
many RDBMS build as other tmp table. So your Update change original table,
but this do not affect your tmp table of join cursor.


> Now with the Locked cursor I'd have to destroy the cursor used by the browse
> window, perform the update then rebuild the cursor

Yes, this is how works big RDBMS that assume that system can have a lots of
users connected.

Access that allow such runtime update of cursor is NOT intended for use in
big groups of users.  This is why they can allow self this behavior.

Well, assuming that Valentina is used for both local db development and
remote db I think we really should support both ways. And this is
responsibility of Valentina Developer use tools correctly.

> There's lots of situations like this, I often have cursors living around and
> used to be happy with it... actually it is one of the Valentina features I
> love most

And this feature will get a lots of criticism from Developers used to Oracle
and Sybase. 

By transaction rule:
    actions of one user should not be visible to other users until he
    commit transaction...

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I have hear that SQL Server allow modify some columns of multi-table JOIN
cursor, but only columns that belong to Table 'MANY'.
I agree with this, and with sure this also will be added to Valentina ...
Although then we must be able ask each column if it can be modified.
 
Example: JOIN of    Person and Phone tables
                         1   :  M

You get cursor where e.g. name 'Erne' repeated 5 times with different
phones. Sql Server allow you in this cursor update phone number, i.e. Fields
from MANY table. But we cannot update in one record name 'erne', because
then we break consistency -- rest 4 records still will have 'Erne'

So I wonder, if such RULE will satisfy your task?
Do you change in your app only MANY table columns ?


-- 
Best regards,
Ruslan Zasukhin      [ I feel the need...the need for speed ]
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e-mail: ruslan at paradigmasoft.com
web: http://www.paradigmasoft.com

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