Posted by Jerry Stuckle on 05/19/06 20:42

rich wrote:
> I am building an app using php and postgresql. My questionis this.
> How do you handle people wanting to make parallel changes to a record.
> Since in web apps you are doing a select, bring over a record then
> updating it, there is no lock on that record while you are making the
> changes in your browser window. Does transactions handle that? Do you
> make your selection and update all part of the same transaction? This
> whole scenario has me stumped.
>

Keep the original values. Before updating, read the record in again and compare
the values to the old ones. If they don't match, put the window back up with
the new values and tell the user.

You can also be a little more creative. Check the columns which are being
updated. If they haven't changed (but perhaps others have), go ahead and allow
the update to the changed columns. However, if one or more columns have been
changed, send a message back to the user with the new values from the database.

A lot of hassle, I know. However, you wouldn't want to lock the row anyway.
What happens if someone displays the record then closes his browser? Now you
have a locked recored which you can't unlock (until perhaps some timeout value
expires).

--
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Jerry Stuckle
JDS Computer Training Corp.
jstucklex@attglobal.net
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