From: Mitar <mmitar@gmail.com>
> On Thu, Dec 20, 2018 at 12:07 PM Rob Sargent <robjsargent@gmail.com> wrote:
> > Are you hoping to see the difference in the returned values for successive calls to the same query?
>
> i would like to in as close to real-time as possible get notification when results of a query would have changed if I
woulddo the same query again, without me having to do polling or without me having to do diffing.
Hmm, I guess I could see that as long as the DB wasn't too [write] busy, else you'd be flooded with notifications.
Some years ago when I was working on a web app in Perl (which uses the DBI module for all communication to the DB), I
subclassedDBI in order to see all calls to the DB. For most statements, I just let all the calls go thru. But for
inserts,I wrote to a file the data that was being inserted; for deletes I wrote what was being deleted; and for updates
Iwrote the before and after values. (For the last 2 I changed the delete/update into a select to get the data.) It made
itmuch easier to see how data changed -- especially when I was new to the app.
You could do something like that, where you have an interceptor that reports on data changes, filtering/searching for
justthe parts you want as you see fit. Of course, that would be just for your app, it wouldn't catch changes made from
psqland other tools.
Maybe it's a useful idea for you ... or maybe not. 😊
If you had to have all statements no matter what tool was used to change data, I'd probably change log_statements to
"all","tail -f" the Pg log, and "do the right thing" (which could be non-trivial).
Kevin
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