Обсуждение: Knowing new item in table...
im still in the dark when it comes to postgres..... is there a way i can know if there was a new entry on a table... scenario... i have a script that runs every 5 minutes... that script checks if there's a new entry in that table... and if YES there's a new entry ill do some processing... is there an internal utility that i can use in postgres that can tell me that this rows a new commers... hehehe.... if someone has other ideas on how to deal with this speak out... thanks in advance...... btw.. my idea is that that table will have an addtional column as reference lets say column "READ" 1 for yes 0 for NO
The best way to do this is probably have an auto-increment field in your table. When your script runs it checks and stores the highest value in that auto-increment field and compares with the value it had the previous time it was run. It then returns all records greater than the previous value of the auto-increment field. regards -- Jason Wong Gremlins Associates ----- Original Message ----- From: macky <macky@edsamail.com> To: <pgsql-sql@postgresql.org>; <pgsql-novice@postgresql.org> Sent: Friday, August 03, 2001 4:26 PM Subject: [NOVICE] Knowing new item in table... > im still in the dark when it comes to postgres..... is there a way i can > know if there was a new entry on a table... > > scenario... > > i have a script that runs every 5 minutes... that script checks if there's > a new entry in that table... and if YES there's a new entry ill do some > processing... > > > is there an internal utility that i can use in postgres that can tell me > that this rows a new commers... hehehe.... > > > if someone has other ideas on how to deal with this speak out... > > thanks in advance...... > > btw.. > my idea is that that table will have an addtional column as reference > lets say column "READ" 1 for yes 0 for NO > > > > > > ---------------------------(end of broadcast)--------------------------- > TIP 3: if posting/reading through Usenet, please send an appropriate > subscribe-nomail command to majordomo@postgresql.org so that your > message can get through to the mailing list cleanly >
macky wrote: > im still in the dark when it comes to postgres..... is there a way i can > know if there was a new entry on a table... > > scenario... > > i have a script that runs every 5 minutes... that script checks if there's > a new entry in that table... and if YES there's a new entry ill do some > processing... > > is there an internal utility that i can use in postgres that can tell me > that this rows a new commers... hehehe.... > > if someone has other ideas on how to deal with this speak out... > > thanks in advance...... > > btw.. > my idea is that that table will have an addtional column as reference > lets say column "READ" 1 for yes 0 for NO You could have a timestamp field with a default value of 'now' defined, and have your script select all records from the table with a time after 5 minutes ago. Bryan
what kind of processing are you doing in the script? is there a reason why you are not using a trigger or rule on the table that is executed straight away when a new row is added? tamsin > -----Original Message----- > From: pgsql-novice-owner@postgresql.org > [mailto:pgsql-novice-owner@postgresql.org]On Behalf Of macky > Sent: 03 August 2001 09:26 > To: pgsql-sql@postgresql.org; pgsql-novice@postgresql.org > Subject: [NOVICE] Knowing new item in table... > > > im still in the dark when it comes to postgres..... is there a way i can > know if there was a new entry on a table... > > scenario... > > i have a script that runs every 5 minutes... that script checks > if there's > a new entry in that table... and if YES there's a new entry ill do some > processing... > > > is there an internal utility that i can use in postgres that can tell me > that this rows a new commers... hehehe.... > > > if someone has other ideas on how to deal with this speak out... > > thanks in advance...... > > btw.. > my idea is that that table will have an addtional column as reference > lets say column "READ" 1 for yes 0 for NO > > > > > > ---------------------------(end of broadcast)--------------------------- > TIP 3: if posting/reading through Usenet, please send an appropriate > subscribe-nomail command to majordomo@postgresql.org so that your > message can get through to the mailing list cleanly >
On Friday 03 August 2001 09:26, macky wrote: > im still in the dark when it comes to postgres..... is there a way i can > know if there was a new entry on a table... > > scenario... > > i have a script that runs every 5 minutes... that script checks if > there's a new entry in that table... and if YES there's a new entry ill do > some processing... Isn't this a perfect example of when a notification and listen setup would be helpful (assuming that a trigger isn't acceptable)? -Ken
--- macky <macky@edsamail.com> wrote:
> im still in the dark when it comes to postgres.....
> is there a way i can
> know if there was a new entry on a table...
That's a pretty common problem.
> scenario...
>
> i have a script that runs every 5 minutes... that
> script checks if there's
> a new entry in that table... and if YES there's a
> new entry ill do some
> processing...
Probably the most straightforward thing to do is to
simply insert a timestamp in each row as it is added
to the database. That way you can do a simple select
to figure out which rows have been added:
SELECT * FROM my_table WHERE insert_time > now() - '5
minutes'::interval
or alternatively
SELECT * FROM my_table WHERE insert_time > '2001-08-03
11:30'
The best part is that creating a column that includes
a timestamp automagically is fairly easy to do.
Simply define your table like this:
CREATE TABLE foo (
insert_time timestamp DEFAULT CURRENT_TIMESTAMP,
name text
);
Once your table is created you simply insert into
table foo ignoring the insert_time column like so:
INSERT INTO foo (name) VALUES ('Jason');
and your timestamp automagically gets inserted:
processdata=> SELECT * FROM foo;
insert_time | name
------------------------+-------
2001-08-03 11:32:48-06 | Jason
(1 row)
Pretty neat, huh?
> is there an internal utility that i can use in
> postgres that can tell me
> that this rows a new commers... hehehe....
Nope, you have to come up with the logic yourself.
However, PostgreSQL has all kinds of tools that are
really helpful.
> if someone has other ideas on how to deal with this
> speak out...
>
> thanks in advance......
>
> btw..
> my idea is that that table will have an addtional
> column as reference
> lets say column "READ" 1 for yes 0 for NO
>
That would work too, but it would be a lot harder.
For example, you would have to first select all the
rows where READ is 0, do your processing, and then
update all of those rows to 1. You would almost
certainly want to do all of this in a transaction so
that you could roll READ back to 0 if something went
wrong, and you would probably want to lock the table
to boot as you would have to worry about your
processing step taking more than 5 minutes. If it
did, the second transaction would see the last 10
minutes of of inserts as being unread even though the
first transaction was still working on them.
I hope this is helpful,
Jason
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> > > --- macky <macky@edsamail.com> wrote: > > im still in the dark when it comes to postgres..... > > is there a way i can > > know if there was a new entry on a table... > > That's a pretty common problem. > create trigger upd_table before insert table for each row execute -- Danny Aldham Providing Certified Internetworking Solutions to Business www.postino.com E-Mail, Web Servers, Web Databases, SQL PHP & Perl