ERIC Lawson - x52010 wrote:
>
> Hi, and TIA,
>
> Can anybody here answer these questions:
>
> 1) I've seen references to the maximum size of a tuple as being
> configurable within the range of 8 to 32K, yet the incorporation of blobs
> seems to contradict any maximum size constraint. Is there a maximum tuple
> size, and if so, what is it? (To be sure, the server environment limits
> the size of a tuple, attribute and class, but does postgreSQL imposes
> limits itself?)
A bit less than 8k is the 'default' limit (8k less tuple overhead). You
can use the 'LZTEXT' type to compress large text fields though, as a
first approach. You can recompile PostgreSQL with the block size set
larger (up to 32k) so the limit increases to a bit less than 32k.
Coming in version 7.1 is a thing called 'TOAST' (it's in current CVS)
which will let you store larger tuples - have a read about it on the
website.
> 2) I'd like to use a plpgsql procedure to send mail when a trigger event
> or condition pertains (e.g., when the interval between the system date and
> a date stored in an attribute reaches 14 days). Is this possible with
> plpgsql, and how would it be achieved?
A PL/PGSQL procedure won't run by itself. You would have to set
something up to do a pass through the database looking for such records
periodically.
SELECT * FROM tbl WHERE tbl.c_time < (now() - timespan('14 days'));
would be a suitable SQL query. If the c_time field is indexed it would
use an indexed lookup and so should be efficient.
You could run such a query in a shell script like:
IDLIST=`psql -d database -c "SELECT my_id FROM tbl WHERE tbl.c_time <
(now() - timespan('14 days'));"`
for ID in $IDLIST
do
echo "$ID expired" | mail -s "$ID expired" user@email.dom
done
If you're doing much more complex stuff than that I'd go for a
higher-level language for the scripting such as Perl, Python or C.
Hope this is some assistance,
Andrew.
--
_____________________________________________________________________
Andrew McMillan, e-mail: Andrew@cat-it.co.nz
Catalyst IT Ltd, PO Box 10-225, Level 22, 105 The Terrace, Wellington
Me: +64 (21) 635 694, Fax: +64 (4) 499 5596, Office: +64 (4) 499 2267
