Re: column max length / max timestamps from system tables

1) you can create an aggregate table, and save the relevant aggregates as
per your requirement.
then you can have triggers, insert/update to check if the new agg is
greater than ones in aggregate table, update that table else keep it
unchanged.
when delete, delete the row from the agg table if the deleted row values
equal to the agg values. the agg table is now empty.

then create a function to query the agg table to return relevant values, if
not found, query the aggregates from the base table, update the agg table
and then return those values.
that way, unless you delete the row containing the max value, you should be
able to get agg values pretty quickly.
but it would slow down DMLs by a small amount of time.

On Thu, 3 Jun 2021 at 01:31, <dave(at)davebolt(dot)co(dot)uk> wrote:

> I don’t have suitable data to hand to test, but I would expect finding the
> max on a timestamp column would be PDQ, especially if it is an indexed
> column.
>
> For the other column I’m guessing more work has to be done finding the
> length for each row. Maybe maintaining a column containing the current
> length for each row would help?
>
> Anyway, can you test the max timestamp and the max col length separately
> to confirm where the time goes?
>
> Re-reading the original question makes me think there may be more
> complexity to your querie(s) then I realise.
>
> Dave
>
>
>
> *From:* sbob [mailto:sbob(at)quadratum-braccas(dot)com]
> *Sent:* 02 June 2021 20:18
> *To:* David G. Johnston
> *Cc:* Pgsql-admin
> *Subject:* Re: column max length / max timestamps from system tables
>
>
>
> Unfortunately this takes hours since the table has > 500million rows
>
> just wanted to see if there was a shorrtcut / alternate
>
>
>
> On 6/2/21 11:13 AM, David G. Johnston wrote:
>
>
>
> On Wed, Jun 2, 2021, 10:05 sbob <sbob(at)quadratum-braccas(dot)com> wrote:
>
> Hi all;
>
>
> we need to pull the max timestamp for a set of columns and the max
> string length for another set of columns. Can I get this from system
> tables? If so, how up to date would it be?
>
>
>
> No. Just query the table directly.
>
>
>
> David J.
>
>
>
>
>
>

--
Thanks,
Vijay
Mumbai, India