Re: Dynamic PL/pgSQL select query: value association propblem

Thanks for answering.

Zitat von Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>:

> Why you don't create query like
>
> EXECUTE 'SELECT xxx FROM TAB WHERE A = $1.x AND B = $1.y' USING NEW;

I shall try. This would be the direct way, but I doubt the placeholder
$1 can be a record.

> I don't understand tou your case, but usually count(*) > 0 looks like
> antipattern - probably you want to use EXISTS(...)

It is about SCD2
(https://en.wikipedia.org/wiki/Slowly_changing_dimension#Type_2:_add_new_row)
and new versions of business key pay load. I want to avoid bloating
the table by useless because still valid/active business key pay load
versions, so I want to check beforehand whether I need to
invalidate/deactivate the valid/active record for the given business
key. Example
Table T with columns A (number), B (text), K (text, business key),
VF(date), VU (date)
content record 1: A=1, B='old', K='key1', vf=yesterday, vu={null}
If I insert (1, 'old', 'key1') I do *not* need to invalidate record 1
as there is no gain of information (identical values for A and B). If
I still do, I bloat the table with a useless business key pay load
version. (What an awkward expression I invented there but record
version is not cleat enough in my opinion.)
If I insert (1, 'new', 'key1') I must invalidate record 1 by updating
VU to today. Otherwise I have overlapping validity.
If I insert (1, 'new', 'key2') I do *not* need to invalidate a record
because key2 is not yet in the table. If I still update, it is just
heating the atmosphere with CPU power for nothing.

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