Re: New feature: accumulative functions. - Mailing list pgsql-general

From David Johnston
Subject Re: New feature: accumulative functions.
Date
Msg-id CAAB7D45-B119-488B-8A6C-E97C3B1E9101@yahoo.com
Whole thread Raw
In response to New feature: accumulative functions.  (pasman pasmański <pasman.p@gmail.com>)
List pgsql-general
On Sep 25, 2011, at 9:19, pasman pasmański <pasman.p@gmail.com> wrote:

> Hi.
>
> I propose to add "accumulative" flag to a function definition. This
> flag would be set for function f(x) which is accumulative and
> immutable.
>
> This flag allows to use an index on  x for clauses containing f(x):
>
> where f(x) = const
> where f(x) > const
>
> and so on.
>
>

We can term it a Schrodinger function :)

I don't understand how it can have mutable state (accumulator) and still be called immutable.

Can explain further and give an example (or better yet, real life) use-case?

David J.

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