Re: New feature: accumulative functions.

My english is not perfect, by accumulative i think about monotonically
increasing function.

It works that for clause WHERE f(x)=const:
1. Read root page of index_on_x and get x1 ... Xn
2. Calculate f(x1) ... f(xn) for this page
3. When f(x1)<=const<= f(xn) then x1 <= searched x <= xn and we can
test smaller range (xlower, xgreater).
4. Otherwise no rows satisfy condition.

Step 3 we repeat for current index's page and subpages until xlower =
searched x = xgreater

2011/9/25, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
> =?ISO-8859-2?Q?pasman_pasma=F1ski?= <pasman(dot)p(at)gmail(dot)com> writes:
>> I propose to add "accumulative" flag to a function definition. This
>> flag would be set for function f(x) which is accumulative and
>> immutable.
>
> Maybe you'd better define what you mean by "accumulative" ...
>
>> This flag allows to use an index on x for clauses containing f(x):
>> where f(x) = const
>> where f(x) > const
>
> ... because it's sure not clear how you would get that to work.
>
> regards, tom lane
>

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pasman