Re: Including Snapshot Info with Indexes
От | Csaba Nagy |
---|---|
Тема | Re: Including Snapshot Info with Indexes |
Дата | |
Msg-id | 1191918828.16320.33.camel@PCD12478 обсуждение исходный текст |
Ответ на | Re: Including Snapshot Info with Indexes ("Gokulakannan Somasundaram" <gokul007@gmail.com>) |
Ответы |
Re: Including Snapshot Info with Indexes
Re: Including Snapshot Info with Indexes |
Список | pgsql-hackers |
[snip] > In the case of User-Defined functions, the user should be defining it > as Deterministic. The user CAN already define his functions as "Deterministic=IMMUTABLE"... the problem is that many of us will define functions as immutable, when in fact they are not. And do that by mistake... and there's nothing postgres can do about that. > Can we frame a set of guidelines, or may be some test procedure, which > can declare a certain function as deterministic? You mean postgres should check your function if it is really immutable ? I can't imagine any way to do it correctly in reasonable time :-) Imagine a function of 10 parameters which returns the sum of the parameters all the time except for parameters all 1 it will randomly return a value _once in a thousand executions_... please find a generic algorithm which spots this function as not immutable in reasonable execution time ;-) So this example is a bit extreme, but don't underestimate the user ;-) > I am just saying from the top of my mind. Even otherwise, if we can > even restrict this indexing to only Built-in deterministic functions., > don't you think it would help the cause of a majority? I have just > made the proposal to create the index with snapshot a optional one. Restrictions like this are always confusing for the end user (i.e. why can I use built-ins here and not my own ?). I leave to the actual coders to say anything about code maintenance concerns... Cheers, Csaba.
В списке pgsql-hackers по дате отправления: