Re: Views of views, complexity and speed.

bombadil(at)wanadoo(dot)es wrote:
> El martes 05 de febrero, Jan Wieck escribió:
> > The question I have is what do you really compare? You said
> > "looking in plain tables instead of other views". Does that
> > mean your query is faster when you build one big view against
> > all the base tables instead of cascaded views, or what? What
> > is the performance difference if you instead of using the
> > cascaded views query all the base tables in a big join
> > directly?
>
> Your comment resumes very well my essential question. I only want to
> know if there is a reason for thinkink that a cascade of views can be
> slower than a complex view that includes all tables. Is the planner
> well tuned for working with this complex cases (cascade of views)?
>
> Actually I am making experiments with all this stuff. Better idea
> than sending a lazy question in the list.

In principle the penalty for cascading views should be
negligible, because the resulting queryplan after rewriting
ought to be comparable to what you would have to write as
query yourself, if you wouldn't have views at all. So after
some recursion in the rewriter, the planner and optimizer
should face the same join problem.

As long as your not gonna write triggers to maintain the
information you want from the views in plain tables, the
answer is that there is no significant performance
difference.

Jan

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