On Tue, Jan 24, 2017 at 4:32 AM, Peter Moser <pitiz29a@gmail.com> wrote:
> NORMALIZE: splits all the ranges of one relation according to all the range
> boundaries of another (but possibly the same) relation whenever some equality
> condition over some given attributes is satisfied.
>
> When the two relations are the same, all ranges with the given equal attributes
> are either equal or disjoint. After this, the traditional GROUP BY or DISTINCT
> can be applied. The attributes given to NORMALIZE for a (temporal) GROUP BY are
> the grouping attributes and for a (temporal) DISTINCT the target list
> attributes.
>
> When the two relations are different, but they each contain disjoint ranges
> for the same attributes (as the current limitation for the set operations is)
> we perform a symmetric NORMALIZE on each of them. Then we have a similar
> situation as before, i.e., in both relations ranges with the same attributes
> are either equal or disjoint and a traditional set operation
> (EXCEPT/INTERSECT/UNION) can be applied. The attributes given to NORMALIZE for
> a (temporal) EXCEPT/INTERSECT/UNION are the target list attributes.
>
>
> ALIGN: splits all the ranges of one relation according to all the range
> intersections of another relation, i.e., it produces all intersections and
> non-overlapping parts, whenever some condition is satisfied.
>
> We perform a symmetric ALIGN on each relation, after which a traditional inner
> or outer join can be applied using equality on the ranges to calculate the
> overlap. The condition given to a (temporal) inner or outer join is the
> join condition without overlap.
I don't quite understand the difference between NORMALIZE and ALIGN.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company