Database Reference
In-Depth Information
Figure 7.5
ASOsamp.Sample database properties: Statistics. (From Oracle Essbase Administration Services.
With permission.)
ones because the input-level cell is uniquely identified in its own right and as a descen-
dant of its ancestors. The structure of this bitmap can be seen on the “Statistics” tab in
the “Database Properties” dialog in Essbase Administration Services (EAS) (Figure 7.5).
The fact that the
bitmap identifies each level-0 member directly, without wander-
ing through the hierarchy, is the key to understanding ASO
. As a simple example of
this direct identity, consider a cube for my family: A query would find me as one of the
descendants of my grandfather nathan Pressman without having to check the geneal-
ogy contained in the outline that indicates I am the son of Abraham Pressman who is,
in turn, the son of nathan.
The role of the sorting-needle is played by a bitmap “mask” that the query engine
generates when it translates your query for execution. This mask indicates where there
must be a 0 (zero) and where there must be a 1 and can also in some implementations
indicate where it could be either, resulting in a bit string that might look something like
00000100??????1010?????????. A query then becomes a simple matter of comparing this
mask to the bitmap attached to each input-level cell. As I will show, the bit code attached
to each input-level cell is not just a simple hole or punch (bit) for each member, but is
instead a multibit code that identifies not only the member name to which the card data
applies (let us say their current age), but also a series of bits that allows my card to be
identified as belonging to me or to a descendant of my father or to a descendant of my
grandfather, all of which I (hopefully) am.
