110 CHAPTER 6 Shared-nothing Partitioning
collocated, the shaded section of data for table A on each node will join with the shaded
section of data in table B. However, in a worst-case scenario the entire join data for one
of the tables will need to be transferred to the other’s nodes for joining.
This represents a very interesting and challenging design goal of trying to find par-
titioning keys that achieve good collocation while still providing even data distribution
across the nodes.
You can be certain that tables are collocated if they have the same number of col-
umns in the partitioning key, and if the data types of the corresponding columns are
node compatible. Rows in collocated tables with the same partitioning key value are
always placed ...