The Physical Schema (Projections)
A physical schema consists of a set of projections used to store data on disk. The projections in the physical schema are based on the objects in the Logical Schema.
A projection is a special case of a 
materialized view that provides physical storage for data. A projection can contain some or all of the columns of one or more tables. A projection that contains all of the columns of a table is called a superprojection. A projection that joins one or more tables is called a pre-join projection. Most projections are used for ad-hoc query processing and K-safety but it is possible to have query-specific projections.
A superprojection is a projection that contains every column of a table in the Logical Schema. A table can have multiple superprojections with different sort orders.
A materialized view is similar to a standard SQL view with one major exception: the data is actually stored on disk rather than computed each time the view is used in a query. A materialized view, then, must be refreshed whenever the data in the underlying tables is changed. A projection is a special case of a materialized view.
This section is primarily about using the Database Designer to create a physical schema design: a set of projections that provides K-Safety.
K represents the maximum number of nodes in a database that can fail and recover with no loss of data. In Vertica V2.1, the value of K can be zero (0) or one (1). The value of K can be one (1) only when the Physical Schema design meets certain requirements. The designs generated by the Database Designer are K-Safe.
A physical schema consists of a set of projections used to store data on disk. The projections in the physical schema are based on the objects in the Logical Schema.
The Database Designer is a tool that analyzes a logical schema definition, sample queries, and sample data and generates a set of projections in the form of an SQL script to be executed after you create the tables but before you load any data. The script creates a minimal set of superprojections to ensure K-Safety, and optionally pre-join projections. In most cases, the projections created by the Database Designer provide excellent query performance within physical constraints. You can, however, write a custom projection script should the Database Designer not meet your needs.
A superprojection is a projection that contains every column of a table in the Logical Schema. A table can have multiple superprojections with different sort orders.
