Physical Schema

Unlike traditional databases that store data in tables, Vertica physically stores table data in projections, which are collections of table columns. Projections store data in a format that optimizes query execution. Like materialized views, projections store result sets on disk rather than compute them each time they are used in a query. Vertica automatically refreshes these result sets with updated or new data.

Projections provide the following benefits:

• Compress and encode data to reduce storage space. Vertica also operates on the encoded data representation whenever possible to avoid the cost of decoding. This combination of compression and encoding optimizes disk space while maximizing query performance.
• Facilitate distribution across the database cluster. Depending on their size, projections can be segmented or replicated across cluster nodes. For instance, projections for large tables can be segmented and distributed across all nodes. Unsegmented projections for small tables can be replicated across all nodes.
• Transparent to end-users. The Vertica query optimizer automatically picks the best projection to execute a given query.
• Provide high availability and recovery. Vertica duplicates table columns on at least K+1 nodes in the cluster. If one machine fails in a K-Safe environment, the database continues to operate using replicated data on the remaining nodes. When the node resumes normal operation, it automatically queries other nodes to recovers data and lost objects. For more information, see High Availability with Fault Groups and High Availability With Projections.