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When creating a comprehensive design, Database Designer creates projections based on data statistics and queries. It also reviews the submitted design tables to decide whether projections should be segmented (distributed across the cluster nodes) or replicated (duplicated on all cluster nodes).
For detailed information, see the following sections:
Replication occurs when Vertica stores identical copies of data across all the nodes in your cluster.
Assuming that largest-row-count equals the number of rows in the design table with the largest number of rows, Database Designer recommends that a projection be replicated if any of the following conditions is true:
largest-row-count < 1,000,000 and number of rows in the table <= 10% of largest-row-count
largest-row-count >= 10,000,000 and number of rows in the table <= 1% of largest-row-count
The number of rows in the table <= 100,000
For more information about replication, see High availability with projections.
Segmentation occurs when Vertica distributes data evenly across multiple database nodes so that all nodes participate in query execution. Projection segmentation provides high availability and recovery, and optimizes query execution.
When running Database Designer programmatically or using Management Console, you can specify to allow Database Designer to recommend unsegmented projections in the design. If you do not specify this, Database Designer recommends only segmented projections.
Database Designer recommends segmented superprojections for large tables when deploying to multiple node clusters, and recommends replicated superprojections for smaller tables.
Database Designer does not segment projections on:
Single-node clusters
LONG VARCHAR and LONG VARBINARY columns
For more information about segmentation, see High availability with projections.