Anchor Projection

An anchor table is a database table that is the source for data in a projection. All projections have anchor tables. The projections are the physical storage of the table data. When you drop an anchor table and specify the CASCADE keyword, HP Vertica drops the anchor projection and the anchor table.

An anchor projection is the physical storage for an anchor table that has a live aggregate projection. You must create an anchor projection before you create a live aggregate projection, including Top-K projections. The anchor projection segmentation must be a subset of the live aggregate projection.

When HP Vertica loads data into an existing anchor table, it appends the data to the anchor projection. Then it aggregates the data and adds it to the live aggregate projection. After you create a live aggregate or Top-K projection, you cannot perform any update, delete, or merge operations on the anchor table or anchor projection.

When you drop the anchor table and specify the CASCADE keyword, HP Vertica drops the anchor table, the anchor projection, and the live aggregate projection.