aggregate-projection-types.md
Vertica provides several types of projections for storing data that is returned from aggregate functions or expressions:
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Live aggregate projection: Projection that contains columns with values that are aggregated from columns in its anchor table. You can also define live aggregate projections that include user-defined transform functions.
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Top-K projection: Type of live aggregate projection that returns the top
k
rows from a partition of selected rows. Create a Top-K projection that satisfies the criteria for a Top-K query. -
Projection that pre-aggregates UDTF results: Live aggregate projection that invokes user-defined transform functions (UDTFs). To minimize overhead when you query those projections of this type, Vertica processes the UDTF functions in the background and stores their results on disk.
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Projection that contains expressions: Projection with columns whose values are calculated from anchor table columns.