Greenplum Database uses a cost-based query planner that relies on database statistics. Accurate statistics allow the query planner to better estimate selectivity and the number of rows that a query operation retrieves. These estimates help it choose the most efficient query plan. The ANALYZE command collects column-level statistics for the query planner.
You can run both VACUUM and ANALYZE operations in the same command. For example:
=# VACUUM ANALYZE sales_data;