From a Vertica query plan: explain select country, count(*) from tablename group by 1 ... +-GROUPBY PIPELINED (GLOBAL RESEGMENT GROUPS) [Cost: 79,

From a Vertica query plan: explain select country, count(*) from tablename group by 1 ... +-GROUPBY PIPELINED (GLOBAL RESEGMENT GROUPS) [Cost: 79, Rows: 1] (PATH ID: 1) | Aggregates: count(*) | Group By: tablename.country | Execute on: All Nodes | +---> STORAGE ACCESS for tablename [Cost: 78, Rows: 14M (1 RLE)] (PATH ID: 2) ... Note the row count at the top level. This type of thing only works when the group column is the first in the projection sort order (or for multiple columns, a prefix of it). Generally GROUPBY PIPELINED indicates that the sort order is being used (including RLE).