A facility for populating a segment from a population of individuals is described. The facility accesses two or more fact tables, each containing data about attributes of a number of users who are members of a number of arbitrary user groups. The facility generates a number of column chunks from each fact table. Each column chunk contains data about a single attribute of users that are members of a single arbitrary user group. The facility applies a segment membership test that tests particular user attributes to each arbitrary user groups in turn. In doing so, the facility collects the generated column chunks that contain data about attributes of users that are members of the current arbitrary user group tested by the segment membership test. The facility applies the segment membership test to the collected column chunks to identify individuals within the arbitrary user group that satisfy the segment membership test.