how-columns-are-ranked.md

Vertica stores columns included in the projection sort order on the fastest available storage locations. Columns not included in the projection sort order are stored on slower disks. Columns for each projection are ranked as follows:

  • Columns in the sort order are given the highest priority (numbers > 1000).

  • The last column in the sort order is given the rank number 1001.

  • The next-to-last column in the sort order is given the rank number 1002, and so on until the first column in the sort order is given 1000 + # of sort columns.

  • The remaining columns are given numbers from 1000–1, starting with 1000 and decrementing by one per column.

Vertica then stores columns on disk from the highest ranking to the lowest ranking. It places highest-ranking columns on the fastest disks and the lowest-ranking columns on the slowest disks.