PostgreSQL version:


Sets the planner's estimate of the cost of a disk page fetch that is part of a series of sequential fetches. The default is 1.0. This value can be overridden for tables and indexes in a particular tablespace by setting the tablespace parameter of the same name (see sql-altertablespace).


The main reason to modify seq_page_cost is to try to get planner costs to more-or-less indicate execution times in milleseconds. All other costs change relative to this cost automatically.