Parameter type: Floating point
Default value: 1
Range: 0 to 1.79769e+308
Minimum scope of effect: Per session
When value changes take effect: Immediate
Required authorization to activate: Session user
Sets the planner's estimate of the cost of a disk page fetch that's part of a series of sequential fetches. You can override this value for a particular tablespace by setting the tablespace parameter of the same name. See
ALTER TABLESPACE in the PostgreSQL core documentation.
The default value assumes very little caching, so it's often a good idea to reduce it. Even if your database is significantly larger than physical memory, you might want to try setting this parameter to something lower than the default value of 1 to see if you get better query plans that way. If your database fits entirely in memory, you can lower this value much more, for example, to 0.1.