Now that all of the ways a query executes have been covered, some of the more obscure query-planning parameters can be explained usefully.
Other query-planning parameters
effective_cache_size
Defaulting to 128 MB, effective_cache_size is used to represent approximately how much total disk space is available for caching the database. This is normally set to the total of shared_buffers plus the size of the operating system disk buffer cache after the database is started. This turns out to be greater than half of the total system memory on a typical dedicated database server. This setting does not allocate any memory itself; it simply serves as an advisory value for the planner about what should likely be available.
The only...
