Christopher Kings-Lynne wrote:
The point here is that if tuples require 50 bytes, and there are 20
bytes free on a page, pgstattuple counts 20 free bytes while FSM
ignores the page. Recording that space in the FSM will not improve
matters, it'll just risk pushing out FSM records for pages that do
have useful amounts of free space.
Maybe an overloaded pgstattuple function that allows you to request FSM
behavior?
That's a nice idea - could also do equivalently by adding an extra
column "usable_free_space" or some such, and calculating this using FSM
logic.
Cheers
Mark
---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
