|Subject||Re: [firebird-support] Re: Data pages and data page slots|
|Author||Walter R. Ojeda Valiente|
Thank you very much Vlad, that is what I was thinking but always is very better to have the explanation of one expert.
On Tue, Dec 13, 2016 at 11:25 AM, hvlad@... [firebird-support] <email@example.com> wrote:
---In firebird-support@yahoogroups. com, <sistemas2000profesional@...> wrote :> When I run GSTAT with the switch -data it shows me numbers after "data pages" and "data page slots".>> Usually these numbers are the same, but ... what happen when they are different?
Physical numbers of data pages stored at kind of array and data of this array are split over
pointer pages. Every item of array also called "slot". Slot could be empty or contain data page
number. When table grows, engine allocates new data pages and put its numbers into empty
slots (allocating pointer pages when necessary). When data pages is freed, slots become empty
but they are still present. Pointer pages freed only when table is dropped. Therefore number of
"data page slots" could be much larger than number of "data pages".
Hope it helps,