[postgis-users] Extent on multiple tables

Markus Schaber schabi at logix-tt.com
Fri Oct 21 07:52:20 PDT 2005

Hi, Strk,

strk at refractions.net wrote:
[extent() and memory usage]
>>My local test here with a 35 million row table seems to prove this, as
>>the postmaster has a constant memory usage of 17M during the whole
>>sequential table scan.
> Happy to know, thank you ;)
> Did you try with the subselect as well ?

Yes, it seems the same. The two UNION ALL queries seem to be processed
sequential. As the ALL keyword is given, there's no duplicate
elimination, and thus there's no need to keep anything in memory.


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