one my customer reported a "out of memory" issue. After investigation he found a main problem in large query that uses a lot of union all queries. He wrote a self test:
do $$
declare i integer;str text='';
begin
for i in 1..1000 loop
str := str || 'union all selecti,i,i fromgenerate_series(1,50000) g(i) ';
end loop;
execute 'select 1,2,3 ' || str;
end; $$
is it expected behave?
Tested on PostgreSQL 9.1, 9.2, 9.3
It looks so all generated data are saved in memory only.
