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='';


for i in 1..1000 loop

str := str || 'union all select i,i,i from generate_series(1,50000) g(i) ';

end loop;

execute 'select 1,2,3 ' || str;


is it expected behave?

Tested on PostgreSQL 9.1, 9.2, 9.3

It looks so all generated data are saved in memory only.


Pavel Stehule

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