Hello,
I would like to ask from your experience which would be the best "generic" method for checking if row sets of a certain condition exists in a PLPGSQL function.
I know of 4 methods so far (please feel free to add if I missed out any others)
I know of 4 methods so far (please feel free to add if I missed out any others)
1) get a count (my previous experience with ORCL shaped this option)
select count(*) into vcnt
from table
where <<condition>>
from table
where <<condition>>
if vcnt >0 then
do X
else
do y
end if
end if
Cons : It seems doing a count(*) is not the best option for PG
2) Use a non-count option
select primary_key_Col into vcnt
from table
where <<condition>>
from table
where <<condition>>
if found then
do X
else
do y
end if
end if
Cons :Some people seems not to prefer this as (AFAIU) it causes a plpgsql->sql->plpgsql switches
3) using perform
4) using exists3) using perform
perform primary_key_Col into vcnt
from table
where <<condition>>
from table
where <<condition>>
if found then
do X
else
do y
end if
end if
Seems to remove the above (item 2) issues (if any)
if exists ( select 1 from table where <<condition>> ) then
do x
else
do y
end if
end if
My question is what would be the best (in terms of performance) method to use? My gut feeling is to use option 4 for PG. Am I right or is there any other method?
Thanks in advance
Anil
