On 05/08/14 17:56, Mark Kirkwood wrote:



Adding in the 'if' in the float8 case increases run time to 4s. So looks
like plpgsql might have a slightly higher cost for handling added
conditionals. Be interesting to dig a bit more and see what is taking
the time.


Thinking about this a bit more, I wonder if the 'big O' has added some optimizations in PL/SQL for trivial conditionals - i.e you are adding:

IF (0 = 0) THEN

END IF;

...it may be going...'Ah yes, always true...so remove'!

So it might be interesting to try some (hopefully not so easily removable) non trivial ones like:


DO LANGUAGE plpgsql $$ DECLARE
DECLARE i integer;
BEGIN
FOR i IN 1..10000000 LOOP
  IF (i%100 = 0) THEN
    NULL;
  END IF;
END LOOP;
END $$;

Now I guess there is the chance that PL/SQL might understand that NULL inside a loop means it can remove it...so you may need to experiment further. The point to take away here is that for interesting loops and conditions - there may be not such a significant difference!

Regards

Mark


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