This is a 32 bit CPU by the way.
Consider this :
- There are 100K rows
- The CPU executes about 3 billion instructions per second if everything
is optimum
- "SELECT sum(n) FROM test", takes, say 60 ms
This gives about 1800 CPU ops per row.
A Float addition versus an Int addition is a drop in the sea.
I believe the marked difference between Floats/Ints (faster) and
Numeric/Bigint (slower) comes from being passed by value or by pointers.
A single access which misses the CPU cache and has to go fetch data from
the real RAM spends a lot more cycles than the simple loops in a NUMERIC
addition which will hit L1 cache.
Nowadays cache access patterns matter more than how many actual CPU
instructions are executed...
forum_bench=> SELECT sum(i) FROM test;
Temps : 46,589 ms
forum_bench=> SELECT sum(f) FROM test;
Temps : 63,865 ms
forum_bench=> SELECT sum(b) FROM test;
Temps : 157,018 ms
forum_bench=> SELECT sum(n) FROM test;
Temps : 124,816 ms
