[Firebird-devel] Count(*) faster without index ?

[Derryck w. <der...@ce...>]

Hi ,

I always assumed using an index works faster ( well  it is faster when the 
count volume is low).

but this case proved otherwise (when the counted volume gets very high).

select count(*) as count_order
from   lineitem
where  l_shipdate <= date '1998-12-01' - 90;

With index  on l_shipdate

PLAN (LINEITEM INDEX (LINEITEM_SHIPDATE))

Current memory = 4633132
Delta memory = 3696420
Max memory = 4633132
Elapsed time= 39.14 sec
Buffers = 75
Reads = 111237
Writes 0
Fetches = 11837255



Without index works faster !

PLAN (LINEITEM NATURAL)

Current memory = 1009304
Delta memory = 72592
Max memory = 1156720
Elapsed time= 35.66 sec
Buffers = 75
Reads = 107563
Writes 0
Fetches = 12217691


tested on   2.1 and 2.1.1RC1

Can  i put this in the tracker ?


Regards,
Derryck