[Monetdb-developers] BAT sizes

Henning Rode h.rode at cs.utwente.nl
Fri Oct 5 11:14:31 CEST 2007


hej monet-people,

i was a bit puzzled when using the batsize/batdsksize mil-commands on
our pf/tijah index BATs:

our pre_size table is also (void|int). however:

(dbl(batsize("tj_DFLT_FT_INDEX_size1")) /
count(bat("tj_DFLT_FT_INDEX_size1"))).print();
[ 5.1875055810700283 ]

since this seemed a rather strange size for an entry, i also tried:

(dbl(batdsksize(bat("tj_DFLT_FT_INDEX_size1"))) /
count(bat("tj_DFLT_FT_INDEX_size1"))).print();
[ 4.0000030960842796 ]

which looks much more as i expected. but where does the difference come
from? even if i copy the bat:

var t := bat("tj_DFLT_FT_INDEX_size1").copy();
(dbl(batsize(t)) / count(t)).print();
[ 5.1875055810700283 ]

the result remains the same. can anyone explain this? the pre_size BAT
is usually so large that 25% more space requirement would probably matter.

best -henning





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