On Dec 5, 2007, at 7:23 PM, Michael Glaesemann wrote:
On Dec 5, 2007, at 14:19 , Alex Mayrhofer wrote:i'm trying to find out the storage size for bit(n) data. My initial assumption would be that for any 8 bits, one byte of storage is required.select pg_column_size(B'1') as "1bit", pg_column_size(B'1111') as "4bits", pg_column_size(B'11111111') as "1byte", pg_column_size(B'111111111111') as "12bits", pg_column_size(B'1111111111111111') as "2bytes", pg_column_size(B'11111111111111111') as "17bits", pg_column_size(B'111111111111111111111111') as "3bytes"; 1bit | 4bits | 1byte | 12bits | 2bytes | 17bits | 3bytes ------+-------+-------+--------+--------+--------+-------- 9 | 9 | 9 | 10 | 10 | 11 | 11 (1 row)Looks like there's 8 bytes of overhead as well, probably because a bit string is a varlena type.
Wow, that's screwed up... that's a lot more than varlena overhead:select pg_column_size('a'::text), pg_column_size(1::numeric), pg_column_size(3111234::numeric);
pg_column_size | pg_column_size | pg_column_size
----------------+----------------+----------------
5 | 10 | 12
Apparently it's something related to numeric.
--
Decibel!, aka Jim C. Nasby, Database Architect decibel@xxxxxxxxxxx
Give your computer some brain candy! www.distributed.net Team #1828
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