From: | Michael Glaesemann <grzm(at)seespotcode(dot)net> |
---|---|
To: | Alex Mayrhofer <axelm(at)nona(dot)net> |
Cc: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: storage size of "bit" data type.. |
Date: | 2007-12-06 01:23:16 |
Message-ID: | E464B928-C672-4F6A-9311-63644EA63E36@seespotcode.net |
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Lists: | pgsql-general |
On Dec 5, 2007, at 14:19 , Alex Mayrhofer wrote:
> Hi,
>
> 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.
Michael Glaesemann
grzm seespotcode net
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