Re: storage size of "bit" data type.. - Mailing list pgsql-general

From Michael Glaesemann
Subject Re: storage size of "bit" data type..
Date
Msg-id E464B928-C672-4F6A-9311-63644EA63E36@seespotcode.net
Whole thread Raw
In response to storage size of "bit" data type..  (Alex Mayrhofer <axelm@nona.net>)
Responses Re: storage size of "bit" data type..
List 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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