Re: varchar as primary key

William Garrison wrote:
> I don't recommend it.  There are better ways to store UUIDs:
>
> char(32)    <-- Easy to work with, fixed length, inefficient
> varchar(32) <-- 4 bytes larger due to variable size
> bytea()     <-- 20 bytes, variable length
> bit(128)    <-- 16 bytes, optimal
>
> I don't like char() or varchar() because of case-senstivity and
> inefficiency.
>
> We used bytea, and created a small function byte2guid() and guid2byte()
> to handle converting to/from strings when working at a SQL prompt.  But
> the production code doesn't use those.  In retrospect, I would like to
> have tried BIT(128) since I think fixed-length columns perform better
> than variable-length columns.

FWIW, in Postgres, all those types are stored with the word length in
front of each datum.  We don't use the column maximum length as a cue
for the storage of each individual datum.  So the two first items you
list above are stored identically.

--
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support