Greg Stark wrote:
Martijn van Oosterhout <> writes:

To be honest, it seems like a lot of work to save the four bytes of
overhead for the varlena structure on disk if you're going to need it
in memory anyway. And anything like RAW(16) which people want for
UUIDs, if it's going to have a lot of functions associated with it, may
as well just be a new type.

For large databases storage density leads directly to speed. Saving four bytes
of overhead on a 16-byte data structure would mean a 20% speed increase. Even
if that's only helpful on a tenth of the columns you're still talking about a
2% speed increase for all queries on the table. A lot of databases use CHAR(1)
for flags. The overhead is even worse there.

I have to concur with this. Assume you use a bytea for a UUID that in turn is used as a primary key. The extra overhead will be reflected in all indexes, all foreign keys, etc. In a normalized database some tables may consist of UUID columns only.

Thomas Hallgren

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