Re: TOASTed size

On Wed, 2007-12-05 at 08:24 +0000, Gregory Stark wrote:
> "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
>
> > Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> >> I'm thinking that there isn't any way currently of working out how big a
> >> compressed toast object is?
> >
> > pg_column_size() ?
>
> I was going to send the same thing but I think he's looking for the compressed
> size of *external* data.
>
> In fact there isn't really any convenient way to find out something is stored
> external. pg_column_size reports the toast raw size of externally stored data.
>
> There does seem to be a need for a more general pg_column_info which returns a
> tuple (external bool, rawsize integer, storedsize integer).

That sounds more like what I was after.

So let me check my understanding: For TOASTed data pg_column_size()
tells you how many bytes the column value occupies when decompressed. So
there isn't any way of finding out how many bytes a column value
actually occupies when it is both compressed and external?

--
Simon Riggs
2ndQuadrant http://www.2ndQuadrant.com