Re: TOAST usage setting

Alvaro Herrera wrote:
> > > >> > Strangely, 128 bytes seems to be the break-even point for TOAST and
> > > >> > non-TOAST, even for sequential scans of the entire heap touching all
> > > >> > long row values. I am somewhat confused why TOAST has faster access
> > > >> > than inline heap data.
> > >
> > > Is your database initialized with C locale? If so then length(text) is
> > > optimized to not have to detoast:
> > >
> > > if (pg_database_encoding_max_length() == 1)
> > > PG_RETURN_INT32(toast_raw_datum_size(str) - VARHDRSZ);
> >
> > Wow, we optimized length(). OK, will run the test with
> > substring(t,1,1).
>
> Be careful about the compression! It might be a good idea to run the
> test once with the column set to uncompressible (SET STORAGE EXTERNAL?),
> and again with it as compressible.

My test uses random data, which I figured was a close to real-world as I
could get, and I have a test that makes sure the data was pushed to the
TOAST table. Should I still try EXTERNAL?

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://www.enterprisedb.com

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