Re: Re: patch: fix performance problems with repated decomprimation of varlena values in plpgsql
Robert Haas <robertmhaas@gmail.com>
From: Robert Haas <robertmhaas@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>, Pavel Stehule <pavel.stehule@gmail.com>, Noah Misch <noah@leadboat.com>, Kevin Grittner <Kevin.Grittner@wicourts.gov>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2011-01-25T15:33:35Z
Lists: pgsql-hackers
On Tue, Jan 25, 2011 at 10:03 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote: > Heikki Linnakangas <heikki.linnakangas@enterprisedb.com> writes: >> Detoasting on first usage, ie. exec_eval_datum(), seems the best to me. >> Compared to detoasting on assignment, it avoids the performance >> regression if the value is never used, and I don't think checking if the >> value is toasted at every exec_eval_datum() call adds too much overhead. > > The arguments that were made against this were about maintenance costs > and code footprint. Claims about performance are not really relevant, > especially when they're entirely unsupported by evidence. How much evidence do you need to the effect that detoasting a value that's never used will hurt performance? -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company