On Sun, 2010-05-02 at 10:34 -0400, Tom Lane wrote:
Simon Riggs <simon@2ndQuadrant.com> writes:
Not commenting further on that patch, but I notice that when we UPDATE
the toasting algorithm takes no account of the available freespace on
the current block. If we are updating and the space available would make
a difference to the row length chosen, it seems like it would be more
beneficial to trim the row and encourage HOT updates.
That doesn't strike me as a terribly good idea: it would make the
behavior of TOAST significantly more difficult to predict. Also, what
happens if we force a row to a smaller size and then it doesn't fit
anyway (eg because someone else inserted another row on the page while
we were busy doing this)? Spend even more cycles to un-toast back to
the normal size, to be consistent with ordinary cross-page updates?

Pretty much every previous discussion of tweaking the TOAST behavior
has focused on giving the user more control (indeed, the patch you
mention could be seen as doing that). What you're suggesting here
would give the user less control, as well as less predictability.
As long as we've considered it, I'm happy either way. You know I'm
happier with more user control.

Simon Riggs www.2ndQuadrant.com

Search Discussions

Discussion Posts


Follow ups

Related Discussions

Discussion Navigation
viewthread | post
posts ‹ prev | 3 of 5 | next ›
Discussion Overview
grouppgsql-hackers @
postedMay 2, '10 at 12:46p
activeMay 4, '10 at 8:14a



site design / logo © 2021 Grokbase