Re: Higher TOAST compression.

Laurent Laborde <kerdezixe@gmail.com> wrote: 
> Kevin Grittner<Kevin.Grittner@wicourts.gov> wrote:
>> How about two new ALTER TABLE actions:
>>
>>   ALTER [ COLUMN ] column SET COMPRESSION_THRESHOLD integer
>>   ALTER [ COLUMN ] column SET EXTERNAL_THRESHOLD integer
>> Laurent, would something like this address your needs?
> Certainly !
> We already alter storage type on some column, adding some more won't
> be a problem. :)
> 
> But... on which version are you planning to do that ?
The patch, if there's consensus that it's a good idea, would be for
8.5.  Since it is new functionality, there wouldn't be a back-port to
prior releases.  Of course, I wouldn't be starting to work on such a
patch until after our current code commit phase, which ends August
15th.
> We stay on Pg 8.3 until the slony developpers find a better upgrade 
> solution.
> 
> The proposed solution sound really good to me.
> But, for now, if i could have a simple patch for 8.3 (eg: changing a
> #define in the source code), i'd be very happy :)
> 
> Is it ok to just change TOAST_TUPLES_PER_PAGE ?
The thing that worries me about that is that it would tend to force
more data to be stored out-of-line, which might *increase* your I/O;
since the whole point of this exercise is to try to *decrease* it,
that seems pretty iffy.  However, once we get to the end of code
commit, I might be able to give you a little one-off patch that would
be more aggressive about compression without affecting out-of-line
storage.  Hard-coded, like what you're talking about, but with a
little more finesse.
-Kevin