Re: Compressed TOAST Slicing

Some time ago I posted PoC patch with alternative TOAST compression scheme:
instead of "compress-then-chunk" I suggested "chunk-then-compress". It
decrease compression level, but allows efficient arbitrary slicing.

ср, 20 февр. 2019 г., 2:09 Paul Ramsey pramsey@cleverelephant.ca:

> On Sat, Feb 16, 2019 at 7:25 AM Simon Riggs <simon@2ndquadrant.com> wrote:
>
> > Could we get an similarly optimized implementation of -> operator for
> JSONB as well?
> > Are there any other potential uses? Best to fix em all up at once and
> then move on to other things. Thanks.
>
> Oddly enough, I couldn't find many/any things that were sensitive to
> left-end decompression. The only exception is "LIKE this%" which
> clearly would be helped, but unfortunately wouldn't be a quick
> drop-in, but a rather major reorganization of the regex handling.
>
> I had a look at "->" and I couldn't see how a slice could be used to
> make it faster? We don't a priori know how big a slice would give us
> what we want. This again makes Stephen's case for an iterator, but of
> course all the iterator benefits only come when the actual function at
> the top (in this case the json parser) are also updated to be
> iterative.
>
> Committing this little change doesn't preclude an iterator, or even
> make doing one more complicated... :)
>
> P.
>
>