Re: Hstore: Query speedups with Gin index

On Sun, Aug 25, 2013 at 10:11:50PM -0400, Tom Lane wrote:
> Michael Paquier <michael(dot)paquier(at)gmail(dot)com> writes:
> > On Thu, Aug 22, 2013 at 11:55 PM, Blake Smith <blakesmith0(at)gmail(dot)com> wrote:
> >> The combined entry is used to support "contains (@>)" queries, and the key
> >> only item is used to support "key contains (?)" queries. This change seems
> >> to help especially with hstore keys that have high cardinalities. Downsides
> >> of this change is that it requires an index rebuild, and the index will be
> >> larger in size.
>
> > Index rebuild would be a problem only for minor releases,
>
> That's completely false; people have expected major releases to be
> on-disk-compatible for several years now. While there probably will be
> future releases in which we are willing to break storage compatibility,
> a contrib module doesn't get to dictate that.
>
> What might be a practical solution, especially if this isn't always a
> win (which seems likely given the index-bloat risk), is to make hstore
> offer two different GIN index opclasses, one that works the traditional
> way and one that works this way.
>
> Another thing that needs to be taken into account here is Oleg and
> Teodor's in-progress work on extending hstore:
> https://www.pgcon.org/2013/schedule/events/518.en.html
> I'm not sure if this patch would conflict with that at all, but it
> needs to be considered.

We can disallow in-place upgrades for clusters that use certain contrib
modules --- we have done that in the past.

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

+ It's impossible for everything to be true. +