Re: Hstore: Query speedups with Gin index

Blake,

Teodor will review your patch, but I have one consideration about the patch
in context of future hstore, which supports hierarchical structures. In
that case overhead of composite keys will be enormous and the only way in
this direction is to think about idea suffix array instead of btree to
store keys. But this is another big task and I afraid to think about this
now.

Oleg

On Mon, Sep 9, 2013 at 6:55 PM, Blake Smith <blakesmith0(at)gmail(dot)com> wrote:

> Thanks for getting back to me about this change Oleg. I took your advice
> and reworked the patch by adding a new hstore gin opclass
> (gin_hstore_combined_ops) and leaving the functionality of the default
> hstore gin opclass the same. This should prevent the on-disk compatibility
> issues from the first patch, and allow users to select the different
> indexing method when they build the index. The hstore regression suite is
> passing for me locally with the --enable-cassert configure flag. Please let
> me know what you think and if there is any other work that would need to be
> done (style cleanups, updating documentation, etc) to get this merged.
>
> Thanks!
>
> Blake
>
>
>
>
>
>
> On Fri, Sep 6, 2013 at 1:47 PM, Oleg Bartunov <obartunov(at)gmail(dot)com> wrote:
>
>> Blake,
>>
>> I think it's better to implement this patch as a separate opclass, so
>> users will have option to choose indexing.
>>
>> Oleg
>>
>>
>> On Tue, Sep 3, 2013 at 6:24 PM, Blake Smith <blakesmith0(at)gmail(dot)com>wrote:
>>
>>> Thanks for the feedback everyone. I've attached the patch that we are
>>> now running in production to service our hstore include queries. We rebuilt
>>> the index to account for the on-disk incompatibility. I've submitted the
>>> patch to commitfest here:
>>> https://commitfest.postgresql.org/action/patch_view?id=1203
>>>
>>> Michael: I don't have a formal benchmark, but several of our worst
>>> queries went from 10-20 seconds per query down to 50-400 ms. These are
>>> numbers we've seen when testing real production queries against our
>>> production dataset with real world access patterns.
>>> Oleg: Thanks for your thoughts on this change. As for the spgist / gin
>>> work you're doing, is there anything you need help with or are you still in
>>> the research phase? I'd love to help get something more robust merged into
>>> mainline if you think there's collaborative work to be done (even if it's
>>> only user testing).
>>>
>>> Thanks,
>>>
>>> Blake
>>>
>>>
>>>
>>>
>>> On Wed, Aug 28, 2013 at 12:40 PM, Andres Freund <andres(at)2ndquadrant(dot)com>wrote:
>>>
>>>> On 2013-08-28 13:31:22 -0400, Bruce Momjian wrote:
>>>> > 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.
>>>>
>>>> But that really cannot be acceptable for hstore. The probably most
>>>> widely used extension there is.
>>>>
>>>> Greetings,
>>>>
>>>> Andres Freund
>>>>
>>>> --
>>>> Andres Freund http://www.2ndQuadrant.com/
>>>> PostgreSQL Development, 24x7 Support, Training & Services
>>>>
>>>
>>>
>>>
>>> --
>>> Blake Smith
>>> http://blakesmith.me
>>> @blakesmith
>>>
>>>
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>>>
>>
>
>
> --
> Blake Smith
> http://blakesmith.me
> @blakesmith
>