[hibernate-dev] Coordinates storage in Lucene index for spatial functionality

Mon May 7 04:31:42 EDT 2012

Hi all,

I have done a radian patch/branch and some benchmarks on geonames french
database.

Benchs are on 2k calls each run.

Radians:
run 1
Mean time with Grid : 4.808043092820513 ms
Mean time with Grid + Distance filter : 6.571108878461538 ms
Mean time with DoubleRange : 14.62661525128205 ms
Mean time with DoubleRange + Distance filter : 20.143597923076925 ms

run 2
Mean time with Grid : 5.290368523076923 ms
Mean time with Grid + Distance filter : 6.706567517435897 ms
Mean time with DoubleRange : 14.878960702564102 ms
Mean time with DoubleRange + Distance filter : 20.75806591948718 ms

Degrees:
run 1
Mean time with Grid : 5.101956610769231 ms
Mean time with Grid + Distance filter : 6.548685109230769 ms
Mean time with DoubleRange : 14.767478146153845 ms
Mean time with DoubleRange + Distance filter : 20.668063972820512 ms

run 2
Mean time with Grid : 4.683360031282051 ms
Mean time with Grid + Distance filter : 6.7065247435897435 ms
Mean time with DoubleRange : 14.617140157948716 ms
Mean time with DoubleRange + Distance filter : 20.074868595897435 ms

The radian branch is here for review :
https://github.com/nicolashelleringer/hibernate-search/tree/HSEARCH-923-RADIANS

While moving from degrees to radians I have seen that DSL has still some
work to do.
I shall focus on that now.

Niko

2012/5/3 Sanne Grinovero <sanne at hibernate.org>

>
> On May 3, 2012 10:10 AM, "Emmanuel Bernard" <emmanuel at hibernate.org>
> wrote:
> >
> > How comes the DistanceFilter has to compute the distance for the whole
> corpus?
>
> You're right in that's not always the case, but it's possible. If there
> are more filters enabled and they are executed first, our filter will need
> to do the math only on the matched documents by the previous filters, but
> if there are no other constraints or filters our DistanceFilter might need
> to process all documents in all segments. This happens also when a limit is
> enabled on the collector - although limited to the current index segment -
> when the filter needs to be cached as it needs to evaluate each document in
> the segment.
>
> In our case this DistanceFilter is only applied after RangeQuery was
> applied on both longitude and latitude, so I'm not sure if this is a big
> problem; personally I was just wondering but I'd be fine in keeping this as
> a possible future improvement - but if we go for a separate issue, let's
> keep in mind that that the index format would not be backwards compatible.
>
>
> > By the way the actual storage (say via Hibernate ORM, or Infinispan)
> does not need to store in radian, so we don't need to do a conversion when
> reading an entity.
>
> Right, another reason to index only in whatever format makes querying more
> efficient.
>
> -- Sanne
>
>
> >
> > On 3 mai 2012, at 10:45, Sanne Grinovero wrote:
> >
> > > The reason for my comment is that the code is doing a conversion to
> > > radians in the DistanceFilter, which needs to be extremely efficient
> > > as it's not only applied on the resultset but potentially on the whole
> > > corpus of all Documents in the index.
> > > So even if it's true that conversion would be needed on the final
> > > results, we always expect people to retrieve only a limited amount of
> > > entities (like with pagination), while the index might need to perform
> > > this computation millions of times per query.
> > >
> > > If I look at the complexity of Point.getDistanceTo(double, double), I
> > > get a feeling that that method will hardly provide speedy queries
> > > because of the complex computations in it - this is just speculation
> > > at this point of course, to be sure we'd need to compare them with a
> > > large enough dataset, but it seems quite obvious that storing
> > > normalized radians should be more efficient as it would avoid a good
> > > deal of math to be executed on each Document in the index.
> > >
> > > Also if we assume people might want to use radians in their user data
> > > (I know some who definitely would never touch decimals for such a use
> > > case), there would be no need at all to convert the end result.
> > >
> > > Some more thoughts inline:
> > >
> > > On 3 May 2012 09:12, Nicolas Helleringer <
> nicolas.helleringer at gmail.com> wrote:
> > >> Hi all,
> > >>
> > >> Sanne and I have been wondering about the way the spatial
> > >> branch/module/functionality for Hibernate Search shall store its
> > >> coordinates in the Lucene index.
> > >>
> > >> Today it is implemented with decimal degree for :
> > >> - easy debugging/readability
> > >> - ease of conversion on storage as we want to accept mainly decimal
> degree
> > >> from users data
> > >
> > > Valid points, but consider that "storage" is going to be way slower
> > > anyway, and typically you'll process a Document to evaluate it for a
> > > hit many many orders of magnitude more frequently than the times you
> > > store it.
> > >
> > >>
> > >> Sanne pointed out that when the search is done there is quite a few
> > >> conversion to radians for distance calculation and suggested that we
> may
> > >> store directly coordinates under their radians form.
> > >>
> > >> I have tried a patch to implement this and as I was coding it I feel
> that
> > >> the code was less readable, in the coordinates normalisation mainly
> and
> > >> that there was as many conversion as before.
> > >> Conversions had moved from search to import / export of coordinates
> in and
> > >> out the spatial module scope to user scope.
> > >
> > > I'm sure the amount of points in the code in which they are converted
> > > won't change. I'm concerned about the cardinality of the collections
> > > on which it's applied ;)
> > > "Less readable" isn't nice, but we can work on that I guess?
> > >
> > >>
> > >> What the docs does not tell (yet), is that we are waiting for WGS 84
> (this
> > >> is a coordinate system) decimal degree coordinates input, as these are
> > >> quite a de facto standard (GPS output this way).
> > >
> > > How does it affect this?
> > >
> > >>
> > >> Today this is not the purpose of Hibernate Search spatial initiative
> to
> > >> handle projections. There are opensource libs to handle that on user
> side
> > >> very well (Proj4j)
> > >>
> > >> So. The question is : shall we store as radians or decimal degree ?
> > >>
> > >> Niko
> > >>
> > >> P.S : Hope it is clear. If not ask for more.
> > >
> > > Thanks!
> > > Sanne
> > > _______________________________________________
> > > hibernate-dev mailing list
> > > hibernate-dev at lists.jboss.org
> > > https://lists.jboss.org/mailman/listinfo/hibernate-dev
> >
>