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https://issues.apache.org/jira/browse/SOLR-2155?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=13185172#comment-13185172
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Srikanth Kallurkar commented on SOLR-2155:
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Hi David, Apologies for taking a long time to reply. I incorporated your
suggestions and did see some speedup. I started with geohash length at 12 and
got reasonable speed up for 8. T
But I am bit confused by (1) accuracy associated with length and (2) the query
time operation in this patch.
(1) So, is the accuracy associated with how big/small an enclosing box is?
(2) The entire geohash field is loaded into memory at query time. Is this done
because for the lat-lon comparisons, the patch cannot use lucene string
matching mechanisms. Also, because the whole field is in memory, how are
updates to the index handled. Meaning, if new lat-lons are added, do they get
added to the in-memory geohashes.
Thanks,
Srikanth
Geospatial search using geohash prefixes
Key: SOLR-2155
URL: https://issues.apache.org/jira/browse/SOLR-2155
Project: Solr
Issue Type: Improvement
Reporter: David Smiley
Attachments: GeoHashPrefixFilter.patch, GeoHashPrefixFilter.patch,
GeoHashPrefixFilter.patch,
SOLR-2155_GeoHashPrefixFilter_with_sorting_no_poly.patch, SOLR.2155.p3.patch,
SOLR.2155.p3tests.patch, Solr2155-1.0.2-project.zip,
Solr2155-1.0.3-project.zip, Solr2155-for-1.0.2-3.x-port.patch
There currently isn't a solution in Solr for doing geospatial filtering on
documents that have a variable number of points. This scenario occurs when
there is location extraction (i.e. via a gazateer) occurring on free text.
None, one, or many geospatial locations might be extracted from any given
document and users want to limit their search results to those occurring in a
user-specified area.
I've implemented this by furthering the GeoHash based work in Lucene/Solr
with a geohash prefix based filter. A geohash refers to a lat-lon box on the
earth. Each successive character added further subdivides the box into a 4x8
(or 8x4 depending on the even/odd length of the geohash) grid. The first
step in this scheme is figuring out which geohash grid squares cover the
user's search query. I've added various extra methods to GeoHashUtils (and
added tests) to assist in this purpose. The next step is an actual Lucene
Filter, GeoHashPrefixFilter, that uses these geohash prefixes in
TermsEnum.seek() to skip to relevant grid squares in the index. Once a
matching geohash grid is found, the points therein are compared against the
user's query to see if it matches. I created an abstraction GeoShape
extended by subclasses named PointDistance... and CartesianBox to support
different queried shapes so that the filter need not care about these details.
This work was presented at LuceneRevolution in Boston on October 8th.
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