On 09/28/2015 05:28 PM, Marti Raudsepp wrote:
Note that Alexander Korotkov already started work in 2013 on a
somewhat similar feature called partial sort:
http://www.postgresql.org/message-id/CAPpHfdscOX5an71nHd8WSUH6GNOCf=V7wgDaTXdDd9=gon-...@mail.gmail.com
In particular, see the 2nd patch for KNN sort -- it uses known
bounding boxes from the GiST index for sorting, which in many ways is
similar to min/max BRIN ranges.
*partial-knn-1.patch*
KNN-GiST provides ability to get ordered results from index, but this order
is based only on index information. For instance, GiST index contains
bounding rectangles for polygons, and we can't get exact distance to
polygon from index (similar situation is in PostGIS). In attached patch,
GiST distance method can set recheck flag (similar to consistent method).
This flag means that distance method returned lower bound of distance and
we should recheck it from heap.
Unfortunatley this work has stalled.
No, that was actually committed for 9.5. It's this item in the release
notes:
Allow queries to perform accurate distance filtering of
bounding-box-indexed objects (polygons, circles) using GiST indexes
(Alexander Korotkov, Heikki Linnakangas)
Previously, a common table expression was required to return a large
number of rows ordered by bounding-box distance, and then filtered
further with a more accurate non-bounding-box distance calculation.
- Heikki
--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers
