[SERVER-10451] 2dsphere default parameters are poor Created: 07/Aug/13  Updated: 10/Dec/14  Resolved: 01/May/14

Status: Closed
Project: Core Server
Component/s: Geo
Affects Version/s: None
Fix Version/s: None

Type: Improvement Priority: Major - P3
Reporter: Stephen Remde Assignee: hari.khalsa@10gen.com
Resolution: Duplicate Votes: 0
Labels: indexing
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Duplicate
duplicates SERVER-10363 User should be able to specify 2dsphe... Closed
Participants:

 Description   

https://github.com/mongodb/mongo/blob/master/src/mongo/db/index/s2_access_method.cpp#L45

_params.maxCellsInCovering = 50;

50 seems ludicrously high.

See https://code.google.com/p/s2-geometry-library/source/browse/geometry/s2regioncoverer.h#88



 Comments   
Comment by Greg Studer [ 18/Apr/14 ]

> 2dsphere default parameters are poor
Certainly this will depend on the application.

> 50 seems ludicrously high.
I'm not sure that's warranted - according to the table in the source, this will generate covered regions of about 1.25x the shape itself, and shape testing is expensive. If your shapes are distributed widely the trade-off may be different. Note that 50 is the maximum cell covering - it will only have any effect for complex shapes.

We plan on better exposing this knob, however, see linked ticket.

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