(initial issue description moved to comment)

as discussed in email...
http://www.nabble.com/Re%3A-Date-facetting-and-ranges-overlapping-p12928374.html

: I'm now using date facetting to browse events. It works really fine
: and is really useful. The only problem so far is that if I have an
: event which is exactly on the boundary of two ranges, it is referenced
: 2 times.

yeah, this is one of the big caveats with date faceting right now ... i
struggled with this a bit when designing it, and ultimately decided to
punt on the issue. the biggest hangup was that even if hte facet counting
code was smart about making sure the ranges don't overlap, the range query
syntax in the QueryParser doesn't support ranges that exclude one input
(so there wouldn't be a lot you can do with the ranges once you know the
counts in them)

one idea i had in SOLR-258 was that we could add an "interval" option that
would define how much to add to the "end" or one range to get the "start"
of another range (think of the current implementation having interval
hardcoded to "0") which would solve the problem and work with range
queries that were inclusive of both endpoints, but would require people to
use "-1MILLI" a lot.

a better option (assuming a query parser change) would be a new option
thta says wether each computed range should be enclusive of the low poin,t
the high point, both end points, neither end points, or be "smart" (where
smart is the same as "low" except for the last range where the it includes
both)

(I think there's already a lucene issue to add the query parser support, i
just haven't had time to look at it)

The simple workarround: if you know all of your data is indexed with
perfect 0.000second precision, then put "-1MILLI" at the end of your start
and end date faceting params.

Additional idea that i like much better then the "interval" idea i had a while back, transcribed from email so it's not lost to the ages...

I think the semantics that might make the most sense is to add a
multivalued "facet.date.include" param that supports the following
options: all, lower, upper, edge, outer

• "all" is shorthand for lower,upper,edge,outer and is the default (for back compat)
• if "lower" is specified, then all ranges include their lower bound
• if "upper" is specified, then all ranges include their upper bound
• if "edge" is specified, then the first and last ranges include their edge bounds (ie: lower for the first one, upper for the last one) even if the corrisponding "upper"/"lower" option is not specified.
• the "between" count is inclusive of each of the start and end bounds iff the first and last range are inclusive of them
• the "before" and "after" ranges are inclusive of their respective bounds if:
  • "outer" is specified ... OR ...
  • the first and last ranges don't already include them

so assuming you started with something like (specific dates and durrations shortend for readability)...

facet.date.start=1 & facet.date.end=3 & facet.date.gap=+1 & facet.date.other=all

...your ranges would be...

[1 TO 2], [2 TO 3] and [* TO 1], [1 TO 3], [3 TO *]

The following params would change the ranges in the following ways...

w/ facet.date.include=lower ...
  [1 TO 2}, [2 TO 3} and [* TO 1}, [1 TO 3}, [3 TO *]

w/facet.date.include=upper ...
  {1 TO 2], {2 TO 3] and [* TO 1], {1 TO 3], {3 TO *]

w/ facet.date.include=lower&facet.date.include=edge ...
  [1 TO 2}, [2 TO 3] and [* TO 1}, [1 TO 3], {3 TO *]

w/ facet.date.include=upper&facet.date.include=edge ...
  [1 TO 2], {2 TO 3] and [* TO 1}, [1 TO 3], {3 TO *]

w/ facet.date.include=upper&facet.date.include=outer ...
  {1 TO 2], {2 TO 3] and [* TO 1], {1 TO 3], [3 TO *]

...etc.

initial proposal: http://old.nabble.com/RE%3A-Date-Facet-duplicate-counts-p27331578.html

Spurred on by recent email threads about this, i sat down and got the previously mentioned design working (with tests!)

this patch implements the "facet.date.include" param mentioned about with the specified semantics. the only change is that i discovered facet.date.other=before and facet.date.other=after don't currently included the start/end (respectively) range boundaries ... so i made the default for facet.date.include be [lower,upper,edge] for back compatibility.

I think this approach makes more sense then the proposal in SOLR-1402 because these semantics make it easy to always get a series of ranges (including the before/after ranges) that are "adjacent" w/o overlapping (using either [lower], [lower,edge], [upper], or [upper,edge])

updated patch to reflect some changes yonik committed to the test

i plan to commit soon .. my only hesitation is the name of the options, but those cna be changed easily.

Committed revision 940556.

Correcting Fix Version based on CHANGES.txt, see this thread for more details...

http://mail-archives.apache.org/mod_mbox/lucene-dev/201005.mbox/%3Calpine.DEB.1.10.1005251052040.24672@radix.cryptio.net%3E

reopening to track backport to 3x

Committed revision 980604. - merged to 3x branch

Bulk close for 3.1.0 release