Faceted Dates

[Ryan McKinley]

I would like to use faceted browsing to group documents by year,
month, and day.  I can think of a few ways to do this, but I'd like to
see what folks think before i start down the wrong track.

Option 1:
Add three fields, one for year, month, day.  Something like:

<field name="addedTime" type="date" indexed="true" stored="true" />
<field name="addedTimeYEAR" type="string" ... />
<field name="addedTimeMONTH" type="string" ... />
<field name="addedTimeDAY" type="string" ... />

then use copyField to generate the various versions:
<copyField source="addedTime" dest="addedTimeYEAR"/>
<copyField source="addedTime" dest="addedTimeMONTH"/>
<copyField source="addedTime" dest="addedTimeDAY"/>

this would somehow convert the original date format for each copy:
addedTime      = "2007-01-08T21:36:15.635Z"
addedTimeYEAR  = "2007"
addedTimeMONTH = "2007-01"
addedTimeDAY   = "2007-01-08"

Perhaps this requires a custom FieldType for Y/M/D to convert the
larger string to the smaller one.

pros:
* Can use SimpleFacets directly
cons:
* seems messy.  particularly since i have multiple fields i'd like to
have the same behavior.


Option 2:
Add an analyzer to the date field that adds multiple Tokens with
various resolutions, then write a custom faceter that knows a string
length 4=year, y=month, 10=day.  Or, perhaps it could look at the
token name.

schema.xml:

 <fieldtype name="fdate" class="solr.DateField">
   <analyzer type="index" class="...DateFacetAnalyzer"/>
 </fieldtype>

DateFacetAnalyzer:
Token t = new Token( date, 0, date.length(), "original" );
t.setPositionIncrement( 0 );
tokens.add( t );

t = new Token( date, 0, 4, "year" );
t.setPositionIncrement( 0 );
tokens.add( t );

t = new Token( date, 0, 7, "month" );
t.setPositionIncrement( 0 );
tokens.add( t );

...

pros:
* simple / reusable
cons:
* I don't fully understand how it would affect search & sorting

Any thoughts / pointers / advice?

thanks
ryan