Did you know that you can facet over the same field more than once? Did you know that you can rename the facet field? Did you know that you have display the facet with different filters?

Let’s say I want to look at the number of StackOverflow answers for recent questions as compared to the number of answers across all questions ever asked. I did this be creating a filter query tagged with “moreRecent.” And then I faceted over the AnswerCount field twice, once with the alias of RecentAnswerCount and once with the alias of TotalAnswerCount. The later facet excluded the “moreRecent” filter query.

Here’s the query:

http://localhost:8983/solr/collection1/select
?q=*:*
&facet=on
&fq={!tag=moreRecent}CreationDate:[2011-08-05T19:34:49.473Z TO NOW]
&facet.field={!key=RecentAnswerCount}AnswerCount
&facet.field={!key=TotalAnswerCount ex=moreRecent}AnswerCount

And here is the response:

<lst name="facet_fields">
        </lst><lst name="RecentAnswerCount">
            <int name="2">2543</int>
            <int name="1">2059</int>
            <int name="3">1831</int>
            <int name="4">1015</int>
            <int name="5">514</int>
            <int name="6">222</int>
            <int name="7">114</int>
            <int name="0">95</int>
            <int name="8">77</int>
            <int name="9">44</int>
            <int name="10">24</int>
            <int name="11">12</int>
            <int name="12">9</int>
            <int name="14">8</int>
            <int name="13">6</int>
            <int name="15">4</int>
            <int name="16">4</int>
            <int name="18">3</int>
            <int name="17">2</int>
            <int name="19">2</int>
            <int name="21">2</int>
            <int name="22">2</int>
            <int name="20">1</int>
            <int name="23">1</int>
            <int name="25">1</int>
            <int name="26">1</int>
            <int name="28">1</int>
            <int name="24">0</int>
            <int name="42">0</int>
            <int name="116">0</int>
        </lst>
        <lst name="TotalAnswerCount">
            <int name="2">4862</int>
            <int name="3">3729</int>
            <int name="1">3582</int>
            <int name="4">2116</int>
            <int name="5">1172</int>
            <int name="6">560</int>
            <int name="7">297</int>
            <int name="8">183</int>
            <int name="0">173</int>
            <int name="9">109</int>
            <int name="10">62</int>
            <int name="11">38</int>
            <int name="12">26</int>
            <int name="14">19</int>
            <int name="13">16</int>
            <int name="15">12</int>
            <int name="16">7</int>
            <int name="18">6</int>
            <int name="19">5</int>
            <int name="21">5</int>
            <int name="17">3</int>
            <int name="22">3</int>
            <int name="20">2</int>
            <int name="23">1</int>
            <int name="24">1</int>
            <int name="25">1</int>
            <int name="26">1</int>
            <int name="28">1</int>
            <int name="42">1</int>
            <int name="116">1</int>
        </lst>