Solr - how to “group by” and “limit”?

Question

Say I indexed the following from my database:

======================================
| Id |  Code | Description           |
=================================         


        

Answer 1

Have a look at field collapsing, available in Solr 4.0. Sorting groups on relevance: group.sort=score desc.

Answer 2

add the following field to your query

• 'group':'true',
• 'group.field':'source',
• 'group.main':'true',
• 'group.limit':10,

Answer 3

http://XXX.XXX.XXX.XXX:8080/solr/autocomplete/select?q=displayterm:new&wt=json&indent=true&q.op=and&fl=displayterm&group=true&group.field=displayterm&rows=3&start=0

Note:

Response: start -> response start your id. rows -> how do you wat number of rows .

Exp 
 1 step 
  &start=0&rows=3
2 step 
  &start=3&rows=3
3 step
  &start=6&rows=3
etc.


{
  "responseHeader":{
    "status":0,
    "QTime":1,
    "params":{
      "fl":"displayterm",
      "indent":"true",
      "start":"0",
      "q":"displayterm:new",
      "q.op":"and",
      "group.field":"displayterm",
      "group":"true",
      "wt":"json",
      "rows":"3"}},
  "grouped":{
    "displayterm":{
      "matches":231,
      "groups":[{
          "groupValue":null,
          "doclist":{"numFound":220,"start":0,"docs":[
              {
                "displayterm":"Professional News"}]
          }},
        {
          "groupValue":"general",
          "doclist":{"numFound":1,"start":0,"docs":[
              {
                "displayterm":"General News"}]
          }},
        {
          "groupValue":"delhi",
          "doclist":{"numFound":2,"start":0,"docs":[
              {
                "displayterm":"New Delhi"}]
          }}]}}}

Answer 4

The simplest way to achieve what you want is to use Solr grouping capabilities also called Field Collapsing. You would have to add the following parameters to your query:

• group=true - that would turn on the grouping module
• group.field=Code - that would tell Solr on which field the grouping should be done
• rows=10 - that would tell Solr to limit the number of unique groups to 10 at max

If you would like to page through groups you should use the rows and start parameter. To control the results inside the groups themselves you would use group.limit and group.offset.

Hopefully that helps :)