How to select distinct field values using Solr?

Question

I would like to do the equivalent of this SQL but with Solr as my data store.

SELECT
   DISTINCT txt
FROM
   my_table;

What syntax would fo

Answer 1

Use the StatsComponent with parameter stats.calcdistinct to get a list of distinct values for a certain field:

Solr 7 https://lucene.apache.org/solr/guide/7_7/the-stats-component.html

Solr 6 https://cwiki.apache.org/confluence/display/solr/The+Stats+Component

It will also give you the count of distinct values. stats.calcdistinct is probably available since 4.7.

http://wiki.apache.org/solr/StatsComponent is outdated as it does not cover stats.calcdistinct

Example

/select?stats=on&stats.field=region&rows=0&stats.calcdistinct=true

"stats":{
  "stats_fields":{
    "region":{
      "min":"GB",
      "max":"GB",
      "count":20276,
      "missing":0,
      "distinctValues":["GB"],
      "countDistinct":1}}}}

Difference to Facets

In case of facets you need to know the count to request all, or you set the facet.limit to something really high and count the result yourself. Also, you need a string field for making facets work the way you need it here.