Solr Review

A key differentiator of Solr is the level of customizability the SearchComponent feature provides.

SearchComponent provides the developer astonishing flexibility in the way search queries are assembled and executed. At the time of writing, there does not appear to be a ElasticSearch equivalent of SearchComponent. source

Whilst ElasticSearch has a number of plugin-points there doesn't appear to be an equivalent of Solr's SearchComponent that enables you to modify the workflow of existing API endpoints.

Solr allows to view average, standard deviation, maximum, minimum, sum of squares of a particular numeric field. It also allows faceting of that numeric field based on the value(s) of other fields.

Solr allows you to group search results. Results can be grouped by:

• Field Value
• Query
• Function Query

You can also collapse multiple results with the same field value down to a single result.

Solr has a faceting feature called pivot facets or 'decision tree facets'. Pivot facets enable you to calculate facets inside a parents facet, for example pivoting on 'size' than 'color' returns 'color' facet counts for each 'size' facet

Solr has a great feature that enables you to use LocalParams to perform more advanced faceting. They provide a way to "localize" information about a specific argument that is being sent to Solr. In other words, LocalParams provide a way to add meta-data to certain argument types such as query strings. From the Solr Wiki:

LocalParams are expressed as prefixes to arguments to be sent to Solr. For example:

Assume we have the existing query parameter

q=solr rocks

We can prefix this query string with LocalParams to provide more information to the query parser, for example changing the default operator type to "AND" and the default field to "title" for the lucene query parser:

q={!q.op=AND df=title}solr rocks

The following services will host Solr for you. The great thing about these services is that they abstract away some of the difficulty of scaling Solr:

• WebSolr
• SolrHQ

Solr allows has the functionality to check and correct spelling mistakes in search queries. The three main implementations are:

• IndexBasedSpellChecker
• WordBreadkSolrSpellChecker
• DirectSolrSpellChecker