When to definitely use SOLR over Lucene in a Sitecore 7 build?

Question

My client does not have the budget to setup and maintain a SOLR server to use in their production environment. If I understand the Sitecore 7 Content Search API correctly, it i

Answer 1

I think if you are dealing with a customer on a limited budget then Lucene will work perfectly well and perform excellently for the scale of things you are doing. All the things you mention are fully supported by the implementation in Lucene.

In a Sitecore scenario I would begin to consider Solr if:

• You need to index a large number of items - id say 50 thousand upwards - Lucene is happy with these sorts of number but Solr has improved query caching and is designed for these large numbers of items.
• The resilience of the search tier is of maximum business importance (ie the site is purely driven by search) - Solr provides a more robust replication/sharding and failover system with SolrCloud.
• Re-purposing of the search tier in other application is important (non Sitecore) - Solr is a search application so can be accessed over HTTP with XML/JSON etc which makes integration with external systems easier.
• You need some specific additional feature of Solr that Lucene doesn't have.

.. but as you say if you want swap out Lucene for Solr at a later phase, we have worked hard to make sure that the process as simple as possible. Worth noting a few points here:

• While your LINQ queries will stay the same your configuration will be slightly different and will need attention to port across.
• The understanding of how Solr works as an application and how the schema works is important to know but there are some great books and a wealth of knowledge out there.
• Solr has slightly different (newer) analyzers and scoring mechanisms so your search results may be slightly different (sometimes customers can get alarmed by this :P)

.. but I think these are things you can build up to over time and assess with the customer. Im sure there are more points here and others can chime in if they think of them. Hope this helps :)