Take a look @ KMKLabs Tech Talk Michael Himawan 

Information Retrieval Information retrieval (IR) is finding material (usually documents) of an unstructured nature (usually text) that satisfies an information need from within large collections (usually stored on computers) (2009, An Introduction to Information Retrieval) 

What is Solr ? - an Information Retrieval Machine - is a Car (same with ElasticSearch) - an enterprise search platform How Solr works ? - Solr up (as a service) - Solr index new document or load the current indexed document - Solr returned the Query (search text) from user 

Peeking to Inverted Index Doc 1: Brad work at Jakarta Doc 2: People come to Jakarta for work Term Doc ID Brad 1 work 1,2 at 1 Jakarta 1,2 People 2 come 2 to 2 for 2 

Who used Solr ? 

When we use Solr ? If you want to build a good search engine, use Solr (or others which behave like it) 

Queries per Second (in exp using 10 queries) - Postgre with multiple connection will be slower, (true fact) - but if using the same connection to do multiple queries Postgre can do 29.6% more queries than Solr per second Solr vs Postgresql (by Charles Nagy) 

Query time - Postgre with multiple connection will be slower, (true fact) - Postgresql is faster with 27% than Solr in terms of query time. Solr vs Postgresql (by Charles Nagy) 

Thank you 

Resource - An Introduction to Information Retrieval - http://www.sitepoint.com/using-solarium-solr-search-setup/ - http://stackoverflow.com/questions/10053050/why-is-solr-so-much-faster-than-postgres - http://db-engines.com/en/system/PostgreSQL%3BSolr - http://charlesnagy.info/it/postgresql/postgresql-full-text-search-vs-solr