Many know what a search engine is, what it does and even how it functions using keywords. But to dwell in deeper into the mechanics of familiar search engines that we are fond of such as Google and Yahoo, it is pretty useful to understand more about information retrieval through an open source search engine.

Unlike the layman user search engine that common folks know about, an open source search engine can be considered an intermediate tool component that is part of an ordinary everyday search process. For example, if you are on a Google page and you would like to find out more about the history of football (or soccer if you are from the United States), you simply just type in the keywords and a large array of search results will appear in front of you in less than a second. And within that few mini seconds, Google would utilize the open source search tool to retrieve all the necessary information from the tool's library database (encompassing of thousands of servers) and categorized them neatly in specific indexes. Providing us with the Search Engine Results Pages (SERPs) we have today.

For start-up business trying to make their website prevalent on the internet, Open source search engines can also be regarded to be an alternative to the conventional search engines that we used. For starters, Google and Yahoo may not be practical to these businesses due to its costly fees and the fact that these conventional search engines focus on well established websites. Hence, many small enterprises choose to use open source search engines as they are free, the software is actively maintained and you can customize its programming codes for specific preferences.

Lucene is one of the more established open source search engines out there with a text search engine library that is written purely in Java. Its indispensable software can be used for any application that requires full-text search.

Lucene can be used across platforms, has a configurable storage engine (Codecs) and has many powerful query types such as proximity queries and phrase queries.

Even in 2017, Lucene is still preferred by some employers. Click here to see the demand for lucene in your location.

"It's probably the most advanced library out there today – open source or not," says Shay Banon, the founder of ElasticSearch

Sphinx is an open source full text search server that is programmed with relevant search quality and integration simplicity.

Sphinx allows flexible testing whereby its indexing features include full support for SBCS and UTF-8 encodings, stopword removal and optional hit position removal (hitless indexing); morphology and synonym processing through word forms dictionaries and stemmers; exceptions and blended characters; and many more.

Sphinx has an easy application integration that is derived from 3 different APIs. It has a native library for many programming languages, a pluggable storage engine for MySQL and an application query that uses MySQL client library and syntax.

The demand for Sphinx among employers is not as that of Lucene. To know who is hiring for Sphinix near you, click here.

Xapian, termed as an open source probabilistic information retrieval library, provides a full text search engine library for programmers.

It possesses a wide range of structured Boolean search operators which are allocated based on probabilistic weights. There are also Boolean filters to restrict a probabilistic search.

Xapian's search engine also has the dexterous ability to support the search's word synonyms explicitly and as an automatic form of query expansion.

Also, if you're looking for a fully packaged search engine that is derived upon Xapian, you may install Omega into your site. A great aspect about Xapian is its versatility is that allows you to extend to Omega to meet your needs as they grow.

Below are couple of more open source search engines that could be of your interest.

Indri is an open source search engine that prides itself through its state-of-the-art text search and a rich structured query language for text collections of up to 50 million documents (single machine) or 500 million documents (distributed search). Indri is multi platform and is applicable in Linux, Solaris, Windows and Mac OSX.

Indri is can support UTF-8 encoded text and is able to parse PDF, HTML, XML and TREC documents. It also recognizes text annotations.

Written and designed by the Search Engine Group at RMIT University, Zettair is a compact and fast text search engine which allows you to index and search HTML (or TREC) collections. It also formatted for simplicity as well as speed and flexibility, and one of its fundamental features is the ability to handle large amounts of text.