If your site is available for the Google bot, Google Site Search is easy.
You can also look at the application server for full-text search (for example, in the .NET / SQL environment).
If you want an enterprise search engine platform, check out the open source Solr . With Java, .Net, and a JavaScript API and a REST-based server / service, this open source option is worth a long look.
Do not go too far from the topic, but it helped me visualize when I first answered the same question: site search means three things. One is a search engine; two - search pattern / index (decide what the beast eats and feed); three, search user interface.
Chris warner
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