Now that we know what text tagging is and have seen some algorithms that can be used for text tagging, let us learn how text tagging is done using Solr. There is an open source library, Solr Text Tagger, that can be used for text tagging in Solr.
The library can be referred to at the following link: https://github.com/OpenSextant/SolrTextTagger.
Text tagging via this library involves two layers of FSTs. A word dictionary FST is used to hold each unique word. This enables integers to be used as substitutes for a word (
char). For example, the word
New will be mapped to
13452 and another word
Delhi will be mapped to
New => 13452 Delhi => 5223316
The call to Lucene's FST library
Util.getByOutput(<fst object>, ...