what is the best Database for keeping tag and content data?

I have a system that contains blobs o开发者_如何转开发f content and a very long list of tags (over 4000) the content are parsed by a separate app, the frequency and location of each tag then is extracted, what is the best database system to store huge amount of content and tags which would then allow searching over such tags?

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I'd take a look at Lucene (and related projects like Solr and ElasticSearch) or Sphinx, that is, text search engines rather than what you would usually refer to as a database.

These engines are geared towards indexing documents - blobs of text, by breaking them down to their many small components ("tokenization"). The problem that you describe - storing a blob and a long list of tags - is in that domain.