I am in the process of deciding which engine to use to incorporate extensive search features on my database entries into my site. I have been suggested Zend_Lucene, but am debating between Google Site Search.
The question I forgot to ask was will Google Site Search provide me with database searching ability?
The question I forgot to ask was will Google Site Search provide me with database searching ability?
No, Google indexes mainly web pages and certain types of documents (doc, pdf, etc.). You must expose the database content through webpages to have them indexed.
Think about it, let's say Google indexed databases and found a match in some particular row of a table. Where would it take the user?
In terms of a site search, if you have a database-driven site, then any of the searchable information in the DB should already be embedded in the page. The only reason most sites' internal search engines search the database is because it's more convenient, as spidering, parsing webpages, interpreting their semantic structure (title, headings, content, etc.), and then indexing the pages is a complex and difficult process. OTOH, a database is already indexed and its structure provides semantic information about the data.
However, Google has already solved the problem of spidering, parsing, indexing and searching webpages. So if you have properly marked up, semantically structured webpages, then it should make no difference. Google will probably offer even better/faster results than what you yourself can implement using full-text search just because of their synonym replacement & natural language processing algorithms, advanced search operators, and other features.
Now, if you're trying to implement something like a VIN search, or a highly specialized search engine for a particular domain (e.g. an industry knowledgebase), then you may be better off implementing your own database search engine. But then you're not implementing a site search anymore.