Question

I have an array containing URL paths, I want to be able to search in my database in a table which one of the fields (labelled “URL”) for the URLs specified in the array.

So I have a simplified version of what I want to achieve.

urls = ["url1", "url2", "url3", "url4", ... ]
urlsInDB = []
results = Link.all
urls.each() do |url|
 if not results.where(:url=>url).blank?
   urlsInDB << url
 end
end

However I know that you cannot call “.where” on a set of results obtained by “.all”. I want to do it this way so that the database is only ever queried once not for each URL in urls as this can have length n and that would require n queries.

Any ideas?

Answer 1

In SQL, you’d do this by saying:

SELECT * FROM links WHERE url IN ('url1', 'url2', 'url3');

You can do this with ActiveRecord by saying:

Link.where(:url => ['url1', 'url2', 'url3'])

If you just want to get an array of URLs that matched, say:

Link.select(:url).where(:url => ['url1', 'url2', 'url3']).map(&:url)
# SQL: SELECT url FROM links WHERE url IN ('url1', 'url2', 'url3')
# => ['url1', 'url2']