Solr Searching Multivalued Fields

I have a multivalued field that appears like this :

<arr name="some_name">
   <str>a-value-1 a-value-2 ....a-value-n</str>
   <str>b-value-1 b-v开发者_StackOverflowalue-2 ....b-value-m</str>
</arr>

where n and m could be arbitrarily large(assume values in each <str> come from a paragraph in a page or something).

How would I search so that the result contains only the documents where all search parameters are contained in the same <str> entity(That is without generating any false positive)?

For instance if the document A has this :

<arr name="some_name">
  <str>london foo-1 foo-2 ...foo-k 2012 foo-k+1 foo-k+2 ...foo-k+n</str>
  <str>beijing bar-1 bar-2 ....bar-j 2008 bar-j+1 bar-j+2 ....bar-j+m</str>
</arr>

what will be the query that would not include document A in the result when searching for the words london AND 2008?

If I were to try something like this some_name:("london AND 2008"~n), I don't know what the value of n would be.

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Consider using a high positionIncrementGap, which will help to separate the multivalued tokens and cross matching across different multivalued entries.
However, even this wont be a foolproof solution.