What is an AND-query and how does it use multiple posting lists?
An AND-query finds documents containing all terms (e.g., 'python' AND 'testing'). Fetch the posting lists for each term and intersect them—iterate the smallest list, checking membership in the others. If the posting lists are sorted, you can merge them in O(n + m) time without a hash table.
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The Inverted IndexA sorted dictionary mapping terms to document IDs. Transform search from O(corpus size) to O(1) lookup, enabling full-text search at scale.
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