1. One or more tangible computer storage media storing computer-useable instructions that, when used by a computing device, cause the computing device to perform a method comprising: receiving a search query; reformulating the search query to identify one or more atoms used to query a search index, the search index storing a plurality of atoms, the plurality of atoms comprising one or more n-grams, one or more n-tuples, and one or more near n-tuples; identifying an initial set of documents from the search index based on the one or more atoms identified in the reformulated search query; computing preliminary scores for each document in the initial set of documents using both a simplified scoring function and pre-computed scores stored in the search index for document/atom pairs for the one or more atoms and the initial set of documents, wherein a pre-computed score for each document/atom pair represents the importance of an atom extracted from the document, and wherein the simplified scoring function is derived at least in part from ranking features of a full ranking algorithm; selecting a pruned set of documents from the initial set of documents based on the preliminary scores; computing a ranking score for each document in the pruned set of documents using the full ranking algorithm different from the simplified scoring function to provide a set of ranked documents; and providing search results for presentation to an end user based on the set of ranked documents.
1. One or more tangible computer storage media storing computer-useable instructions that, when used by a computing device, cause the computing device to perform a method comprising: receiving a search query; reformulating the search query to identify one or more atoms used to query a search index, the search index storing a plurality of atoms, the plurality of atoms comprising one or more n-grams, one or more n-tuples, and one or more near n-tuples; identifying an initial set of documents from the search index based on the one or more atoms identified in the reformulated search query; computing preliminary scores for each document in the initial set of documents using both a simplified scoring function and pre-computed scores stored in the search index for document/atom pairs for the one or more atoms and the initial set of documents, wherein a pre-computed score for each document/atom pair represents the importance of an atom extracted from the document, and wherein the simplified scoring function is derived at least in part from ranking features of a full ranking algorithm; selecting a pruned set of documents from the initial set of documents based on the preliminary scores; computing a ranking score for each document in the pruned set of documents using the full ranking algorithm different from the simplified scoring function to provide a set of ranked documents; and providing search results for presentation to an end user based on the set of ranked documents. 9. The one or more computer storage media of claim 1 , wherein the search index includes a reverse index and a forward index, and wherein the initial set of documents are identified using the reverse index, the preliminary scores for the initial set of documents are computed using the reverse index, and the ranking scores for the set of ranked documents are computed using the forward index.