6. The method of claim 1 , wherein the set of document-ranking information includes a list of searchable terms that are included among content of the document, and wherein each searchable term included on the list of searchable terms is encoded by assigning each searchable term a respective pre-determined global term identifier, which is used to identify each searchable term throughout the per-document index.
1. A method of indexing a document in a search-engine index to allow a search engine to assess a relevance of the document to a search query, the method comprising: assigning a document identifier to the document; determining a frequency with which a term is included among content of the document, wherein the search-engine index comprises a term index, which includes a term posting having information relevant to the term; encoding the document identifier together with the frequency to generate encoded document information, wherein the term posting is transformed to include the encoded document information; and storing a set of document-ranking information in a per-document index, which is separate from the term index, wherein the document-ranking information is used to rank the document when processing the search query.