7. One or more computer storage media having stored thereon a data structure for storing data representing a forward index that is used to rank search results based on a search query, the data structure comprising: a first data field containing document identification information that identifies a particular document; a second data field containing a compressed token stream of the document, wherein the compressed token stream is a second token stream based on a first token stream, the compressed token stream is a compressed version of the token stream comprising context streams of the document selected from the first token stream, wherein the one or more context streams represent individual portions of the document; a third data field containing document-specific data representing static features of the document that are used to rank the document when a query is received; and a fourth data field containing positional information that indicates the position of one or more relevant data associated with the document that is frequently used to calculate a ranking of the document.
7. One or more computer storage media having stored thereon a data structure for storing data representing a forward index that is used to rank search results based on a search query, the data structure comprising: a first data field containing document identification information that identifies a particular document; a second data field containing a compressed token stream of the document, wherein the compressed token stream is a second token stream based on a first token stream, the compressed token stream is a compressed version of the token stream comprising context streams of the document selected from the first token stream, wherein the one or more context streams represent individual portions of the document; a third data field containing document-specific data representing static features of the document that are used to rank the document when a query is received; and a fourth data field containing positional information that indicates the position of one or more relevant data associated with the document that is frequently used to calculate a ranking of the document. 10. The one or more computer storage media of claim 7 , wherein the second data field further contains separate token streams of one or more portions of the document.