Multi-layer search-engine index

A system for indexing a document in a search-engine index, the system comprising:

• a hardware processor and a memory configured for providing computer program instructions to the processor;
• a search engine configured to:
• assign a document identifier to the document;
• determine 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;
• encode 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
• store 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 a search query.

A system that includes a processor coupled with a computer storage device and that indexes a document in a search-engine index, the system comprising:

• a term index maintained as part of the search-engine index, the term index including a plurality of term postings each of which stores information relevant to a respective term,
• wherein the information relevant to the respective term includes a document identifier that identifies a document that includes the respective term and a frequency with which the term is included among content of the document, and
• wherein the document identifier is encoded together with the frequency when stored in the term index, such that the document identifier and the frequency are interleaving;
• and
• a per-document index that stores a set of document-ranking information and that is separate from the term index, wherein the document-ranking information is used to rank the respective document when processing a search query.