10. A system comprising: one or more computers comprising one or more processors programmed to perform operations comprising: receiving a plurality of search results responsive to a query, wherein the query includes one or more words, wherein each search result identifies a respective document that comprises a plurality of segments, wherein each segment is a distinct sequence of consecutive characters in the respective document; identifying the plurality of segments for each document by sliding a fixed-length window over content of the document, wherein the content of the document encompassed by the window starting at a particular position in the document defines a particular segment in the document, wherein sliding the fixed-length window over the content of the document comprises skipping space characters and characters that would result in a last character of the window splitting a word; for each of the plurality of segments in each of the documents, determining a respective count of occurrences of the one or more words of the query that occur in the segment; for each of the documents, ranking the segments of the document based on the respective counts of the segments; and identifying one or more highest ranked segments for each of the documents as a query-relevant part of the document.
11. The system of claim 10 , wherein the operations further comprise sending the search results that identify the documents and the query-relevant parts of the documents to a computing device in a response to the query.