19. A system comprising: memory; one or more processors coupled to the memory and configured to perform operations comprising: ranking indexed queries based on a respective query rank of each indexed query, the query rank calculated based on a frequency of occurrence of the indexed query and a user satisfaction score of the indexed query, the indexed queries including highly-ranked queries and nearby queries that are queries that have a statistically significant probability of being revised to one of the highly-ranked queries, wherein the user satisfaction score of a particular indexed query is determined from estimates of lengths of clicks on search results, wherein the estimates of the lengths of clicks on search results are based on a duration of time from a selection of a search result for the particular indexed query to a subsequent selection of another search result; calculating a respective revision score for each indexed query as a function of a revision probability of a first query and the respective query rank for the particular indexed query, the revision probability based on at least one of a semantic similarity or syntactic similarity between the first query and the particular indexed query; selecting one of the indexed queries as an alternative query to the first query based on the respective revision score of the selected indexed query; and providing the selected query as a suggested revision for the first query.
19. A system comprising: memory; one or more processors coupled to the memory and configured to perform operations comprising: ranking indexed queries based on a respective query rank of each indexed query, the query rank calculated based on a frequency of occurrence of the indexed query and a user satisfaction score of the indexed query, the indexed queries including highly-ranked queries and nearby queries that are queries that have a statistically significant probability of being revised to one of the highly-ranked queries, wherein the user satisfaction score of a particular indexed query is determined from estimates of lengths of clicks on search results, wherein the estimates of the lengths of clicks on search results are based on a duration of time from a selection of a search result for the particular indexed query to a subsequent selection of another search result; calculating a respective revision score for each indexed query as a function of a revision probability of a first query and the respective query rank for the particular indexed query, the revision probability based on at least one of a semantic similarity or syntactic similarity between the first query and the particular indexed query; selecting one of the indexed queries as an alternative query to the first query based on the respective revision score of the selected indexed query; and providing the selected query as a suggested revision for the first query. 21. The system of claim 19 in which the function is a product of the revision probability for the first query with respect to the particular indexed query and the query rank for the particular indexed query.