8. A computer program product, encoded on one or more non-transitory computer storage media, comprising instructions that when executed by one or more computers cause the one or more computers to perform operations comprising: receiving, at a search system from a user device associated with a user, user input comprising one or more characters of a partial search query; determining that the one or more characters of the partial search query correspond to a trigger query; in response to determining that the one or more characters of the partial search query correspond to a trigger query, determining a predicted query for the trigger query, the predicted query comprising the trigger query and additional information for refining the trigger query; and providing the predicted query to the user device for presentation to the user prior to the user submitting a search query to the search system.
8. A computer program product, encoded on one or more non-transitory computer storage media, comprising instructions that when executed by one or more computers cause the one or more computers to perform operations comprising: receiving, at a search system from a user device associated with a user, user input comprising one or more characters of a partial search query; determining that the one or more characters of the partial search query correspond to a trigger query; in response to determining that the one or more characters of the partial search query correspond to a trigger query, determining a predicted query for the trigger query, the predicted query comprising the trigger query and additional information for refining the trigger query; and providing the predicted query to the user device for presentation to the user prior to the user submitting a search query to the search system. 9. The computer program product of claim 8 , wherein determining that one or more characters of the partial search query correspond to a trigger query comprises: determining, for each query matching the one or more characters of the partial search query in a collection of queries, a respective probability of a plurality of users selecting local search results provided in response to the query; and determining that a query matching the one or more characters of the partial search query in the collection of queries has a probability that satisfies a threshold.