38. The method of claim 31 , wherein the plurality of index servers are configured to perform query intersections among the documents identified by the shards of the first and second posting lists.
31. A method of indexing documents of a document collection in an indexing system that includes a plurality of index servers, the method comprising: determining a phrase posting list associated with a first phrase, the phrase posting list identifying documents of the document collection associated with the first phrase; dividing the phrase posting list for the first phrase into a plurality of different shards, each shard identifying a subset of the documents identified by the posting list; storing each different shard of the phrase posting list for the first phrase on a corresponding different index server; determining a phrase posting list associated with a second phrase, the phrase posting list identifying a number of documents of the document collection having at least one occurrence of the second phrase; dividing the phrase posting list for the second phrase into a plurality of different shards, each shard identifying a subset of the plurality of the documents identified by the posting list; and storing each different shard of the phrase posting list for the second phrase on a corresponding different index server, wherein shards of the phrase posting list for the first phrase and shards of the phrase posting list for the second phrase, which identify the same document, are stored on the same index server.