7. The method of claim 1 , further comprising: 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.
1. 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; storing a plurality of shards of different phrase posting lists on a first index server; storing a plurality of shards of different phrase posting lists on a second index server; and within each of the first and second index servers, for each shard of a phrase posting list, ordering the shard according to document identifiers of the documents included in the shard.