1. A computer-implemented method, comprising: receiving, by a computer system, a search request including a keyword; hashing, by the computer system, the keyword with a plurality of hash functions to obtain a sequence of hash values; using, by the computer system, the hash values to locate a chain of search indices that are stored across a plurality of storage locations, with each search index providing a reference to a storage location of the next search index in the chain; determining, by the computer system, from a hash value in the sequence and a search index in the chain, identifiers of documents that contain the keyword; and returning, by the computer system, a search result containing the identifiers.