8. A non-transitory computer-readable medium storing instructions, the instructions comprising: one or more instructions which, when executed by one or more processors, cause the one or more processors to determine information identifying a measure of quality of each document, of a plurality of documents, as a search result for one or more search queries, the information, identifying the measure of quality of a particular document in the plurality of documents, being determined based on: a probability that the particular document will be selected at least a threshold number of times during a particular time period when the particular document is presented as a search result, and a probability that the particular document will be presented as a search result at least a threshold number of times during a particular time period; one or more instructions which, when executed by the one or more processors, cause the one or more processors to select one or more documents of the plurality of documents, each document, of the one or more documents, being selected based on the measure of quality of the document; one or more instructions which, when executed by the one or more processors, cause the one or more processors to store, in an index, information regarding the one or more documents, the information regarding the one or more documents being stored in the index based on the measure of quality of each document of the one or more documents; one or more instructions which, when executed by the one or more processors, cause the one or more processors to predict, based on the information identifying the measure of quality of each document of the one or more documents, a measure of quality of at least one other document as a search result for a particular search query; and one or more instructions which, when executed by the one or more processors, cause the one or more processors to determine whether to store, in the index, information regarding the at least one other document based on the measure of quality of the at least one other document.
8. A non-transitory computer-readable medium storing instructions, the instructions comprising: one or more instructions which, when executed by one or more processors, cause the one or more processors to determine information identifying a measure of quality of each document, of a plurality of documents, as a search result for one or more search queries, the information, identifying the measure of quality of a particular document in the plurality of documents, being determined based on: a probability that the particular document will be selected at least a threshold number of times during a particular time period when the particular document is presented as a search result, and a probability that the particular document will be presented as a search result at least a threshold number of times during a particular time period; one or more instructions which, when executed by the one or more processors, cause the one or more processors to select one or more documents of the plurality of documents, each document, of the one or more documents, being selected based on the measure of quality of the document; one or more instructions which, when executed by the one or more processors, cause the one or more processors to store, in an index, information regarding the one or more documents, the information regarding the one or more documents being stored in the index based on the measure of quality of each document of the one or more documents; one or more instructions which, when executed by the one or more processors, cause the one or more processors to predict, based on the information identifying the measure of quality of each document of the one or more documents, a measure of quality of at least one other document as a search result for a particular search query; and one or more instructions which, when executed by the one or more processors, cause the one or more processors to determine whether to store, in the index, information regarding the at least one other document based on the measure of quality of the at least one other document. 10. The non-transitory computer-readable medium of claim 8 , where the one or more instructions to determine the information identifying the measure of quality of the particular document include: one or more instructions which, when executed by the one or more processors, cause the one or more processors to determine the information identifying the measure of quality of the particular document further based on rules generated, for a model, based on a plurality of search queries and corresponding search results.