7. A computer program product comprising one or more non-transitory computer readable storage media storing instructions translatable by one or more processors to perform: generating content vectors for terms in a data set, wherein the content vectors define a similarity metric; generating index vectors for the terms in the data set from the content vectors to access the terms in the data set; and generating bitset signatures from the index vectors to determine similarity with the terms in the data set, wherein the bitset signatures include a first section for positive magnitude values and a second section for negative magnitude values, and generating the bitset signatures from the index vectors comprises: for each of a predetermined number of highest magnitude positive values in the corresponding index vector, setting a corresponding bitset signature value at a corresponding dimension in the first section to a predetermined value; and for each of a predetermined number of highest magnitude negative values in the corresponding index vector, setting a corresponding bitset signature value at a corresponding dimension in the second section to the predetermined value; storing the bitset signatures and content vectors in an index; and performing a search on each of one or more terms in a search query by: accessing a bitset signature and content vector from the index corresponding to a term in the search query; retrieving bitset signatures from the index that are within a predetermined closeness to the accessed bitset signature; selecting content vectors from the index corresponding to the retrieved bitset signatures; identifying the selected content vectors that are within a predetermined similarity to the accessed content vector corresponding to the term in the search query; and returning the terms of the data set corresponding to the identified content vectors.
7. A computer program product comprising one or more non-transitory computer readable storage media storing instructions translatable by one or more processors to perform: generating content vectors for terms in a data set, wherein the content vectors define a similarity metric; generating index vectors for the terms in the data set from the content vectors to access the terms in the data set; and generating bitset signatures from the index vectors to determine similarity with the terms in the data set, wherein the bitset signatures include a first section for positive magnitude values and a second section for negative magnitude values, and generating the bitset signatures from the index vectors comprises: for each of a predetermined number of highest magnitude positive values in the corresponding index vector, setting a corresponding bitset signature value at a corresponding dimension in the first section to a predetermined value; and for each of a predetermined number of highest magnitude negative values in the corresponding index vector, setting a corresponding bitset signature value at a corresponding dimension in the second section to the predetermined value; storing the bitset signatures and content vectors in an index; and performing a search on each of one or more terms in a search query by: accessing a bitset signature and content vector from the index corresponding to a term in the search query; retrieving bitset signatures from the index that are within a predetermined closeness to the accessed bitset signature; selecting content vectors from the index corresponding to the retrieved bitset signatures; identifying the selected content vectors that are within a predetermined similarity to the accessed content vector corresponding to the term in the search query; and returning the terms of the data set corresponding to the identified content vectors. 10. A computer program product according to claim 7 , wherein the generated index vectors are smaller in dimension than the generated content vectors.