Benjamin Trent 5add44d7d1 Adds new bit element_type for dense_vectors (#110059) ... This commit adds `bit` vector support by adding `element_type: bit` for vectors. This new element type works for indexed and non-indexed vectors. Additionally, it works with `hnsw` and `flat` index types. No quantization based codec works with this element type, this is consistent with `byte` vectors. `bit` vectors accept up to `32768` dimensions in size and expect vectors that are being indexed to be encoded either as a hexidecimal string or a `byte[]` array where each element of the `byte` array represents `8` bits of the vector. `bit` vectors support script usage and regular query usage. When indexed, all comparisons done are `xor` and `popcount` summations (aka, hamming distance), and the scores are transformed and normalized given the vector dimensions. Note, indexed bit vectors require `l2_norm` to be the similarity. For scripts, `l1norm` is the same as `hamming` distance and `l2norm` is `sqrt(l1norm)`. `dotProduct` and `cosineSimilarity` are not supported. Note, the dimensions expected by this element_type are always to be divisible by `8`, and the `byte[]` vectors provided for index must be have size `dim/8` size, where each byte element represents `8` bits of the vectors. closes: https://github.com/elastic/elasticsearch/issues/48322		2024-06-27 04:48:41 +10:00
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vector-functions.asciidoc	Adds new bit element_type for dense_vectors (#110059)	2024-06-27 04:48:41 +10:00