La recherche à l’ère de l’IA

A presentation at Alpes JUG in May 2024 in Grenoble, France by David Pilato

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Search & AI a new era : David Pilato | @dadoonet

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Agenda ● ● ● ● Co m m er ci “Classic” search and its limitations ML model and usage Vector search or hybrid search in Elasticsearch OpenAI’s ChatGPT or LLMs with Elasticsearch al

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Elasticsearch You Know, for Search

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These are not the droids you are looking for.

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GET /_analyze { “char_filter”: [ “html_strip” ], “tokenizer”: “standard”, “filter”: [ “lowercase”, “stop”, “snowball” ], “text”: “These are <em>not</em> the droids you are looking for.” }

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These are <em>not</em> the droids you are looking for. { “tokens”: [{ “token”: “droid”, “start_offset”: 27, “end_offset”: 33, “type”: “<ALPHANUM>”, “position”: 4 },{ “token”: “you”, “start_offset”: 34, “end_offset”: 37, “type”: “<ALPHANUM>”, “position”: 5 }, { “token”: “look”, “start_offset”: 42, “end_offset”: 49, “type”: “<ALPHANUM>”, “position”: 7 }]}

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Semantic search ≠ Literal matches

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TODAY X-wing starfighter squadron TOMORROW What ships and crews do I need to destroy an almost finished death star? Or is there a secret weakness?

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Elasticsearch You Know, for Search

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Elasticsearch You Know, for Vector Search

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What is a Vector ?

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Example: 1-dimensional vector Character Vector [ 1 ] ] Realistic

[ Embeddings represent your data Cartoon 1

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represent different data aspects Human Character Vector [ 1, 1 Realistic Cartoon ] ] Machine

[ Multiple dimensions 1, 0

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is grouped together Human Character Vector [ 1.0, 1.0 Realistic Cartoon 1.0, 0.0 [ 1.0, 0.8 ] ] ]

Machine

[ Similar data

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Vector search ranks objects by similarity (~relevance) to the query Human Rank Query 1 Realistic Cartoon 2 3 4 5 Machine Result

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Choice of Embedding Model Start with Off-the Shelf Models Extend to Higher Relevance ●Text data: Hugging Face (like Microsoft’s E5 ●Apply hybrid scoring ) ●Images: OpenAI’s CLIP ●Bring Your Own Model: requires expertise + labeled data

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Problem training vs actual use-case

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Architecture of Vector Search

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How do you index vectors ?

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Data Ingestion and Embedding Generation POST /_doc { “_id”:”product-1234”, “product_name”:”Summer Dress”, “description”:”Our best-selling…”, “Price”: 118, “color”:”blue”, “fabric”:”cotton”, “fabric”:”cotton” } “desc_embedding”:[0.452,0.3242,…], “desc_embedding”:[0.452,0.3242,…] } “img_embedding”:[0.012,0.0,…] } Source data POST /_doc

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Co m m er ci With Elastic ML al { } Source data POST /_doc “_id”:”product-1234”, “product_name”:”Summer Dress”, “description”:”Our best-selling…”, “Price”: 118, “color”:”blue”, “fabric”:”cotton”, “desc_embedding”:[0.452,0.3242,…]

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Eland Imports PyTorch Models Co m m er ci al $ eland_import_hub_model —url https://cluster_URL —hubmodel-id BERT-MiniLM-L6 —tasktype text_embedding —start BERT-MiniLM-L6 Select the appropriate model Load it Manage models

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Elastic’s range of supported NLP models Co m m er ci ● Fill mask model Mask some of the words in a sentence and predict words that replace masks ● Named entity recognition model NLP method that extracts information from text ● Text embedding model Represent individual words as numerical vectors in a predefined vector space ● Text classification model Assign a set of predefined categories to open-ended text ● Question answering model Model that can answer questions given some or no context ● Zero-shot text classification model Model trained on a set of labeled examples, that is able to classify previously unseen examples Full list at: ela.st/nlp-supported-models al

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How do you search vectors ?

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Vector Query GET product-catalog/_search { “query” : { “bool”: { “must”: [{ “knn”: { “field”: “desc_embbeding”, “num_candidates”: 50, “query_vector”: [0.123, 0.244,…] } }], “filter”: { “term”: { “department”: “women” } } } } }, “size”: 10

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Vector Query Transformer model Co m m er ci al GET product-catalog/_search { “query” : { “bool”: { “must”: [{ “knn”: { “field”: “desc_embbeding”, “num_candidates”: 50, “query_vector_builder”: { “text_embedding”: { “model_text”: “summer clothes”, “model_id”: <text-embedding-model> } } } }], “filter”: { “term”: { “department”: “women” } } } }, “size”: 10 }

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( Vector Search components Search Index Generate Query Mapping Embedding dense_vector Text embedding model kNN 3rd party, local, in Elasticsearch)

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But how does it really work?

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Similarity: cosine (cosine) Human q cos(θ) = d1 d2 Realistic θ q⃗ × d ⃗ | q⃗ | × | d |⃗ _score = 1 + cos(θ) 2

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Similarity: cosine (cosine) 1+1 _score = =1 2 1+0 _score = = 0.5 2 1−1 _score = =0 2

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Similarity: Dot Product (dot_product) q⃗ × d ⃗ = | q⃗ | × cos(θ) × | d |⃗ q d θ | q⃗ | × co s (θ ) 1 + dot_ product(q, d) scorefloat = 2 0.5 + dot product(q, d) _scorebyte = 32768 × dims

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Similarity: Euclidean distance (l2_norm) y 2 n i (x ∑ 1 i= − y i) q l2_normq,d = y1 d x1 y2 x2 n ∑ i=1 (xi − yi) 1 _score = 1 + (l2_normq,d )2 x 2

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Brute Force

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Hierarchical Navigable Small Worlds (HNSW One popular approach HNSW: a layered approach that simplifies access to the nearest neighbor Tiered: from coarse to fine approximation over a few steps Balance: Bartering a little accuracy for a lot of scalability ) Speed: Excellent query latency on large scale indices

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Filtering KNN Vector Similarity Automatically choose between brute force and HNSW Brute force (not real numbers; used only to demonstrate the linearity) HNSW fi Bound worst case to 2*(brute force) • Brute force scales O(n) of ltered • HNSW scales ~O(log(n)) of all docs

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Elasticsearch + Lucene = fast progress ❤

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Scaling Vector Search Vector search Best practices

  1. Needs lots of memory
  2. Avoid searches during indexing
  3. Indexing is slower
  4. Exclude vectors from _source
  5. Merging is slow
  6. Reduce vector dimensionality 4. Use byte rather than float
  • Continuous improvements in Lucene + Elasticsearch

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Reduce Required Memory 2. Reduce of number of dimensions per vector

  1. Vector element size reduction (“quantize”)

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Benchmarketing

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https://github.com/erikbern/ann-benchmarks

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Elasticsearch You Know, for Hybrid Search

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Hybrid scoring Term-based score Linear Combination manual boosting Vector similarity score Combine

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GET product-catalog/_search { “query” : { “bool” : { “must” : [{ “match”: { “description”: { “query”: “summer clothes”, “boost”: 0.9 } } },{ “knn”: { “field”: “desc_embbeding”, “query_vector”: [0.123, 0.244,…], “num_candidates”: 50, “boost”: 0.1, “filter”: { “term”: { “department”: “women” } } } }], “filter” : { “range” : { “price”: { “lte”: 30 } } } } } } summer clothes pre-filter post-filter

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GET product-catalog/_search { “query” : { “bool” : { “must” : [{ “match”: { “description”: { “query”: “summer clothes”, “boost”: 0.9 } } },{ “knn”: { “field”: “image-vector”, “query_vector”: [54, 10, -2], “num_candidates”: 50, “boost”: 0.1 } },{ “knn”: { “field”: “title-vector”, “query_vector”: [1, 20, -52, 23, 10], “num_candidates”: 10, “boost”: 0.5 } }] } } }

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ELSER Elastic Learned Sparse EncodER text_expansion Not BM25 or (dense) vector Sparse vector like BM25 Stored as inverted index Co m m er ci al

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PUT /_inference/sparse_embedding/my_elser_model { “service”: “elser”, “service_settings”: { “num_allocations”: 1, “num_threads”: 1 }, “task_settings”: {} } PUT /_inference/text_embedding/openai_embeddings { “service”: “openai”, “service_settings”: { “api_key”: “<api_key>” }, “task_settings”: { “model”: “text-embedding-ada-002” } } PUT /_inference/text_embedding/hugging_face_embeddings { “service”: “hugging_face”, “service_settings”: { “api_key”: “<access_token>”, “url”: “<url_endpoint>” } } Co m m er ci al

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POST /_inference/sparse_embedding/my_elser_model { “input”: [ “These are not the droids you are looking for.”, } ] “Obi-Wan never told you what happened to your father.” { “sparse_embedding”: [{ “lucas”: 0.50047517, “ship”: 0.29860738, “dragon”: 0.5300422, “quest”: 0.5974301, “dr”: 2.1055143, “space”: 0.49377063, “robot”: 0.40398192, … Co m m er ci al

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Co m m er ci Hybrid ranking al Vector similarity score Reciprocal Rank Fusion (RRF blend multiple ranking methods Combine ) Term-based score ELSER score

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GET product-catalog/_search { “sub_searches”: [ { “query”: { “match”: {…} } }, { “query”: { “text_expansion”: {…} } } ], “knn”: {…}, “rank”: { “rrf”: { “window_size”: 50, “rank_constant”: 20 } } } Co m m er ci al BM25f + ELSER + Vector Hybrid Ranking

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Reciprocal Rank Fusion (RRF D set of docs R set of rankings as permutation on 1..|D| k - typically set to 60 by default Ranking Algorithm 1 r(d) k+r(d) A 1 1 B 0.7 C D Score r(d) k+r(d) 61 C 1,341 1 61 2 62 A 739 2 62 0.5 3 63 F 732 3 63 0.2 4 64 G 192 4 64 0.01

=

= +

E Doc 5 65 H 183 5 65 ) Score

Doc Ranking Algorithm 2 Doc RRF Score A 1/61 1/62 0,0325 C 1/63 1/61 0,0323 B 1/62 0,0161 F 1/63 0,0159 D 1/64 0,0156

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https://djdadoo.pilato.fr/

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https://github.com/dadoonet/music-search/

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ChatGPT Elastic and LLM

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Gen AI Search engines

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LLM opportunities and limits your question one answer your question GAI / LLM : public internet data

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Retrieval Augmented Generation your question the right answer your question + context window GAI / LLM public internet data your business data documents images audio

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Demo Elastic + Azure OpenAI AWS Bedrock Google Vertex AI

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Peut-être remplacée par votre propre source de données

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Conclusion

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( Vector Database Hybrid Search (text + vector) Vector Database + ML Semantic) Search Engine Store & Search Vector Embeddings Choice & Flexibility of embedding models Filtering & Faceting Create Vector Embeddings Aggregations Autocomplete Search Analytics Trained model outof-the-box Document-level Security Optimized for text, geo, & other data Ingest Tools (web crawler, connectors, Beats, Agent, API framework) On-prem / Cloud / Hybrid

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Elasticsearch You Know, for Semantic Search

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Search & AI a new era : David Pilato | @dadoonet