Add embedding cache

crates/meilisearch/src/search/mod.rs

@@ -916,7 +916,7 @@ fn prepare_search<'t>(
                     let deadline = std::time::Instant::now() + std::time::Duration::from_secs(10);
 
                     embedder
-                        .embed_search(query.q.clone().unwrap(), Some(deadline))
+                        .embed_search(query.q.as_ref().unwrap(), Some(deadline))
                         .map_err(milli::vector::Error::from)
                         .map_err(milli::Error::from)?
                 }

crates/milli/src/search/hybrid.rs

@@ -203,7 +203,7 @@ impl<'a> Search<'a> {
 
                 let deadline = std::time::Instant::now() + std::time::Duration::from_secs(3);
 
-                match embedder.embed_search(query, Some(deadline)) {
+                match embedder.embed_search(&query, Some(deadline)) {
                     Ok(embedding) => embedding,
                     Err(error) => {
                         tracing::error!(error=%error, "Embedding failed");

crates/milli/src/vector/composite.rs

@@ -4,7 +4,8 @@ use arroy::Distance;
 
 use super::error::CompositeEmbedderContainsHuggingFace;
 use super::{
-    hf, manual, ollama, openai, rest, DistributionShift, EmbedError, Embedding, NewEmbedderError,
+    hf, manual, ollama, openai, rest, DistributionShift, EmbedError, Embedding, EmbeddingCache,
+    NewEmbedderError,
 };
 use crate::ThreadPoolNoAbort;
 
@@ -148,6 +149,27 @@ impl SubEmbedder {
         }
     }
 
+    pub fn embed_one(
+        &self,
+        text: &str,
+        deadline: Option<Instant>,
+    ) -> std::result::Result<Embedding, EmbedError> {
+        match self {
+            SubEmbedder::HuggingFace(embedder) => embedder.embed_one(text),
+            SubEmbedder::OpenAi(embedder) => {
+                embedder.embed(&[text], deadline)?.pop().ok_or_else(EmbedError::missing_embedding)
+            }
+            SubEmbedder::Ollama(embedder) => {
+                embedder.embed(&[text], deadline)?.pop().ok_or_else(EmbedError::missing_embedding)
+            }
+            SubEmbedder::UserProvided(embedder) => embedder.embed_one(text),
+            SubEmbedder::Rest(embedder) => embedder
+                .embed_ref(&[text], deadline)?
+                .pop()
+                .ok_or_else(EmbedError::missing_embedding),
+        }
+    }
+
     /// Embed multiple chunks of texts.
     ///
     /// Each chunk is composed of one or multiple texts.
@@ -233,6 +255,16 @@ impl SubEmbedder {
             SubEmbedder::Rest(embedder) => embedder.distribution(),
         }
     }
+
+    pub(super) fn cache(&self) -> Option<&EmbeddingCache> {
+        match self {
+            SubEmbedder::HuggingFace(embedder) => Some(embedder.cache()),
+            SubEmbedder::OpenAi(embedder) => Some(embedder.cache()),
+            SubEmbedder::UserProvided(_) => None,
+            SubEmbedder::Ollama(embedder) => Some(embedder.cache()),
+            SubEmbedder::Rest(embedder) => Some(embedder.cache()),
+        }
+    }
 }
 
 fn check_similarity(

crates/milli/src/vector/hf.rs

@@ -7,7 +7,7 @@ use hf_hub::{Repo, RepoType};
 use tokenizers::{PaddingParams, Tokenizer};
 
 pub use super::error::{EmbedError, Error, NewEmbedderError};
-use super::{DistributionShift, Embedding};
+use super::{DistributionShift, Embedding, EmbeddingCache};
 
 #[derive(
     Debug,
@@ -84,6 +84,7 @@ pub struct Embedder {
     options: EmbedderOptions,
     dimensions: usize,
     pooling: Pooling,
+    cache: EmbeddingCache,
 }
 
 impl std::fmt::Debug for Embedder {
@@ -245,7 +246,14 @@ impl Embedder {
             tokenizer.with_padding(Some(pp));
         }
 
-        let mut this = Self { model, tokenizer, options, dimensions: 0, pooling };
+        let mut this = Self {
+            model,
+            tokenizer,
+            options,
+            dimensions: 0,
+            pooling,
+            cache: EmbeddingCache::new(super::CAP_PER_THREAD),
+        };
 
         let embeddings = this
             .embed(vec!["test".into()])
@@ -355,4 +363,8 @@ impl Embedder {
     pub(crate) fn embed_index_ref(&self, texts: &[&str]) -> Result<Vec<Embedding>, EmbedError> {
         texts.iter().map(|text| self.embed_one(text)).collect()
     }
+
+    pub(super) fn cache(&self) -> &EmbeddingCache {
+        &self.cache
+    }
 }

crates/milli/src/vector/mod.rs

@@ -1,4 +1,6 @@
+use std::cell::RefCell;
 use std::collections::HashMap;
+use std::num::{NonZeroUsize, TryFromIntError};
 use std::sync::Arc;
 use std::time::Instant;
 
@@ -551,6 +553,51 @@ pub enum Embedder {
     Composite(composite::Embedder),
 }
 
+#[derive(Debug)]
+struct EmbeddingCache {
+    data: thread_local::ThreadLocal<RefCell<lru::LruCache<String, Embedding>>>,
+    cap_per_thread: u16,
+}
+
+impl EmbeddingCache {
+    pub fn new(cap_per_thread: u16) -> Self {
+        Self { cap_per_thread, data: thread_local::ThreadLocal::new() }
+    }
+
+    /// Get the embedding corresponding to `text`, if any is present in the cache.
+    pub fn get(&self, text: &str) -> Option<Embedding> {
+        let mut cache = self
+            .data
+            .get_or_try(|| -> Result<RefCell<lru::LruCache<String, Vec<f32>>>, TryFromIntError> {
+                Ok(RefCell::new(lru::LruCache::new(NonZeroUsize::try_from(
+                    self.cap_per_thread as usize,
+                )?)))
+            })
+            .ok()?
+            .borrow_mut();
+
+        cache.get(text).cloned()
+    }
+
+    /// Puts a new embedding for the specified `text`
+    pub fn put(&self, text: String, embedding: Embedding) {
+        let Ok(cache) = self.data.get_or_try(
+            || -> Result<RefCell<lru::LruCache<String, Vec<f32>>>, TryFromIntError> {
+                Ok(RefCell::new(lru::LruCache::new(NonZeroUsize::try_from(
+                    self.cap_per_thread as usize,
+                )?)))
+            },
+        ) else {
+            return;
+        };
+        let mut cache = cache.borrow_mut();
+
+        cache.put(text, embedding);
+    }
+}
+
+pub const CAP_PER_THREAD: u16 = 20;
+
 /// Configuration for an embedder.
 #[derive(Debug, Clone, Default, serde::Deserialize, serde::Serialize)]
 pub struct EmbeddingConfig {
@@ -651,19 +698,36 @@ impl Embedder {
     #[tracing::instrument(level = "debug", skip_all, target = "search")]
     pub fn embed_search(
         &self,
-        text: String,
+        text: &str,
         deadline: Option<Instant>,
     ) -> std::result::Result<Embedding, EmbedError> {
-        let texts = vec![text];
-        let mut embedding = match self {
-            Embedder::HuggingFace(embedder) => embedder.embed(texts),
-            Embedder::OpenAi(embedder) => embedder.embed(&texts, deadline),
-            Embedder::Ollama(embedder) => embedder.embed(&texts, deadline),
-            Embedder::UserProvided(embedder) => embedder.embed(&texts),
-            Embedder::Rest(embedder) => embedder.embed(texts, deadline),
-            Embedder::Composite(embedder) => embedder.search.embed(texts, deadline),
+        if let Some(cache) = self.cache() {
+            if let Some(embedding) = cache.get(text) {
+                tracing::trace!(text, "embedding found in cache");
+                return Ok(embedding);
+            }
+        }
+        let embedding = match self {
+            Embedder::HuggingFace(embedder) => embedder.embed_one(text),
+            Embedder::OpenAi(embedder) => {
+                embedder.embed(&[text], deadline)?.pop().ok_or_else(EmbedError::missing_embedding)
+            }
+            Embedder::Ollama(embedder) => {
+                embedder.embed(&[text], deadline)?.pop().ok_or_else(EmbedError::missing_embedding)
+            }
+            Embedder::UserProvided(embedder) => embedder.embed_one(text),
+            Embedder::Rest(embedder) => embedder
+                .embed_ref(&[text], deadline)?
+                .pop()
+                .ok_or_else(EmbedError::missing_embedding),
+            Embedder::Composite(embedder) => embedder.search.embed_one(text, deadline),
         }?;
-        let embedding = embedding.pop().ok_or_else(EmbedError::missing_embedding)?;
+
+        if let Some(cache) = self.cache() {
+            tracing::trace!(text, "embedding added to cache");
+            cache.put(text.to_owned(), embedding.clone());
+        }
+
         Ok(embedding)
     }
 
@@ -759,6 +823,17 @@ impl Embedder {
             Embedder::Composite(embedder) => embedder.index.uses_document_template(),
         }
     }
+
+    fn cache(&self) -> Option<&EmbeddingCache> {
+        match self {
+            Embedder::HuggingFace(embedder) => Some(embedder.cache()),
+            Embedder::OpenAi(embedder) => Some(embedder.cache()),
+            Embedder::UserProvided(_) => None,
+            Embedder::Ollama(embedder) => Some(embedder.cache()),
+            Embedder::Rest(embedder) => Some(embedder.cache()),
+            Embedder::Composite(embedder) => embedder.search.cache(),
+        }
+    }
 }
 
 /// Describes the mean and sigma of distribution of embedding similarity in the embedding space.

crates/milli/src/vector/ollama.rs

@@ -5,7 +5,7 @@ use rayon::slice::ParallelSlice as _;
 
 use super::error::{EmbedError, EmbedErrorKind, NewEmbedderError, NewEmbedderErrorKind};
 use super::rest::{Embedder as RestEmbedder, EmbedderOptions as RestEmbedderOptions};
-use super::{DistributionShift, REQUEST_PARALLELISM};
+use super::{DistributionShift, EmbeddingCache, REQUEST_PARALLELISM};
 use crate::error::FaultSource;
 use crate::vector::Embedding;
 use crate::ThreadPoolNoAbort;
@@ -182,6 +182,10 @@ impl Embedder {
     pub fn distribution(&self) -> Option<DistributionShift> {
         self.rest_embedder.distribution()
     }
+
+    pub(super) fn cache(&self) -> &EmbeddingCache {
+        self.rest_embedder.cache()
+    }
 }
 
 fn get_ollama_path() -> String {

crates/milli/src/vector/openai.rs

@@ -7,7 +7,7 @@ use rayon::slice::ParallelSlice as _;
 
 use super::error::{EmbedError, NewEmbedderError};
 use super::rest::{Embedder as RestEmbedder, EmbedderOptions as RestEmbedderOptions};
-use super::{DistributionShift, REQUEST_PARALLELISM};
+use super::{DistributionShift, EmbeddingCache, REQUEST_PARALLELISM};
 use crate::error::FaultSource;
 use crate::vector::error::EmbedErrorKind;
 use crate::vector::Embedding;
@@ -318,6 +318,10 @@ impl Embedder {
     pub fn distribution(&self) -> Option<DistributionShift> {
         self.options.distribution()
     }
+
+    pub(super) fn cache(&self) -> &EmbeddingCache {
+        self.rest_embedder.cache()
+    }
 }
 
 impl fmt::Debug for Embedder {

crates/milli/src/vector/rest.rs

@@ -9,7 +9,10 @@ use serde::{Deserialize, Serialize};
 
 use super::error::EmbedErrorKind;
 use super::json_template::ValueTemplate;
-use super::{DistributionShift, EmbedError, Embedding, NewEmbedderError, REQUEST_PARALLELISM};
+use super::{
+    DistributionShift, EmbedError, Embedding, EmbeddingCache, NewEmbedderError, CAP_PER_THREAD,
+    REQUEST_PARALLELISM,
+};
 use crate::error::FaultSource;
 use crate::ThreadPoolNoAbort;
 
@@ -75,6 +78,7 @@ pub struct Embedder {
     data: EmbedderData,
     dimensions: usize,
     distribution: Option<DistributionShift>,
+    cache: EmbeddingCache,
 }
 
 /// All data needed to perform requests and parse responses
@@ -152,7 +156,12 @@ impl Embedder {
             infer_dimensions(&data)?
         };
 
-        Ok(Self { data, dimensions, distribution: options.distribution })
+        Ok(Self {
+            data,
+            dimensions,
+            distribution: options.distribution,
+            cache: EmbeddingCache::new(CAP_PER_THREAD),
+        })
     }
 
     pub fn embed(
@@ -256,6 +265,10 @@ impl Embedder {
     pub fn distribution(&self) -> Option<DistributionShift> {
         self.distribution
     }
+
+    pub(super) fn cache(&self) -> &EmbeddingCache {
+        &self.cache
+    }
 }
 
 fn infer_dimensions(data: &EmbedderData) -> Result<usize, NewEmbedderError> {