Store the vectors in an HNSW in LMDB

milli/src/index.rs

@@ -8,10 +8,12 @@ use charabia::{Language, Script};
 use heed::flags::Flags;
 use heed::types::*;
 use heed::{CompactionOption, Database, PolyDatabase, RoTxn, RwTxn};
+use rand_pcg::Pcg32;
 use roaring::RoaringBitmap;
 use rstar::RTree;
 use time::OffsetDateTime;
 
+use crate::dot_product::DotProduct;
 use crate::error::{InternalError, UserError};
 use crate::facet::FacetType;
 use crate::fields_ids_map::FieldsIdsMap;
@@ -26,6 +28,9 @@ use crate::{
     Result, RoaringBitmapCodec, RoaringBitmapLenCodec, Search, U8StrStrCodec, BEU16, BEU32,
 };
 
+/// The HNSW data-structure that we serialize, fill and search in.
+pub type Hnsw = hnsw::Hnsw<DotProduct, Vec<f32>, Pcg32, 12, 24>;
+
 pub const DEFAULT_MIN_WORD_LEN_ONE_TYPO: u8 = 5;
 pub const DEFAULT_MIN_WORD_LEN_TWO_TYPOS: u8 = 9;
 
@@ -42,6 +47,7 @@ pub mod main_key {
     pub const FIELDS_IDS_MAP_KEY: &str = "fields-ids-map";
     pub const GEO_FACETED_DOCUMENTS_IDS_KEY: &str = "geo-faceted-documents-ids";
     pub const GEO_RTREE_KEY: &str = "geo-rtree";
+    pub const VECTOR_HNSW_KEY: &str = "vector-hnsw";
     pub const HARD_EXTERNAL_DOCUMENTS_IDS_KEY: &str = "hard-external-documents-ids";
     pub const NUMBER_FACETED_DOCUMENTS_IDS_PREFIX: &str = "number-faceted-documents-ids";
     pub const PRIMARY_KEY_KEY: &str = "primary-key";
@@ -86,6 +92,7 @@ pub mod db_name {
     pub const FACET_ID_STRING_DOCIDS: &str = "facet-id-string-docids";
     pub const FIELD_ID_DOCID_FACET_F64S: &str = "field-id-docid-facet-f64s";
     pub const FIELD_ID_DOCID_FACET_STRINGS: &str = "field-id-docid-facet-strings";
+    pub const VECTOR_ID_DOCID: &str = "vector-id-docids";
     pub const DOCUMENTS: &str = "documents";
     pub const SCRIPT_LANGUAGE_DOCIDS: &str = "script_language_docids";
 }
@@ -149,6 +156,9 @@ pub struct Index {
     /// Maps the document id, the facet field id and the strings.
     pub field_id_docid_facet_strings: Database<FieldDocIdFacetStringCodec, Str>,
 
+    /// Maps a vector id to the document id that have it.
+    pub vector_id_docid: Database<OwnedType<BEU32>, OwnedType<BEU32>>,
+
     /// Maps the document id to the document as an obkv store.
     pub(crate) documents: Database<OwnedType<BEU32>, ObkvCodec>,
 }
@@ -162,7 +172,7 @@ impl Index {
     ) -> Result<Index> {
         use db_name::*;
 
-        options.max_dbs(23);
+        options.max_dbs(24);
         unsafe { options.flag(Flags::MdbAlwaysFreePages) };
 
         let env = options.open(path)?;
@@ -198,11 +208,11 @@ impl Index {
             env.create_database(&mut wtxn, Some(FACET_ID_IS_NULL_DOCIDS))?;
         let facet_id_is_empty_docids =
             env.create_database(&mut wtxn, Some(FACET_ID_IS_EMPTY_DOCIDS))?;
-
         let field_id_docid_facet_f64s =
             env.create_database(&mut wtxn, Some(FIELD_ID_DOCID_FACET_F64S))?;
         let field_id_docid_facet_strings =
             env.create_database(&mut wtxn, Some(FIELD_ID_DOCID_FACET_STRINGS))?;
+        let vector_id_docid = env.create_database(&mut wtxn, Some(VECTOR_ID_DOCID))?;
         let documents = env.create_database(&mut wtxn, Some(DOCUMENTS))?;
         wtxn.commit()?;
 
@@ -231,6 +241,7 @@ impl Index {
             facet_id_is_empty_docids,
             field_id_docid_facet_f64s,
             field_id_docid_facet_strings,
+            vector_id_docid,
             documents,
         })
     }
@@ -502,6 +513,26 @@ impl Index {
         }
     }
 
+    /* vector HNSW */
+
+    /// Writes the provided `hnsw`.
+    pub(crate) fn put_vector_hnsw(&self, wtxn: &mut RwTxn, hnsw: &Hnsw) -> heed::Result<()> {
+        self.main.put::<_, Str, SerdeBincode<Hnsw>>(wtxn, main_key::VECTOR_HNSW_KEY, hnsw)
+    }
+
+    /// Delete the `hnsw`.
+    pub(crate) fn delete_vector_hnsw(&self, wtxn: &mut RwTxn) -> heed::Result<bool> {
+        self.main.delete::<_, Str>(wtxn, main_key::VECTOR_HNSW_KEY)
+    }
+
+    /// Returns the `hnsw`.
+    pub fn vector_hnsw(&self, rtxn: &RoTxn) -> Result<Option<Hnsw>> {
+        match self.main.get::<_, Str, SerdeBincode<Hnsw>>(rtxn, main_key::VECTOR_HNSW_KEY)? {
+            Some(hnsw) => Ok(Some(hnsw)),
+            None => Ok(None),
+        }
+    }
+
     /* field distribution */
 
     /// Writes the field distribution which associates every field name with
@@ -1466,9 +1497,9 @@ pub(crate) mod tests {
 
         db_snap!(index, field_distribution,
             @r###"
-        age              1      |
-        id               2      |
-        name             2      |
+        age              1
+        id               2
+        name             2
         "###
         );
 
@@ -1486,9 +1517,9 @@ pub(crate) mod tests {
 
         db_snap!(index, field_distribution,
             @r###"
-        age              1      |
-        id               2      |
-        name             2      |
+        age              1
+        id               2
+        name             2
         "###
         );
 
@@ -1502,9 +1533,9 @@ pub(crate) mod tests {
 
         db_snap!(index, field_distribution,
             @r###"
-        has_dog          1      |
-        id               2      |
-        name             2      |
+        has_dog          1
+        id               2
+        name             2
         "###
         );
     }