Merge pull request #36 from meilisearch/index-facets

Index facets values and support facet numbers

Cargo.lock

@@ -550,6 +550,12 @@ dependencies = [
  "cfg-if 0.1.10",
 ]
 
+[[package]]
+name = "maplit"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3e2e65a1a2e43cfcb47a895c4c8b10d1f4a61097f9f254f183aee60cad9c651d"
+
 [[package]]
 name = "matches"
 version = "0.1.8"
@@ -608,10 +614,12 @@ dependencies = [
  "levenshtein_automata",
  "linked-hash-map",
  "log",
+ "maplit",
  "memmap",
  "near-proximity",
  "obkv",
  "once_cell",
+ "ordered-float",
  "rayon",
  "ringtail",
  "roaring",
@@ -708,6 +716,15 @@ version = "11.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a170cebd8021a008ea92e4db85a72f80b35df514ec664b296fdcbb654eac0b2c"
 
+[[package]]
+name = "ordered-float"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9fe9037165d7023b1228bc4ae9a2fa1a2b0095eca6c2998c624723dfd01314a5"
+dependencies = [
+ "num-traits",
+]
+
 [[package]]
 name = "page_size"
 version = "0.4.2"

Cargo.toml

@@ -23,6 +23,7 @@ memmap = "0.7.0"
 near-proximity = { git = "https://github.com/Kerollmops/plane-sweep-proximity", rev = "6608205" }
 obkv = "0.1.0"
 once_cell = "1.4.0"
+ordered-float = "2.0.0"
 rayon = "1.3.1"
 ringtail = "0.3.0"
 roaring = "0.6.1"
@@ -44,6 +45,7 @@ stderrlog = "0.5.0"
 
 [dev-dependencies]
 criterion = "0.3.3"
+maplit = "1.0.2"
 
 [build-dependencies]
 fst = "0.4.4"

http-ui/Cargo.lock

@@ -989,6 +989,7 @@ dependencies = [
  "near-proximity",
  "obkv",
  "once_cell",
+ "ordered-float",
  "rayon",
  "ringtail",
  "roaring",
@@ -1205,6 +1206,15 @@ version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "624a8340c38c1b80fd549087862da4ba43e08858af025b236e509b6649fc13d5"
 
+[[package]]
+name = "ordered-float"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9fe9037165d7023b1228bc4ae9a2fa1a2b0095eca6c2998c624723dfd01314a5"
+dependencies = [
+ "num-traits",
+]
+
 [[package]]
 name = "page_size"
 version = "0.4.2"

http-ui/src/main.rs

@@ -1,5 +1,5 @@
 use std::borrow::Cow;
-use std::collections::HashSet;
+use std::collections::{HashMap, HashSet};
 use std::fs::{File, create_dir_all};
 use std::net::SocketAddr;
 use std::path::PathBuf;
@@ -210,6 +210,8 @@ enum UpdateMetaProgress {
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(deny_unknown_fields)]
+#[serde(rename_all = "camelCase")]
 struct Settings {
     #[serde(
         default,
@@ -224,6 +226,9 @@ struct Settings {
         skip_serializing_if = "Option::is_none",
     )]
     searchable_attributes: Option<Option<Vec<String>>>,
+
+    #[serde(default)]
+    faceted_attributes: Option<HashMap<String, String>>,
 }
 
 // Any value that is present is considered Some value, including null.
@@ -367,6 +372,11 @@ async fn main() -> anyhow::Result<()> {
                         }
                     }
 
+                    // We transpose the settings JSON struct into a real setting update.
+                    if let Some(facet_types) = settings.faceted_attributes {
+                        builder.set_faceted_fields(facet_types);
+                    }
+
                     let result = builder.execute(|indexing_step| {
                         let (current, total) = match indexing_step {
                             TransformFromUserIntoGenericFormat { documents_seen } => (documents_seen, None),

src/facet/facet_type.rs

@@ -0,0 +1,50 @@
+use std::error::Error;
+use std::fmt;
+use std::str::FromStr;
+
+use serde::{Serialize, Deserialize};
+
+#[derive(Debug, Copy, Clone, PartialOrd, Ord, PartialEq, Eq, Hash)]
+#[derive(Serialize, Deserialize)]
+pub enum FacetType {
+    String,
+    Float,
+    Integer,
+}
+
+impl fmt::Display for FacetType {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            FacetType::String => f.write_str("string"),
+            FacetType::Float => f.write_str("float"),
+            FacetType::Integer => f.write_str("integer"),
+        }
+    }
+}
+
+impl FromStr for FacetType {
+    type Err = InvalidFacetType;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        if s.eq_ignore_ascii_case("string") {
+            Ok(FacetType::String)
+        } else if s.eq_ignore_ascii_case("float") {
+            Ok(FacetType::Float)
+        } else if s.eq_ignore_ascii_case("integer") {
+            Ok(FacetType::Integer)
+        } else {
+            Err(InvalidFacetType)
+        }
+    }
+}
+
+#[derive(Debug, Copy, Clone, PartialOrd, Ord, PartialEq, Eq, Hash)]
+pub struct InvalidFacetType;
+
+impl fmt::Display for InvalidFacetType {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str(r#"Invalid facet type, must be "string", "float" or "integer""#)
+    }
+}
+
+impl Error for InvalidFacetType { }

src/facet/mod.rs

@@ -0,0 +1,4 @@
+mod facet_type;
+pub mod value_encoding;
+
+pub use self::facet_type::FacetType;

src/facet/value_encoding.rs

@@ -0,0 +1,69 @@
+// https://stackoverflow.com/a/43305015/1941280
+#[inline]
+pub fn f64_into_bytes(float: f64) -> Option<[u8; 8]> {
+    if float.is_finite() {
+        if float == 0.0 || float == -0.0 {
+            return Some(xor_first_bit(0.0_f64.to_be_bytes()));
+        } else if float.is_sign_negative() {
+            return Some(xor_all_bits(float.to_be_bytes()));
+        } else if float.is_sign_positive() {
+            return Some(xor_first_bit(float.to_be_bytes()));
+        }
+    }
+    None
+}
+
+#[inline]
+pub fn i64_into_bytes(int: i64) -> [u8; 8] {
+    xor_first_bit(int.to_be_bytes())
+}
+
+#[inline]
+pub fn i64_from_bytes(bytes: [u8; 8]) -> i64 {
+    i64::from_be_bytes(xor_first_bit(bytes))
+}
+
+#[inline]
+fn xor_first_bit(mut x: [u8; 8]) -> [u8; 8] {
+    x[0] ^= 0x80;
+    x
+}
+
+#[inline]
+fn xor_all_bits(mut x: [u8; 8]) -> [u8; 8] {
+    x.iter_mut().for_each(|b| *b ^= 0xff);
+    x
+}
+
+#[cfg(test)]
+mod tests {
+    use std::cmp::Ordering::Less;
+    use super::*;
+
+    fn is_sorted<T: Ord>(x: &[T]) -> bool {
+        x.windows(2).map(|x| x[0].cmp(&x[1])).all(|o| o == Less)
+    }
+
+    #[test]
+    fn ordered_f64_bytes() {
+        let a = -13_f64;
+        let b = -10.0;
+        let c = -0.0;
+        let d =  1.0;
+        let e =  43.0;
+
+        let vec: Vec<_> = [a, b, c, d, e].iter().cloned().map(f64_into_bytes).collect();
+        assert!(is_sorted(&vec), "{:?}", vec);
+    }
+
+    #[test]
+    fn ordered_i64_bytes() {
+        let a = -10_i64;
+        let b = -0_i64;
+        let c =  1_i64;
+        let d =  43_i64;
+
+        let vec: Vec<_> = [a, b, c, d].iter().cloned().map(i64_into_bytes).collect();
+        assert!(is_sorted(&vec), "{:?}", vec);
+    }
+}

src/heed_codec/facet/facet_value_f64_codec.rs

@@ -0,0 +1,50 @@
+use std::borrow::Cow;
+use std::convert::TryInto;
+
+use crate::facet::value_encoding::f64_into_bytes;
+
+pub struct FacetValueF64Codec;
+
+impl<'a> heed::BytesDecode<'a> for FacetValueF64Codec {
+    type DItem = (u8, f64);
+
+    fn bytes_decode(bytes: &'a [u8]) -> Option<Self::DItem> {
+        let (field_id, buffer) = bytes.split_first()?;
+        let value = buffer[8..].try_into().ok().map(f64::from_be_bytes)?;
+        Some((*field_id, value))
+    }
+}
+
+impl heed::BytesEncode<'_> for FacetValueF64Codec {
+    type EItem = (u8, f64);
+
+    fn bytes_encode((field_id, value): &Self::EItem) -> Option<Cow<[u8]>> {
+        let mut buffer = [0u8; 16];
+
+        // Write the globally ordered float.
+        let bytes = f64_into_bytes(*value)?;
+        buffer[..8].copy_from_slice(&bytes[..]);
+
+        // Then the f64 value just to be able to read it back.
+        let bytes = value.to_be_bytes();
+        buffer[8..].copy_from_slice(&bytes[..]);
+
+        let mut bytes = Vec::with_capacity(buffer.len() + 1);
+        bytes.push(*field_id);
+        bytes.extend_from_slice(&buffer[..]);
+        Some(Cow::Owned(bytes))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use heed::{BytesEncode, BytesDecode};
+    use super::*;
+
+    #[test]
+    fn globally_ordered_f64() {
+        let bytes = FacetValueF64Codec::bytes_encode(&(3, -32.0)).unwrap();
+        let (name, value) = FacetValueF64Codec::bytes_decode(&bytes).unwrap();
+        assert_eq!((name, value), (3, -32.0));
+    }
+}

src/heed_codec/facet/facet_value_i64_codec.rs

@@ -0,0 +1,28 @@
+use std::borrow::Cow;
+use std::convert::TryInto;
+
+use crate::facet::value_encoding::{i64_from_bytes, i64_into_bytes};
+
+pub struct FacetValueI64Codec;
+
+impl<'a> heed::BytesDecode<'a> for FacetValueI64Codec {
+    type DItem = (u8, i64);
+
+    fn bytes_decode(bytes: &'a [u8]) -> Option<Self::DItem> {
+        let (field_id, buffer) = bytes.split_first()?;
+        let value = buffer.try_into().map(i64_from_bytes).ok()?;
+        Some((*field_id, value))
+    }
+}
+
+impl heed::BytesEncode<'_> for FacetValueI64Codec {
+    type EItem = (u8, i64);
+
+    fn bytes_encode((field_id, value): &Self::EItem) -> Option<Cow<[u8]>> {
+        let value = i64_into_bytes(*value);
+        let mut bytes = Vec::with_capacity(value.len() + 1);
+        bytes.push(*field_id);
+        bytes.extend_from_slice(&value[..]);
+        Some(Cow::Owned(bytes))
+    }
+}

src/heed_codec/facet/facet_value_string_codec.rs

@@ -0,0 +1,25 @@
+use std::borrow::Cow;
+use std::str;
+
+pub struct FacetValueStringCodec;
+
+impl<'a> heed::BytesDecode<'a> for FacetValueStringCodec {
+    type DItem = (u8, &'a str);
+
+    fn bytes_decode(bytes: &'a [u8]) -> Option<Self::DItem> {
+        let (field_id, bytes) = bytes.split_first()?;
+        let value = str::from_utf8(bytes).ok()?;
+        Some((*field_id, value))
+    }
+}
+
+impl<'a> heed::BytesEncode<'a> for FacetValueStringCodec {
+    type EItem = (u8, &'a str);
+
+    fn bytes_encode((field_id, value): &Self::EItem) -> Option<Cow<[u8]>> {
+        let mut bytes = Vec::with_capacity(value.len() + 1);
+        bytes.push(*field_id);
+        bytes.extend_from_slice(value.as_bytes());
+        Some(Cow::Owned(bytes))
+    }
+}

src/heed_codec/facet/mod.rs

@@ -0,0 +1,7 @@
+mod facet_value_f64_codec;
+mod facet_value_i64_codec;
+mod facet_value_string_codec;
+
+pub use self::facet_value_f64_codec::FacetValueF64Codec;
+pub use self::facet_value_i64_codec::FacetValueI64Codec;
+pub use self::facet_value_string_codec::FacetValueStringCodec;

src/heed_codec/mod.rs

@@ -4,6 +4,7 @@ mod cbo_roaring_bitmap_codec;
 mod obkv_codec;
 mod roaring_bitmap_codec;
 mod str_str_u8_codec;
+pub mod facet;
 
 pub use self::beu32_str_codec::BEU32StrCodec;
 pub use self::bo_roaring_bitmap_codec::BoRoaringBitmapCodec;

src/index.rs

@@ -1,4 +1,5 @@
 use std::borrow::Cow;
+use std::collections::HashMap;
 use std::path::Path;
 
 use anyhow::Context;
@@ -6,9 +7,10 @@ use heed::types::*;
 use heed::{PolyDatabase, Database, RwTxn, RoTxn};
 use roaring::RoaringBitmap;
 
+use crate::facet::FacetType;
+use crate::fields_ids_map::FieldsIdsMap;
 use crate::Search;
 use crate::{BEU32, DocumentId};
-use crate::fields_ids_map::FieldsIdsMap;
 use crate::{
     RoaringBitmapCodec, BEU32StrCodec, StrStrU8Codec, ObkvCodec,
     BoRoaringBitmapCodec, CboRoaringBitmapCodec,
@@ -16,6 +18,7 @@ use crate::{
 
 pub const DISPLAYED_FIELDS_KEY: &str = "displayed-fields";
 pub const DOCUMENTS_IDS_KEY: &str = "documents-ids";
+pub const FACETED_FIELDS_KEY: &str = "faceted-fields";
 pub const FIELDS_IDS_MAP_KEY: &str = "fields-ids-map";
 pub const PRIMARY_KEY_KEY: &str = "primary-key";
 pub const SEARCHABLE_FIELDS_KEY: &str = "searchable-fields";
@@ -34,22 +37,33 @@ pub struct Index {
     pub docid_word_positions: Database<BEU32StrCodec, BoRoaringBitmapCodec>,
     /// Maps the proximity between a pair of words with all the docids where this relation appears.
     pub word_pair_proximity_docids: Database<StrStrU8Codec, CboRoaringBitmapCodec>,
+    /// Maps the facet field id and the globally ordered value with the docids that corresponds to it.
+    pub facet_field_id_value_docids: Database<ByteSlice, CboRoaringBitmapCodec>,
     /// Maps the document id to the document as an obkv store.
     pub documents: Database<OwnedType<BEU32>, ObkvCodec>,
 }
 
 impl Index {
     pub fn new<P: AsRef<Path>>(mut options: heed::EnvOpenOptions, path: P) -> anyhow::Result<Index> {
-        options.max_dbs(5);
+        options.max_dbs(6);
 
         let env = options.open(path)?;
         let main = env.create_poly_database(Some("main"))?;
         let word_docids = env.create_database(Some("word-docids"))?;
         let docid_word_positions = env.create_database(Some("docid-word-positions"))?;
         let word_pair_proximity_docids = env.create_database(Some("word-pair-proximity-docids"))?;
+        let facet_field_id_value_docids = env.create_database(Some("facet-field-id-value-docids"))?;
         let documents = env.create_database(Some("documents"))?;
 
-        Ok(Index { env, main, word_docids, docid_word_positions, word_pair_proximity_docids, documents })
+        Ok(Index {
+            env,
+            main,
+            word_docids,
+            docid_word_positions,
+            word_pair_proximity_docids,
+            facet_field_id_value_docids,
+            documents,
+        })
     }
 
     /// Create a write transaction to be able to write into the index.
@@ -175,6 +189,24 @@ impl Index {
         self.main.get::<_, Str, ByteSlice>(rtxn, SEARCHABLE_FIELDS_KEY)
     }
 
+    /* faceted fields */
+
+    /// Writes the facet fields ids associated with their facet type or `None` if
+    /// the facet type is currently unknown.
+    pub fn put_faceted_fields(&self, wtxn: &mut RwTxn, fields_types: &HashMap<u8, FacetType>) -> heed::Result<()> {
+        self.main.put::<_, Str, SerdeJson<_>>(wtxn, FACETED_FIELDS_KEY, fields_types)
+    }
+
+    /// Deletes the facet fields ids associated with their facet type.
+    pub fn delete_faceted_fields(&self, wtxn: &mut RwTxn) -> heed::Result<bool> {
+        self.main.delete::<_, Str>(wtxn, FACETED_FIELDS_KEY)
+    }
+
+    /// Returns the facet fields ids associated with their facet type.
+    pub fn faceted_fields(&self, wtxn: &RoTxn) -> heed::Result<HashMap<u8, FacetType>> {
+        Ok(self.main.get::<_, Str, SerdeJson<_>>(wtxn, FACETED_FIELDS_KEY)?.unwrap_or_default())
+    }
+
     /* words fst */
 
     /// Writes the FST which is the words dictionnary of the engine.

src/lib.rs

@@ -4,6 +4,7 @@ mod index;
 mod mdfs;
 mod query_tokens;
 mod search;
+pub mod facet;
 pub mod heed_codec;
 pub mod proximity;
 pub mod subcommand;
@@ -33,6 +34,7 @@ pub type FastMap8<K, V> = HashMap<K, V, BuildHasherDefault<FxHasher64>>;
 pub type SmallString32 = smallstr::SmallString<[u8; 32]>;
 pub type SmallVec32<T> = smallvec::SmallVec<[T; 32]>;
 pub type SmallVec16<T> = smallvec::SmallVec<[T; 16]>;
+pub type SmallVec8<T> = smallvec::SmallVec<[T; 8]>;
 pub type BEU32 = heed::zerocopy::U32<heed::byteorder::BE>;
 pub type BEU64 = heed::zerocopy::U64<heed::byteorder::BE>;
 pub type DocumentId = u32;
@@ -60,9 +62,9 @@ pub fn obkv_to_json(
 }
 
 /// Transform a JSON value into a string that can be indexed.
-pub fn json_to_string(value: Value) -> Option<String> {
+pub fn json_to_string(value: &Value) -> Option<String> {
 
-    fn inner(value: Value, output: &mut String) -> bool {
+    fn inner(value: &Value, output: &mut String) -> bool {
         use std::fmt::Write;
         match value {
             Value::Null => false,
@@ -121,7 +123,7 @@ mod tests {
             "not_there": null,
         });
 
-        let string = json_to_string(value).unwrap();
+        let string = json_to_string(&value).unwrap();
         assert_eq!(string, "name: John Doe. age: 43. ");
     }
 
@@ -135,7 +137,7 @@ mod tests {
             null,
         ]);
 
-        let string = json_to_string(value).unwrap();
+        let string = json_to_string(&value).unwrap();
         // We don't care about having two point (.) after the other as
         // the distance of hard separators is clamped to 8 anyway.
         assert_eq!(string, "name: John Doe. . 43. hello. I. am. fine. . ");

src/subcommand/infos.rs

@@ -78,6 +78,16 @@ enum Command {
         words: Vec<String>,
     },
 
+    /// Outputs a CSV with the documents ids along with the facet values where it appears.
+    FacetValuesDocids {
+        /// Display the whole documents ids in details.
+        #[structopt(long)]
+        full_display: bool,
+
+        /// The field name in the document.
+        field_name: String,
+    },
+
     /// Outputs the total size of all the docid-word-positions keys and values.
     TotalDocidWordPositionsSize,
 
@@ -147,6 +157,9 @@ pub fn run(opt: Opt) -> anyhow::Result<()> {
         MostCommonWords { limit } => most_common_words(&index, &rtxn, limit),
         BiggestValues { limit } => biggest_value_sizes(&index, &rtxn, limit),
         WordsDocids { full_display, words } => words_docids(&index, &rtxn, !full_display, words),
+        FacetValuesDocids { full_display, field_name } => {
+            facet_values_docids(&index, &rtxn, !full_display, field_name)
+        },
         TotalDocidWordPositionsSize => total_docid_word_positions_size(&index, &rtxn),
         AverageNumberOfWordsByDoc => average_number_of_words_by_doc(&index, &rtxn),
         AverageNumberOfPositionsByWord => {
@@ -256,6 +269,64 @@ fn words_docids(index: &Index, rtxn: &heed::RoTxn, debug: bool, words: Vec<Strin
     Ok(wtr.flush()?)
 }
 
+fn facet_values_docids(index: &Index, rtxn: &heed::RoTxn, debug: bool, field_name: String) -> anyhow::Result<()> {
+    use crate::facet::FacetType;
+    use crate::heed_codec::facet::{FacetValueStringCodec, FacetValueF64Codec, FacetValueI64Codec};
+    use heed::{BytesDecode, Error::Decoding};
+
+    let fields_ids_map = index.fields_ids_map(&rtxn)?;
+    let faceted_fields = index.faceted_fields(&rtxn)?;
+
+    let field_id = fields_ids_map.id(&field_name)
+        .with_context(|| format!("field {} not found", field_name))?;
+    let field_type = faceted_fields.get(&field_id)
+        .with_context(|| format!("field {} is not faceted", field_name))?;
+
+    let iter = index.facet_field_id_value_docids.prefix_iter(&rtxn, &[field_id])?;
+    let iter = match field_type {
+        FacetType::String => {
+            let iter = iter
+                .map(|result| result.and_then(|(key, value)| {
+                    let (_, key) = FacetValueStringCodec::bytes_decode(key).ok_or(Decoding)?;
+                    Ok((key.to_string(), value))
+                }));
+            Box::new(iter) as Box<dyn Iterator<Item=_>>
+        },
+        FacetType::Float => {
+            let iter = iter
+                .map(|result| result.and_then(|(key, value)| {
+                    let (_, key) = FacetValueF64Codec::bytes_decode(key).ok_or(Decoding)?;
+                    Ok((key.to_string(), value))
+                }));
+            Box::new(iter)
+        },
+        FacetType::Integer => {
+            let iter = iter
+                .map(|result| result.and_then(|(key, value)| {
+                    let (_, key) = FacetValueI64Codec::bytes_decode(key).ok_or(Decoding)?;
+                    Ok((key.to_string(), value))
+                }));
+            Box::new(iter)
+        },
+    };
+
+    let stdout = io::stdout();
+    let mut wtr = csv::Writer::from_writer(stdout.lock());
+    wtr.write_record(&["facet_value", "documents_ids"])?;
+
+    for result in iter {
+        let (value, docids) = result?;
+        let docids = if debug {
+            format!("{:?}", docids)
+        } else {
+            format!("{:?}", docids.iter().collect::<Vec<_>>())
+        };
+        wtr.write_record(&[value, docids])?;
+    }
+
+    Ok(wtr.flush()?)
+}
+
 fn export_words_fst(index: &Index, rtxn: &heed::RoTxn, output: PathBuf) -> anyhow::Result<()> {
     use std::fs::File;
     use std::io::Write as _;

src/update/clear_documents.rs

@@ -18,33 +18,25 @@ impl<'t, 'u, 'i> ClearDocuments<'t, 'u, 'i> {
             word_docids,
             docid_word_positions,
             word_pair_proximity_docids,
+            facet_field_id_value_docids,
             documents,
         } = self.index;
 
-        // We clear the word fst.
+        // We retrieve the number of documents ids that we are deleting.
+        let number_of_documents = self.index.number_of_documents(self.wtxn)?;
+
+        // We clean some of the main engine datastructures.
         self.index.put_words_fst(self.wtxn, &fst::Set::default())?;
-
-        // We clear the users ids documents ids.
         self.index.put_users_ids_documents_ids(self.wtxn, &fst::Map::default())?;
-
-        // We retrieve the documents ids.
-        let documents_ids = self.index.documents_ids(self.wtxn)?;
-
-        // We clear the internal documents ids.
         self.index.put_documents_ids(self.wtxn, &RoaringBitmap::default())?;
 
-        // We clear the word docids.
+        // Clear the other databases.
         word_docids.clear(self.wtxn)?;
-
-        // We clear the docid word positions.
         docid_word_positions.clear(self.wtxn)?;
-
-        // We clear the word pair proximity docids.
         word_pair_proximity_docids.clear(self.wtxn)?;
-
-        // We clear the documents themselves.
+        facet_field_id_value_docids.clear(self.wtxn)?;
         documents.clear(self.wtxn)?;
 
-        Ok(documents_ids.len() as usize)
+        Ok(number_of_documents)
     }
 }

src/update/delete_documents.rs

@@ -76,6 +76,7 @@ impl<'t, 'u, 'i> DeleteDocuments<'t, 'u, 'i> {
             word_docids,
             docid_word_positions,
             word_pair_proximity_docids,
+            facet_field_id_value_docids,
             documents,
         } = self.index;
 
@@ -158,7 +159,9 @@ impl<'t, 'u, 'i> DeleteDocuments<'t, 'u, 'i> {
         }
 
         // We construct an FST set that contains the words to delete from the words FST.
-        let words_to_delete = words.iter().filter_map(|(w, d)| if *d { Some(w.as_ref()) } else { None });
+        let words_to_delete = words.iter().filter_map(|(word, must_remove)| {
+            if *must_remove { Some(word.as_ref()) } else { None }
+        });
         let words_to_delete = fst::Set::from_iter(words_to_delete)?;
 
         let new_words_fst = {
@@ -191,6 +194,20 @@ impl<'t, 'u, 'i> DeleteDocuments<'t, 'u, 'i> {
             }
         }
 
+        drop(iter);
+
+        // We delete the documents ids that are under the facet field id values.
+        let mut iter = facet_field_id_value_docids.iter_mut(self.wtxn)?;
+        while let Some(result) = iter.next() {
+            let (bytes, mut docids) = result?;
+            docids.difference_with(&self.documents_ids);
+            if docids.is_empty() {
+                iter.del_current()?;
+            } else {
+                iter.put_current(bytes, &docids)?;
+            }
+        }
+
         Ok(self.documents_ids.len() as usize)
     }
 }

src/update/index_documents/merge_function.rs

@@ -29,23 +29,13 @@ pub fn main_merge(key: &[u8], values: &[Cow<[u8]>]) -> anyhow::Result<Vec<u8>> {
             ensure!(values.windows(2).all(|vs| vs[0] == vs[1]), "fields ids map doesn't match");
             Ok(values[0].to_vec())
         },
-        DOCUMENTS_IDS_KEY => word_docids_merge(&[], values),
+        DOCUMENTS_IDS_KEY => roaring_bitmap_merge(values),
         otherwise => bail!("wut {:?}", otherwise),
     }
 }
 
 pub fn word_docids_merge(_key: &[u8], values: &[Cow<[u8]>]) -> anyhow::Result<Vec<u8>> {
-    let (head, tail) = values.split_first().unwrap();
-    let mut head = RoaringBitmap::deserialize_from(&head[..])?;
-
-    for value in tail {
-        let bitmap = RoaringBitmap::deserialize_from(&value[..])?;
-        head.union_with(&bitmap);
-    }
-
-    let mut vec = Vec::with_capacity(head.serialized_size());
-    head.serialize_into(&mut vec)?;
-    Ok(vec)
+    roaring_bitmap_merge(values)
 }
 
 pub fn docid_word_positions_merge(key: &[u8], _values: &[Cow<[u8]>]) -> anyhow::Result<Vec<u8>> {
@@ -53,17 +43,11 @@ pub fn docid_word_positions_merge(key: &[u8], _values: &[Cow<[u8]>]) -> anyhow::
 }
 
 pub fn words_pairs_proximities_docids_merge(_key: &[u8], values: &[Cow<[u8]>]) -> anyhow::Result<Vec<u8>> {
-    let (head, tail) = values.split_first().unwrap();
-    let mut head = CboRoaringBitmapCodec::deserialize_from(&head[..])?;
+    cbo_roaring_bitmap_merge(values)
+}
 
-    for value in tail {
-        let bitmap = CboRoaringBitmapCodec::deserialize_from(&value[..])?;
-        head.union_with(&bitmap);
-    }
-
-    let mut vec = Vec::new();
-    CboRoaringBitmapCodec::serialize_into(&head, &mut vec)?;
-    Ok(vec)
+pub fn facet_field_value_docids_merge(_key: &[u8], values: &[Cow<[u8]>]) -> anyhow::Result<Vec<u8>> {
+    cbo_roaring_bitmap_merge(values)
 }
 
 pub fn documents_merge(key: &[u8], _values: &[Cow<[u8]>]) -> anyhow::Result<Vec<u8>> {
@@ -85,3 +69,31 @@ pub fn merge_two_obkvs(base: obkv::KvReader, update: obkv::KvReader, buffer: &mu
 
     writer.finish().unwrap();
 }
+
+fn roaring_bitmap_merge(values: &[Cow<[u8]>]) -> anyhow::Result<Vec<u8>> {
+    let (head, tail) = values.split_first().unwrap();
+    let mut head = RoaringBitmap::deserialize_from(&head[..])?;
+
+    for value in tail {
+        let bitmap = RoaringBitmap::deserialize_from(&value[..])?;
+        head.union_with(&bitmap);
+    }
+
+    let mut vec = Vec::with_capacity(head.serialized_size());
+    head.serialize_into(&mut vec)?;
+    Ok(vec)
+}
+
+fn cbo_roaring_bitmap_merge(values: &[Cow<[u8]>]) -> anyhow::Result<Vec<u8>> {
+    let (head, tail) = values.split_first().unwrap();
+    let mut head = CboRoaringBitmapCodec::deserialize_from(&head[..])?;
+
+    for value in tail {
+        let bitmap = CboRoaringBitmapCodec::deserialize_from(&value[..])?;
+        head.union_with(&bitmap);
+    }
+
+    let mut vec = Vec::new();
+    CboRoaringBitmapCodec::serialize_into(&head, &mut vec)?;
+    Ok(vec)
+}

src/update/index_documents/mod.rs

@@ -16,10 +16,10 @@ use rayon::ThreadPool;
 
 use crate::index::Index;
 use crate::update::UpdateIndexingStep;
-use self::store::Store;
+use self::store::{Store, Readers};
 use self::merge_function::{
     main_merge, word_docids_merge, words_pairs_proximities_docids_merge,
-    docid_word_positions_merge, documents_merge,
+    docid_word_positions_merge, documents_merge, facet_field_value_docids_merge,
 };
 pub use self::transform::{Transform, TransformOutput};
 
@@ -327,8 +327,10 @@ impl<'t, 'u, 'i, 'a> IndexDocuments<'t, 'u, 'i, 'a> {
         enum DatabaseType {
             Main,
             WordDocids,
+            FacetValuesDocids,
         }
 
+        let faceted_fields = self.index.faceted_fields(self.wtxn)?;
         let searchable_fields: HashSet<_> = match self.index.searchable_fields(self.wtxn)? {
             Some(fields) => fields.iter().copied().collect(),
             None => fields_ids_map.iter().map(|(id, _name)| id).collect(),
@@ -362,6 +364,7 @@ impl<'t, 'u, 'i, 'a> IndexDocuments<'t, 'u, 'i, 'a> {
                 .map(|(i, documents)| {
                     let store = Store::new(
                         searchable_fields.clone(),
+                        faceted_fields.clone(),
                         linked_hash_map_size,
                         max_nb_chunks,
                         max_memory_by_job,
@@ -384,13 +387,23 @@ impl<'t, 'u, 'i, 'a> IndexDocuments<'t, 'u, 'i, 'a> {
             let mut word_docids_readers = Vec::with_capacity(readers.len());
             let mut docid_word_positions_readers = Vec::with_capacity(readers.len());
             let mut words_pairs_proximities_docids_readers = Vec::with_capacity(readers.len());
+            let mut facet_field_value_docids_readers = Vec::with_capacity(readers.len());
             let mut documents_readers = Vec::with_capacity(readers.len());
             readers.into_iter().for_each(|readers| {
-                main_readers.push(readers.main);
-                word_docids_readers.push(readers.word_docids);
-                docid_word_positions_readers.push(readers.docid_word_positions);
-                words_pairs_proximities_docids_readers.push(readers.words_pairs_proximities_docids);
-                documents_readers.push(readers.documents);
+                let Readers {
+                    main,
+                    word_docids,
+                    docid_word_positions,
+                    words_pairs_proximities_docids,
+                    facet_field_value_docids,
+                    documents
+                } = readers;
+                main_readers.push(main);
+                word_docids_readers.push(word_docids);
+                docid_word_positions_readers.push(docid_word_positions);
+                words_pairs_proximities_docids_readers.push(words_pairs_proximities_docids);
+                facet_field_value_docids_readers.push(facet_field_value_docids);
+                documents_readers.push(documents);
             });
 
             // This is the function that merge the readers
@@ -413,6 +426,11 @@ impl<'t, 'u, 'i, 'a> IndexDocuments<'t, 'u, 'i, 'a> {
                 vec![
                     (DatabaseType::Main, main_readers, main_merge as MergeFn),
                     (DatabaseType::WordDocids, word_docids_readers, word_docids_merge),
+                    (
+                        DatabaseType::FacetValuesDocids,
+                        facet_field_value_docids_readers,
+                        facet_field_value_docids_merge,
+                    ),
                 ]
                 .into_par_iter()
                 .for_each(|(dbtype, readers, merge)| {
@@ -463,9 +481,11 @@ impl<'t, 'u, 'i, 'a> IndexDocuments<'t, 'u, 'i, 'a> {
         self.index.put_documents_ids(self.wtxn, &documents_ids)?;
 
         let mut database_count = 0;
+        let total_databases = 6;
+
         progress_callback(UpdateIndexingStep::MergeDataIntoFinalDatabase {
             databases_seen: 0,
-            total_databases: 5,
+            total_databases,
         });
 
         debug!("Writing the docid word positions into LMDB on disk...");
@@ -480,7 +500,7 @@ impl<'t, 'u, 'i, 'a> IndexDocuments<'t, 'u, 'i, 'a> {
         database_count += 1;
         progress_callback(UpdateIndexingStep::MergeDataIntoFinalDatabase {
             databases_seen: database_count,
-            total_databases: 5,
+            total_databases,
         });
 
         debug!("Writing the documents into LMDB on disk...");
@@ -495,7 +515,7 @@ impl<'t, 'u, 'i, 'a> IndexDocuments<'t, 'u, 'i, 'a> {
         database_count += 1;
         progress_callback(UpdateIndexingStep::MergeDataIntoFinalDatabase {
             databases_seen: database_count,
-            total_databases: 5,
+            total_databases,
         });
 
         debug!("Writing the words pairs proximities docids into LMDB on disk...");
@@ -510,7 +530,7 @@ impl<'t, 'u, 'i, 'a> IndexDocuments<'t, 'u, 'i, 'a> {
         database_count += 1;
         progress_callback(UpdateIndexingStep::MergeDataIntoFinalDatabase {
             databases_seen: database_count,
-            total_databases: 5,
+            total_databases,
         });
 
         for (db_type, result) in receiver {
@@ -537,16 +557,27 @@ impl<'t, 'u, 'i, 'a> IndexDocuments<'t, 'u, 'i, 'a> {
                         write_method,
                     )?;
                 },
+                DatabaseType::FacetValuesDocids => {
+                    debug!("Writing the facet values docids into LMDB on disk...");
+                    let db = *self.index.facet_field_id_value_docids.as_polymorph();
+                    write_into_lmdb_database(
+                        self.wtxn,
+                        db,
+                        content,
+                        facet_field_value_docids_merge,
+                        write_method,
+                    )?;
+                },
             }
 
             database_count += 1;
             progress_callback(UpdateIndexingStep::MergeDataIntoFinalDatabase {
                 databases_seen: database_count,
-                total_databases: 5,
+                total_databases,
             });
         }
 
-        debug_assert_eq!(database_count, 5);
+        debug_assert_eq!(database_count, total_databases);
 
         info!("Transform output indexed in {:.02?}", before_indexing.elapsed());
 

src/update/index_documents/store.rs

@@ -1,3 +1,4 @@
+use std::borrow::Cow;
 use std::collections::{BTreeMap, HashMap, HashSet};
 use std::convert::{TryFrom, TryInto};
 use std::fs::File;
@@ -5,22 +6,29 @@ use std::iter::FromIterator;
 use std::time::Instant;
 use std::{cmp, iter};
 
-use anyhow::Context;
+use anyhow::{bail, Context};
 use bstr::ByteSlice as _;
+use grenad::{Reader, FileFuse, Writer, Sorter, CompressionType};
 use heed::BytesEncode;
 use linked_hash_map::LinkedHashMap;
 use log::{debug, info};
-use grenad::{Reader, FileFuse, Writer, Sorter, CompressionType};
+use ordered_float::OrderedFloat;
 use roaring::RoaringBitmap;
+use serde_json::Value;
 use tempfile::tempfile;
 
+use crate::facet::FacetType;
 use crate::heed_codec::{BoRoaringBitmapCodec, CboRoaringBitmapCodec};
+use crate::heed_codec::facet::{FacetValueStringCodec, FacetValueF64Codec, FacetValueI64Codec};
 use crate::tokenizer::{simple_tokenizer, only_token};
 use crate::update::UpdateIndexingStep;
-use crate::{json_to_string, SmallVec32, Position, DocumentId};
+use crate::{json_to_string, SmallVec8, SmallVec32, SmallString32, Position, DocumentId};
 
 use super::{MergeFn, create_writer, create_sorter, writer_into_reader};
-use super::merge_function::{main_merge, word_docids_merge, words_pairs_proximities_docids_merge};
+use super::merge_function::{
+    main_merge, word_docids_merge, words_pairs_proximities_docids_merge,
+    facet_field_value_docids_merge,
+};
 
 const LMDB_MAX_KEY_LENGTH: usize = 511;
 const ONE_KILOBYTE: usize = 1024 * 1024;
@@ -33,17 +41,21 @@ pub struct Readers {
     pub word_docids: Reader<FileFuse>,
     pub docid_word_positions: Reader<FileFuse>,
     pub words_pairs_proximities_docids: Reader<FileFuse>,
+    pub facet_field_value_docids: Reader<FileFuse>,
     pub documents: Reader<FileFuse>,
 }
 
 pub struct Store {
     // Indexing parameters
     searchable_fields: HashSet<u8>,
+    faceted_fields: HashMap<u8, FacetType>,
     // Caches
     word_docids: LinkedHashMap<SmallVec32<u8>, RoaringBitmap>,
     word_docids_limit: usize,
     words_pairs_proximities_docids: LinkedHashMap<(SmallVec32<u8>, SmallVec32<u8>, u8), RoaringBitmap>,
     words_pairs_proximities_docids_limit: usize,
+    facet_field_value_docids: LinkedHashMap<(u8, FacetValue), RoaringBitmap>,
+    facet_field_value_docids_limit: usize,
     // MTBL parameters
     chunk_compression_type: CompressionType,
     chunk_compression_level: Option<u32>,
@@ -52,6 +64,7 @@ pub struct Store {
     main_sorter: Sorter<MergeFn>,
     word_docids_sorter: Sorter<MergeFn>,
     words_pairs_proximities_docids_sorter: Sorter<MergeFn>,
+    facet_field_value_docids_sorter: Sorter<MergeFn>,
     // MTBL writers
     docid_word_positions_writer: Writer<File>,
     documents_writer: Writer<File>,
@@ -60,6 +73,7 @@ pub struct Store {
 impl Store {
     pub fn new(
         searchable_fields: HashSet<u8>,
+        faceted_fields: HashMap<u8, FacetType>,
         linked_hash_map_size: Option<usize>,
         max_nb_chunks: Option<usize>,
         max_memory: Option<usize>,
@@ -69,7 +83,7 @@ impl Store {
     ) -> anyhow::Result<Store>
     {
         // We divide the max memory by the number of sorter the Store have.
-        let max_memory = max_memory.map(|mm| cmp::max(ONE_KILOBYTE, mm / 3));
+        let max_memory = max_memory.map(|mm| cmp::max(ONE_KILOBYTE, mm / 4));
         let linked_hash_map_size = linked_hash_map_size.unwrap_or(500);
 
         let main_sorter = create_sorter(
@@ -96,6 +110,14 @@ impl Store {
             max_nb_chunks,
             max_memory,
         );
+        let facet_field_value_docids_sorter = create_sorter(
+            facet_field_value_docids_merge,
+            chunk_compression_type,
+            chunk_compression_level,
+            chunk_fusing_shrink_size,
+            max_nb_chunks,
+            max_memory,
+        );
 
         let documents_writer = tempfile().and_then(|f| {
             create_writer(chunk_compression_type, chunk_compression_level, f)
@@ -107,11 +129,14 @@ impl Store {
         Ok(Store {
             // Indexing parameters.
             searchable_fields,
+            faceted_fields,
             // Caches
             word_docids: LinkedHashMap::with_capacity(linked_hash_map_size),
             word_docids_limit: linked_hash_map_size,
             words_pairs_proximities_docids: LinkedHashMap::with_capacity(linked_hash_map_size),
             words_pairs_proximities_docids_limit: linked_hash_map_size,
+            facet_field_value_docids: LinkedHashMap::with_capacity(linked_hash_map_size),
+            facet_field_value_docids_limit: linked_hash_map_size,
             // MTBL parameters
             chunk_compression_type,
             chunk_compression_level,
@@ -120,6 +145,7 @@ impl Store {
             main_sorter,
             word_docids_sorter,
             words_pairs_proximities_docids_sorter,
+            facet_field_value_docids_sorter,
             // MTBL writers
             docid_word_positions_writer,
             documents_writer,
@@ -147,6 +173,35 @@ impl Store {
         Ok(())
     }
 
+    // Save the documents ids under the facet field id and value we have seen it.
+    fn insert_facet_values_docid(
+        &mut self,
+        field_id: u8,
+        field_value: FacetValue,
+        id: DocumentId,
+    ) -> anyhow::Result<()>
+    {
+        let key = (field_id, field_value);
+        // if get_refresh finds the element it is assured to be at the end of the linked hash map.
+        match self.facet_field_value_docids.get_refresh(&key) {
+            Some(old) => { old.insert(id); },
+            None => {
+                // A newly inserted element is append at the end of the linked hash map.
+                self.facet_field_value_docids.insert(key, RoaringBitmap::from_iter(Some(id)));
+                // If the word docids just reached it's capacity we must make sure to remove
+                // one element, this way next time we insert we doesn't grow the capacity.
+                if self.facet_field_value_docids.len() == self.facet_field_value_docids_limit {
+                    // Removing the front element is equivalent to removing the LRU element.
+                    Self::write_docid_facet_field_values(
+                        &mut self.facet_field_value_docids_sorter,
+                        self.facet_field_value_docids.pop_front(),
+                    )?;
+                }
+            }
+        }
+        Ok(())
+    }
+
     // Save the documents ids under the words pairs proximities that it contains.
     fn insert_words_pairs_proximities_docids<'a>(
         &mut self,
@@ -187,7 +242,8 @@ impl Store {
     fn write_document(
         &mut self,
         document_id: DocumentId,
-        words_positions: &HashMap<String, SmallVec32<Position>>,
+        words_positions: &mut HashMap<String, SmallVec32<Position>>,
+        facet_values: &mut HashMap<u8, SmallVec8<FacetValue>>,
         record: &[u8],
     ) -> anyhow::Result<()>
     {
@@ -196,13 +252,20 @@ impl Store {
         self.insert_words_pairs_proximities_docids(words_pair_proximities, document_id)?;
 
         // We store document_id associated with all the words the record contains.
-        for (word, _) in words_positions {
-            self.insert_word_docid(word, document_id)?;
+        for (word, _) in words_positions.drain() {
+            self.insert_word_docid(&word, document_id)?;
         }
 
         self.documents_writer.insert(document_id.to_be_bytes(), record)?;
         Self::write_docid_word_positions(&mut self.docid_word_positions_writer, document_id, words_positions)?;
 
+        // We store document_id associated with all the field id and values.
+        for (field, values) in facet_values.drain() {
+            for value in values {
+                self.insert_facet_values_docid(field, value, document_id)?;
+            }
+        }
+
         Ok(())
     }
 
@@ -263,6 +326,31 @@ impl Store {
         Ok(())
     }
 
+    fn write_docid_facet_field_values<I>(
+        sorter: &mut Sorter<MergeFn>,
+        iter: I,
+    ) -> anyhow::Result<()>
+    where I: IntoIterator<Item=((u8, FacetValue), RoaringBitmap)>
+    {
+        use FacetValue::*;
+
+        for ((field_id, value), docids) in iter {
+            let result = match value {
+                String(s) => FacetValueStringCodec::bytes_encode(&(field_id, &s)).map(Cow::into_owned),
+                Float(f) => FacetValueF64Codec::bytes_encode(&(field_id, *f)).map(Cow::into_owned),
+                Integer(i) => FacetValueI64Codec::bytes_encode(&(field_id, i)).map(Cow::into_owned),
+            };
+            let key = result.context("could not serialize facet key")?;
+            let bytes = CboRoaringBitmapCodec::bytes_encode(&docids)
+                .context("could not serialize docids")?;
+            if lmdb_key_valid_size(&key) {
+                sorter.insert(&key, &bytes)?;
+            }
+        }
+
+        Ok(())
+    }
+
     fn write_word_docids<I>(sorter: &mut Sorter<MergeFn>, iter: I) -> anyhow::Result<()>
     where I: IntoIterator<Item=(SmallVec32<u8>, RoaringBitmap)>
     {
@@ -301,6 +389,7 @@ impl Store {
 
         let mut before = Instant::now();
         let mut words_positions = HashMap::new();
+        let mut facet_values = HashMap::new();
 
         let mut count: usize = 0;
         while let Some((key, value)) = documents.next()? {
@@ -320,27 +409,34 @@ impl Store {
                 }
 
                 for (attr, content) in document.iter() {
-                    if !self.searchable_fields.contains(&attr) {
-                        continue;
-                    }
+                    if self.faceted_fields.contains_key(&attr) || self.searchable_fields.contains(&attr) {
+                        let value = serde_json::from_slice(content)?;
 
-                    let value = serde_json::from_slice(content)?;
-                    let content = match json_to_string(value) {
-                        Some(content) => content,
-                        None => continue,
-                    };
+                        if let Some(ftype) = self.faceted_fields.get(&attr) {
+                            let mut values = parse_facet_value(*ftype, &value).with_context(|| {
+                                format!("extracting facets from the value {}", value)
+                            })?;
+                            facet_values.entry(attr).or_insert_with(SmallVec8::new).extend(values.drain(..));
+                        }
 
-                    let tokens = simple_tokenizer(&content).filter_map(only_token);
-                    for (pos, token) in tokens.enumerate().take(MAX_POSITION) {
-                        let word = token.to_lowercase();
-                        let position = (attr as usize * MAX_POSITION + pos) as u32;
-                        words_positions.entry(word).or_insert_with(SmallVec32::new).push(position);
+                        if self.searchable_fields.contains(&attr) {
+                            let content = match json_to_string(&value) {
+                                Some(content) => content,
+                                None => continue,
+                            };
+
+                            let tokens = simple_tokenizer(&content).filter_map(only_token);
+                            for (pos, token) in tokens.enumerate().take(MAX_POSITION) {
+                                let word = token.to_lowercase();
+                                let position = (attr as usize * MAX_POSITION + pos) as u32;
+                                words_positions.entry(word).or_insert_with(SmallVec32::new).push(position);
+                            }
+                        }
                     }
                 }
 
                 // We write the document in the documents store.
-                self.write_document(document_id, &words_positions, value)?;
-                words_positions.clear();
+                self.write_document(document_id, &mut words_positions, &mut facet_values, value)?;
             }
 
             // Compute the document id of the next document.
@@ -367,6 +463,10 @@ impl Store {
             &mut self.words_pairs_proximities_docids_sorter,
             self.words_pairs_proximities_docids,
         )?;
+        Self::write_docid_facet_field_values(
+            &mut self.facet_field_value_docids_sorter,
+            self.facet_field_value_docids,
+        )?;
 
         let mut word_docids_wtr = tempfile().and_then(|f| create_writer(comp_type, comp_level, f))?;
         let mut builder = fst::SetBuilder::memory();
@@ -388,9 +488,13 @@ impl Store {
         let mut words_pairs_proximities_docids_wtr = tempfile().and_then(|f| create_writer(comp_type, comp_level, f))?;
         self.words_pairs_proximities_docids_sorter.write_into(&mut words_pairs_proximities_docids_wtr)?;
 
+        let mut facet_field_value_docids_wtr = tempfile().and_then(|f| create_writer(comp_type, comp_level, f))?;
+        self.facet_field_value_docids_sorter.write_into(&mut facet_field_value_docids_wtr)?;
+
         let main = writer_into_reader(main_wtr, shrink_size)?;
         let word_docids = writer_into_reader(word_docids_wtr, shrink_size)?;
         let words_pairs_proximities_docids = writer_into_reader(words_pairs_proximities_docids_wtr, shrink_size)?;
+        let facet_field_value_docids = writer_into_reader(facet_field_value_docids_wtr, shrink_size)?;
         let docid_word_positions = writer_into_reader(self.docid_word_positions_writer, shrink_size)?;
         let documents = writer_into_reader(self.documents_writer, shrink_size)?;
 
@@ -399,6 +503,7 @@ impl Store {
             word_docids,
             docid_word_positions,
             words_pairs_proximities_docids,
+            facet_field_value_docids,
             documents,
         })
     }
@@ -444,3 +549,70 @@ fn format_count(n: usize) -> String {
 fn lmdb_key_valid_size(key: &[u8]) -> bool {
     !key.is_empty() && key.len() <= LMDB_MAX_KEY_LENGTH
 }
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+enum FacetValue {
+    String(SmallString32),
+    Float(OrderedFloat<f64>),
+    Integer(i64),
+}
+
+fn parse_facet_value(ftype: FacetType, value: &Value) -> anyhow::Result<SmallVec8<FacetValue>> {
+    use FacetValue::*;
+
+    fn inner_parse_facet_value(
+        ftype: FacetType,
+        value: &Value,
+        can_recurse: bool,
+        output: &mut SmallVec8<FacetValue>,
+    ) -> anyhow::Result<()>
+    {
+        match value {
+            Value::Null => Ok(()),
+            Value::Bool(b) => Ok(output.push(Integer(*b as i64))),
+            Value::Number(number) => match ftype {
+                FacetType::String => bail!("invalid facet type, expecting {} found number", ftype),
+                FacetType::Float => match number.as_f64() {
+                    Some(float) => Ok(output.push(Float(OrderedFloat(float)))),
+                    None => bail!("invalid facet type, expecting {} found integer", ftype),
+                },
+                FacetType::Integer => match number.as_i64() {
+                    Some(integer) => Ok(output.push(Integer(integer))),
+                    None => if number.is_f64() {
+                        bail!("invalid facet type, expecting {} found float", ftype)
+                    } else {
+                        bail!("invalid facet type, expecting {} found out-of-bound integer (64bit)", ftype)
+                    },
+                },
+            },
+            Value::String(string) => {
+                let string = string.trim();
+                if string.is_empty() { return Ok(()) }
+                match ftype {
+                    FacetType::String => {
+                        let string = SmallString32::from(string);
+                        Ok(output.push(String(string)))
+                    },
+                    FacetType::Float => match string.parse() {
+                        Ok(float) => Ok(output.push(Float(OrderedFloat(float)))),
+                        Err(_err) => bail!("invalid facet type, expecting {} found string", ftype),
+                    },
+                    FacetType::Integer => match string.parse() {
+                        Ok(integer) => Ok(output.push(Integer(integer))),
+                        Err(_err) => bail!("invalid facet type, expecting {} found string", ftype),
+                    },
+                }
+            },
+            Value::Array(values) => if can_recurse {
+                values.iter().map(|v| inner_parse_facet_value(ftype, v, false, output)).collect()
+            } else {
+                bail!("invalid facet type, expecting {} found sub-array ()", ftype)
+            },
+            Value::Object(_) => bail!("invalid facet type, expecting {} found object", ftype),
+        }
+    }
+
+    let mut facet_values = SmallVec8::new();
+    inner_parse_facet_value(ftype, value, true, &mut facet_values)?;
+    Ok(facet_values)
+}

src/update/settings.rs

@@ -1,9 +1,13 @@
-use anyhow::Context;
+use std::collections::HashMap;
+use std::str::FromStr;
+
+use anyhow::{ensure, Context};
 use grenad::CompressionType;
 use rayon::ThreadPool;
 
 use crate::update::index_documents::{Transform, IndexDocumentsMethod};
 use crate::update::{ClearDocuments, IndexDocuments, UpdateIndexingStep};
+use crate::facet::FacetType;
 use crate::{Index, FieldsIdsMap};
 
 pub struct Settings<'a, 't, 'u, 'i> {
@@ -22,6 +26,7 @@ pub struct Settings<'a, 't, 'u, 'i> {
     // however if it is `Some(None)` it means that the user forced a reset of the setting.
     searchable_fields: Option<Option<Vec<String>>>,
     displayed_fields: Option<Option<Vec<String>>>,
+    faceted_fields: Option<HashMap<String, String>>,
 }
 
 impl<'a, 't, 'u, 'i> Settings<'a, 't, 'u, 'i> {
@@ -39,6 +44,7 @@ impl<'a, 't, 'u, 'i> Settings<'a, 't, 'u, 'i> {
             thread_pool: None,
             searchable_fields: None,
             displayed_fields: None,
+            faceted_fields: None,
         }
     }
 
@@ -58,71 +64,92 @@ impl<'a, 't, 'u, 'i> Settings<'a, 't, 'u, 'i> {
         self.displayed_fields = Some(Some(names));
     }
 
+    pub fn set_faceted_fields(&mut self, names_facet_types: HashMap<String, String>) {
+        self.faceted_fields = Some(names_facet_types);
+    }
+
     pub fn execute<F>(self, progress_callback: F) -> anyhow::Result<()>
     where
         F: Fn(UpdateIndexingStep) + Sync
     {
-        // Check that the searchable attributes have been specified.
-        if let Some(value) = self.searchable_fields {
-            let current_displayed_fields = self.index.displayed_fields(self.wtxn)?;
-            let current_fields_ids_map = self.index.fields_ids_map(self.wtxn)?;
+        let mut updated_searchable_fields = None;
+        let mut updated_faceted_fields = None;
+        let mut updated_displayed_fields = None;
 
-            let result = match value {
-                Some(fields_names) => {
-                    let mut fields_ids_map = current_fields_ids_map.clone();
-                    let searchable_fields: Vec<_> =
-                        fields_names.iter()
-                            .map(|name| fields_ids_map.insert(name))
-                            .collect::<Option<Vec<_>>>()
-                            .context("field id limit reached")?;
+        // Construct the new FieldsIdsMap based on the searchable fields order.
+        let fields_ids_map = self.index.fields_ids_map(self.wtxn)?;
+        let mut fields_ids_map = match self.searchable_fields {
+            Some(Some(searchable_fields)) => {
+                let mut new_fields_ids_map = FieldsIdsMap::new();
+                let mut new_searchable_fields = Vec::new();
 
-                    // If the searchable fields are ordered we don't have to generate a new `FieldsIdsMap`.
-                    if searchable_fields.windows(2).all(|win| win[0] < win[1]) {
-                        (
-                            fields_ids_map,
-                            Some(searchable_fields),
-                            current_displayed_fields.map(ToOwned::to_owned),
-                        )
-                    } else {
-                        // We create or generate the fields ids corresponding to those names.
-                        let mut fields_ids_map = FieldsIdsMap::new();
-                        let mut searchable_fields = Vec::new();
-                        for name in fields_names {
-                            let id = fields_ids_map.insert(&name).context("field id limit reached")?;
-                            searchable_fields.push(id);
-                        }
+                for name in searchable_fields {
+                    let id = new_fields_ids_map.insert(&name).context("field id limit reached")?;
+                    new_searchable_fields.push(id);
+                }
 
-                        // We complete the new FieldsIdsMap with the previous names.
-                        for (_id, name) in current_fields_ids_map.iter() {
-                            fields_ids_map.insert(name).context("field id limit reached")?;
-                        }
+                for (_, name) in fields_ids_map.iter() {
+                    new_fields_ids_map.insert(name).context("field id limit reached")?;
+                }
 
-                        // We must also update the displayed fields according to the new `FieldsIdsMap`.
-                        let displayed_fields = match current_displayed_fields {
-                            Some(fields) => {
-                                let mut displayed_fields = Vec::new();
-                                for id in fields {
-                                    let name = current_fields_ids_map.name(*id).unwrap();
-                                    let id = fields_ids_map.id(name).context("field id limit reached")?;
-                                    displayed_fields.push(id);
-                                }
-                                Some(displayed_fields)
-                            },
-                            None => None,
-                        };
+                updated_searchable_fields = Some(Some(new_searchable_fields));
+                new_fields_ids_map
+            },
+            Some(None) => {
+                updated_searchable_fields = Some(None);
+                fields_ids_map
+            },
+            None => fields_ids_map,
+        };
 
-                        (fields_ids_map, Some(searchable_fields), displayed_fields)
+        // We compute or generate the new primary key field id.
+        // TODO make the primary key settable.
+        let primary_key = match self.index.primary_key(&self.wtxn)? {
+            Some(id) => {
+                let current_fields_ids_map = self.index.fields_ids_map(self.wtxn)?;
+                let name = current_fields_ids_map.name(id).unwrap();
+                fields_ids_map.insert(name).context("field id limit reached")?
+            },
+            None => fields_ids_map.insert("id").context("field id limit reached")?,
+        };
+
+        if let Some(fields_names_facet_types) = self.faceted_fields {
+            let current_faceted_fields = self.index.faceted_fields(self.wtxn)?;
+
+            let mut faceted_fields = HashMap::new();
+            for (name, sftype) in fields_names_facet_types {
+                let ftype = FacetType::from_str(&sftype).with_context(|| format!("parsing facet type {:?}", sftype))?;
+                let id = fields_ids_map.insert(&name).context("field id limit reached")?;
+                match current_faceted_fields.get(&id) {
+                    Some(pftype) => {
+                        ensure!(ftype == *pftype, "{} facet type changed from {} to {}", name, ftype, pftype);
+                        faceted_fields.insert(id, ftype)
+                    },
+                    None => faceted_fields.insert(id, ftype),
+                };
+            }
+
+            updated_faceted_fields = Some(faceted_fields);
+        }
+
+        // Check that the displayed attributes have been specified.
+        if let Some(value) = self.displayed_fields {
+            match value {
+                Some(names) => {
+                    let mut new_displayed_fields = Vec::new();
+                    for name in names {
+                        let id = fields_ids_map.insert(&name).context("field id limit reached")?;
+                        new_displayed_fields.push(id);
                     }
-                },
-                None => (
-                    current_fields_ids_map.clone(),
-                    None,
-                    current_displayed_fields.map(ToOwned::to_owned),
-                ),
-            };
-
-            let (mut fields_ids_map, searchable_fields, displayed_fields) = result;
+                    updated_displayed_fields = Some(Some(new_displayed_fields));
+                }
+                None => updated_displayed_fields = Some(None),
+            }
+        }
 
+        // If any setting have modified any of the datastructures it means that we need
+        // to retrieve the documents and then reindex then with the new settings.
+        if updated_searchable_fields.is_some() || updated_faceted_fields.is_some() {
             let transform = Transform {
                 rtxn: &self.wtxn,
                 index: self.index,
@@ -136,15 +163,6 @@ impl<'a, 't, 'u, 'i> Settings<'a, 't, 'u, 'i> {
                 autogenerate_docids: false,
             };
 
-            // We compute or generate the new primary key field id.
-            let primary_key = match self.index.primary_key(&self.wtxn)? {
-                Some(id) => {
-                    let name = current_fields_ids_map.name(id).unwrap();
-                    fields_ids_map.insert(name).context("field id limit reached")?
-                },
-                None => fields_ids_map.insert("id").context("field id limit reached")?,
-            };
-
             // We remap the documents fields based on the new `FieldsIdsMap`.
             let output = transform.remap_index_documents(primary_key, fields_ids_map.clone())?;
 
@@ -152,18 +170,18 @@ impl<'a, 't, 'u, 'i> Settings<'a, 't, 'u, 'i> {
             // this way next indexing methods will be based on that.
             self.index.put_fields_ids_map(self.wtxn, &fields_ids_map)?;
 
-            // The new searchable fields are also written down to make sure
-            // that the IndexDocuments system takes only these ones into account.
-            match searchable_fields {
-                Some(fields) => self.index.put_searchable_fields(self.wtxn, &fields)?,
-                None => self.index.delete_searchable_fields(self.wtxn).map(drop)?,
+            if let Some(faceted_fields) = updated_faceted_fields {
+                // We write the faceted_fields fields into the database here.
+                self.index.put_faceted_fields(self.wtxn, &faceted_fields)?;
             }
 
-            // We write the displayed fields into the database here
-            // to make sure that the right fields are displayed.
-            match displayed_fields {
-                Some(fields) => self.index.put_displayed_fields(self.wtxn, &fields)?,
-                None => self.index.delete_displayed_fields(self.wtxn).map(drop)?,
+            if let Some(searchable_fields) = updated_searchable_fields {
+                // The new searchable fields are also written down to make sure
+                // that the IndexDocuments system takes only these ones into account.
+                match searchable_fields {
+                    Some(fields) => self.index.put_searchable_fields(self.wtxn, &fields)?,
+                    None => self.index.delete_searchable_fields(self.wtxn).map(drop)?,
+                }
             }
 
             // We clear the full database (words-fst, documents ids and documents content).
@@ -180,33 +198,15 @@ impl<'a, 't, 'u, 'i> Settings<'a, 't, 'u, 'i> {
             indexing_builder.chunk_compression_level = self.chunk_compression_level;
             indexing_builder.chunk_fusing_shrink_size = self.chunk_fusing_shrink_size;
             indexing_builder.thread_pool = self.thread_pool;
-            indexing_builder.execute_raw(output, progress_callback)?;
+            indexing_builder.execute_raw(output, &progress_callback)?;
         }
 
-        // Check that the displayed attributes have been specified.
-        if let Some(value) = self.displayed_fields {
-            match value {
-                // If it has been set, and it was a list of fields names, we create
-                // or generate the fields ids corresponds to those names and store them
-                // in the database in the order they were specified.
-                Some(fields_names) => {
-                    let mut fields_ids_map = self.index.fields_ids_map(self.wtxn)?;
-
-                    // We create or generate the fields ids corresponding to those names.
-                    let mut fields_ids = Vec::new();
-                    for name in fields_names {
-                        let id = fields_ids_map.insert(&name).context("field id limit reached")?;
-                        fields_ids.push(id);
-                    }
-
-                    self.index.put_displayed_fields(self.wtxn, &fields_ids)?;
-                },
-                // If it was set to `null` it means that the user wants to get the default behavior
-                // which is displaying all the attributes in no specific order (FieldsIdsMap order),
-                // we just have to delete the displayed fields.
-                None => {
-                    self.index.delete_displayed_fields(self.wtxn)?;
-                },
+        if let Some(displayed_fields) = updated_displayed_fields {
+            // We write the displayed fields into the database here
+            // to make sure that the right fields are displayed.
+            match displayed_fields {
+                Some(fields) => self.index.put_displayed_fields(self.wtxn, &fields)?,
+                None => self.index.delete_displayed_fields(self.wtxn).map(drop)?,
             }
         }
 
@@ -219,6 +219,7 @@ mod tests {
     use super::*;
     use crate::update::{IndexDocuments, UpdateFormat};
     use heed::EnvOpenOptions;
+    use maplit::hashmap;
 
     #[test]
     fn set_and_reset_searchable_fields() {
@@ -386,4 +387,31 @@ mod tests {
         assert_eq!(fields_ids, None);
         drop(rtxn);
     }
+
+    #[test]
+    fn set_faceted_fields() {
+        let path = tempfile::tempdir().unwrap();
+        let mut options = EnvOpenOptions::new();
+        options.map_size(10 * 1024 * 1024); // 10 MB
+        let index = Index::new(options, &path).unwrap();
+
+        // Set the faceted fields to be the age.
+        let mut wtxn = index.write_txn().unwrap();
+        let mut builder = Settings::new(&mut wtxn, &index);
+        builder.set_faceted_fields(hashmap!{ "age".into() => "integer".into() });
+        builder.execute(|_| ()).unwrap();
+
+        // Then index some documents.
+        let content = &b"name,age\nkevin,23\nkevina,21\nbenoit,34\n"[..];
+        let mut builder = IndexDocuments::new(&mut wtxn, &index);
+        builder.update_format(UpdateFormat::Csv);
+        builder.execute(content, |_| ()).unwrap();
+        wtxn.commit().unwrap();
+
+        // Check that the displayed fields are correctly set.
+        let rtxn = index.read_txn().unwrap();
+        let fields_ids = index.faceted_fields(&rtxn).unwrap();
+        assert_eq!(fields_ids, hashmap!{ 1 => FacetType::Integer });
+        drop(rtxn);
+    }
 }