Remove the FacetValueStringCodec

milli/src/search/facet/facet_distribution.rs

@@ -1,6 +1,6 @@
 use std::collections::{BTreeMap, HashSet};
 use std::ops::Bound::Unbounded;
-use std::{cmp, fmt};
+use std::{cmp, fmt, mem};
 
 use heed::types::{ByteSlice, Unit};
 use heed::{BytesDecode, Database};
@@ -8,7 +8,7 @@ use roaring::RoaringBitmap;
 
 use crate::error::{FieldIdMapMissingEntry, UserError};
 use crate::facet::FacetType;
-use crate::heed_codec::facet::FacetValueStringCodec;
+use crate::heed_codec::facet::FacetStringLevelZeroCodec;
 use crate::search::facet::{FacetNumberIter, FacetNumberRange};
 use crate::{DocumentId, FieldId, Index, Result};
 
@@ -81,7 +81,7 @@ impl<'a> FacetDistribution<'a> {
             let mut key_buffer: Vec<_> = field_id.to_be_bytes().iter().copied().collect();
 
             for docid in candidates.into_iter().take(CANDIDATES_THRESHOLD as usize) {
-                key_buffer.truncate(1);
+                key_buffer.truncate(mem::size_of::<FieldId>());
                 key_buffer.extend_from_slice(&docid.to_be_bytes());
                 let iter = db
                     .remap_key_type::<ByteSlice>()
@@ -158,7 +158,7 @@ impl<'a> FacetDistribution<'a> {
             .facet_id_string_docids
             .remap_key_type::<ByteSlice>()
             .prefix_iter(self.rtxn, &field_id.to_be_bytes())?
-            .remap_key_type::<FacetValueStringCodec>();
+            .remap_key_type::<FacetStringLevelZeroCodec>();
 
         for result in iter {
             let ((_, value), docids) = result?;

milli/src/search/facet/facet_string.rs

@@ -130,7 +130,7 @@ use std::ops::Bound;
 use std::ops::Bound::{Excluded, Included, Unbounded};
 
 use either::{Either, Left, Right};
-use heed::types::{ByteSlice, DecodeIgnore, Str};
+use heed::types::{ByteSlice, DecodeIgnore};
 use heed::{Database, LazyDecode, RoRange};
 use roaring::RoaringBitmap;
 
@@ -298,10 +298,10 @@ impl<'t> FacetStringIter<'t> {
     ) -> heed::Result<Option<u8>> {
         Ok(db
             .remap_types::<ByteSlice, DecodeIgnore>()
-            .prefix_iter(rtxn, &[fid][..])? // the field id is the first bit
+            .prefix_iter(rtxn, &fid.to_be_bytes())? // the field id is the first two bits
             .last()
             .transpose()?
-            .map(|(key_bytes, _)| key_bytes[1])) // the level is the second bit
+            .map(|(key_bytes, _)| key_bytes[2])) // the level is the third bit
     }
 }
 

milli/src/search/facet/filter_condition.rs

@@ -17,7 +17,7 @@ use self::Operator::*;
 use super::parser::{FilterParser, Rule, PREC_CLIMBER};
 use super::FacetNumberRange;
 use crate::error::UserError;
-use crate::heed_codec::facet::{FacetLevelValueF64Codec, FacetValueStringCodec};
+use crate::heed_codec::facet::{FacetLevelValueF64Codec, FacetStringLevelZeroCodec};
 use crate::{CboRoaringBitmapCodec, FieldId, FieldsIdsMap, Index, Result};
 
 #[derive(Debug, Clone, PartialEq)]
@@ -363,7 +363,7 @@ impl FilterCondition {
         rtxn: &heed::RoTxn,
         index: &Index,
         numbers_db: heed::Database<FacetLevelValueF64Codec, CboRoaringBitmapCodec>,
-        strings_db: heed::Database<FacetValueStringCodec, CboRoaringBitmapCodec>,
+        strings_db: heed::Database<FacetStringLevelZeroCodec, CboRoaringBitmapCodec>,
         field_id: FieldId,
         operator: &Operator,
     ) -> Result<RoaringBitmap> {