Merge #368

368: Remove limit of 1000 position per attribute r=irevoire a=ManyTheFish

Instead of using an arbitrary limit we encode the absolute position in a u32
using one strong u16 for the field id and a weak u16 for the relative position in the attribute.

- [x] check database size difference

below is the database size difference for each dataset:
![Capture d’écran 2021-09-27 à 18 01 44](https://user-images.githubusercontent.com/6482087/134944199-bd25fed0-6c34-475c-9afc-197871e06553.png)

- [ ] check search time on big dataset


Related to [product#202](https://github.com/meilisearch/product/issues/202)

Co-authored-by: many <maxime@meilisearch.com>

http-ui/src/main.rs

@@ -131,6 +131,11 @@ pub struct IndexerOpt {
     /// Number of parallel jobs for indexing, defaults to # of CPUs.
     #[structopt(long)]
     pub indexing_jobs: Option<usize>,
+
+    /// Maximum relative position in an attribute for a word to be indexed.
+    /// Any value higher than 65535 will be clamped.
+    #[structopt(long)]
+    pub max_positions_per_attributes: Option<u32>,
 }
 
 struct Highlighter<'a, A> {
@@ -346,6 +351,9 @@ async fn main() -> anyhow::Result<()> {
             if let Some(chunk_compression_level) = indexer_opt_cloned.chunk_compression_level {
                 update_builder.chunk_compression_level(chunk_compression_level);
             }
+            if let Some(max_pos_per_attributes) = indexer_opt_cloned.max_positions_per_attributes {
+                update_builder.max_positions_per_attributes(max_pos_per_attributes);
+            }
             update_builder.thread_pool(GLOBAL_THREAD_POOL.get().unwrap());
             update_builder.log_every_n(indexer_opt_cloned.log_every_n);
             update_builder.max_memory(indexer_opt_cloned.max_memory.get_bytes() as usize);

milli/src/lib.rs

@@ -53,9 +53,24 @@ pub type Attribute = u32;
 pub type DocumentId = u32;
 pub type FieldId = u16;
 pub type Position = u32;
+pub type RelativePosition = u16;
 pub type FieldDistribution = BTreeMap<String, u64>;
 pub type GeoPoint = rstar::primitives::GeomWithData<[f64; 2], DocumentId>;
 
+pub const MAX_POSITION_PER_ATTRIBUTE: u32 = u16::MAX as u32 + 1;
+
+// Convert an absolute word position into a relative position.
+// Return the field id of the attribute related to the absolute position
+// and the relative position in the attribute.
+pub fn relative_from_absolute_position(absolute: Position) -> (FieldId, RelativePosition) {
+    ((absolute >> 16) as u16, (absolute & 0xFFFF) as u16)
+}
+
+// Compute the absolute word position with the field id of the attribute and relative position in the attribute.
+pub fn absolute_from_relative_position(field_id: FieldId, relative: RelativePosition) -> Position {
+    (field_id as u32) << 16 | (relative as u32)
+}
+
 /// Transform a raw obkv store into a JSON Object.
 pub fn obkv_to_json(
     displayed_fields: &[FieldId],
@@ -187,4 +202,26 @@ mod tests {
         // the distance of hard separators is clamped to 8 anyway.
         assert_eq!(string, "name: John Doe. . 43. hello. I. am. fine. . ");
     }
+
+    #[test]
+    fn test_relative_position_conversion() {
+        assert_eq!((0x0000, 0x0000), relative_from_absolute_position(0x00000000));
+        assert_eq!((0x0000, 0xFFFF), relative_from_absolute_position(0x0000FFFF));
+        assert_eq!((0xFFFF, 0x0000), relative_from_absolute_position(0xFFFF0000));
+        assert_eq!((0xFF00, 0xFF00), relative_from_absolute_position(0xFF00FF00));
+        assert_eq!((0xFF00, 0x00FF), relative_from_absolute_position(0xFF0000FF));
+        assert_eq!((0x1234, 0x5678), relative_from_absolute_position(0x12345678));
+        assert_eq!((0xFFFF, 0xFFFF), relative_from_absolute_position(0xFFFFFFFF));
+    }
+
+    #[test]
+    fn test_absolute_position_conversion() {
+        assert_eq!(0x00000000, absolute_from_relative_position(0x0000, 0x0000));
+        assert_eq!(0x0000FFFF, absolute_from_relative_position(0x0000, 0xFFFF));
+        assert_eq!(0xFFFF0000, absolute_from_relative_position(0xFFFF, 0x0000));
+        assert_eq!(0xFF00FF00, absolute_from_relative_position(0xFF00, 0xFF00));
+        assert_eq!(0xFF0000FF, absolute_from_relative_position(0xFF00, 0x00FF));
+        assert_eq!(0x12345678, absolute_from_relative_position(0x1234, 0x5678));
+        assert_eq!(0xFFFFFFFF, absolute_from_relative_position(0xFFFF, 0xFFFF));
+    }
 }

milli/src/proximity.rs

@@ -1,8 +1,7 @@
 use std::cmp;
 
-use crate::{Attribute, Position};
+use crate::{relative_from_absolute_position, Position};
 
-pub const ONE_ATTRIBUTE: u32 = 1000;
 pub const MAX_DISTANCE: u32 = 8;
 
 pub fn index_proximity(lhs: u32, rhs: u32) -> u32 {
@@ -14,19 +13,15 @@ pub fn index_proximity(lhs: u32, rhs: u32) -> u32 {
 }
 
 pub fn positions_proximity(lhs: Position, rhs: Position) -> u32 {
-    let (lhs_attr, lhs_index) = extract_position(lhs);
+    let (lhs_attr, lhs_index) = relative_from_absolute_position(lhs);
-    let (rhs_attr, rhs_index) = extract_position(rhs);
+    let (rhs_attr, rhs_index) = relative_from_absolute_position(rhs);
     if lhs_attr != rhs_attr {
         MAX_DISTANCE
     } else {
-        index_proximity(lhs_index, rhs_index)
+        index_proximity(lhs_index as u32, rhs_index as u32)
     }
 }
 
-pub fn extract_position(position: Position) -> (Attribute, Position) {
-    (position / ONE_ATTRIBUTE, position % ONE_ATTRIBUTE)
-}
-
 pub fn path_proximity(path: &[Position]) -> u32 {
     path.windows(2).map(|w| positions_proximity(w[0], w[1])).sum::<u32>()
 }

milli/src/search/criteria/exactness.rs

@@ -10,7 +10,7 @@ use crate::search::criteria::{
     resolve_query_tree, Context, Criterion, CriterionParameters, CriterionResult,
 };
 use crate::search::query_tree::{Operation, PrimitiveQueryPart};
-use crate::Result;
+use crate::{absolute_from_relative_position, FieldId, Result};
 
 pub struct Exactness<'t> {
     ctx: &'t dyn Context<'t>,
@@ -181,7 +181,7 @@ fn resolve_state(
                         ctx.field_id_word_count_docids(id, query_len)?
                     {
                         let mut attribute_candidates_array =
-                            attribute_start_with_docids(ctx, id as u32, query)?;
+                            attribute_start_with_docids(ctx, id, query)?;
                         attribute_candidates_array.push(attribute_allowed_docids);
                         candidates |= intersection_of(attribute_candidates_array.iter().collect());
                     }
@@ -199,8 +199,7 @@ fn resolve_state(
             let mut candidates = RoaringBitmap::new();
             let attributes_ids = ctx.searchable_fields_ids()?;
             for id in attributes_ids {
-                let attribute_candidates_array =
+                let attribute_candidates_array = attribute_start_with_docids(ctx, id, query)?;
-                    attribute_start_with_docids(ctx, id as u32, query)?;
                 candidates |= intersection_of(attribute_candidates_array.iter().collect());
             }
 
@@ -290,12 +289,12 @@ fn resolve_state(
 
 fn attribute_start_with_docids(
     ctx: &dyn Context,
-    attribute_id: u32,
+    attribute_id: FieldId,
     query: &[ExactQueryPart],
 ) -> heed::Result<Vec<RoaringBitmap>> {
     let mut attribute_candidates_array = Vec::new();
     // start from attribute first position
-    let mut pos = attribute_id * 1000;
+    let mut pos = absolute_from_relative_position(attribute_id, 0);
     for part in query {
         use ExactQueryPart::*;
         match part {

milli/src/update/index_documents/extract/extract_docid_word_positions.rs

@@ -10,8 +10,7 @@ use serde_json::Value;
 
 use super::helpers::{concat_u32s_array, create_sorter, sorter_into_reader, GrenadParameters};
 use crate::error::{InternalError, SerializationError};
-use crate::proximity::ONE_ATTRIBUTE;
+use crate::{absolute_from_relative_position, FieldId, Result, MAX_POSITION_PER_ATTRIBUTE};
-use crate::{FieldId, Result};
 
 /// Extracts the word and positions where this word appear and
 /// prefixes it by the document id.
@@ -24,7 +23,10 @@ pub fn extract_docid_word_positions<R: io::Read>(
     indexer: GrenadParameters,
     searchable_fields: &Option<HashSet<FieldId>>,
     stop_words: Option<&fst::Set<&[u8]>>,
+    max_positions_per_attributes: Option<u32>,
 ) -> Result<(RoaringBitmap, grenad::Reader<File>)> {
+    let max_positions_per_attributes = max_positions_per_attributes
+        .map_or(MAX_POSITION_PER_ATTRIBUTE, |max| max.min(MAX_POSITION_PER_ATTRIBUTE));
     let max_memory = indexer.max_memory_by_thread();
 
     let mut documents_ids = RoaringBitmap::new();
@@ -63,7 +65,7 @@ pub fn extract_docid_word_positions<R: io::Read>(
                 if let Some(field) = json_to_string(&value, &mut field_buffer) {
                     let analyzed = analyzer.analyze(field);
                     let tokens = process_tokens(analyzed.tokens())
-                        .take_while(|(p, _)| (*p as u32) < ONE_ATTRIBUTE);
+                        .take_while(|(p, _)| (*p as u32) < max_positions_per_attributes);
 
                     for (index, token) in tokens {
                         let token = token.text().trim();
@@ -71,10 +73,10 @@ pub fn extract_docid_word_positions<R: io::Read>(
                             key_buffer.truncate(mem::size_of::<u32>());
                             key_buffer.extend_from_slice(token.as_bytes());
 
-                            let position: u32 = index
+                            let position: u16 = index
                                 .try_into()
                                 .map_err(|_| SerializationError::InvalidNumberSerialization)?;
-                            let position = field_id as u32 * ONE_ATTRIBUTE + position;
+                            let position = absolute_from_relative_position(field_id, position);
                             docid_word_positions_sorter
                                 .insert(&key_buffer, &position.to_ne_bytes())?;
                         }

milli/src/update/index_documents/extract/extract_fid_word_count_docids.rs

@@ -10,8 +10,7 @@ use super::helpers::{
 };
 use crate::error::SerializationError;
 use crate::index::db_name::DOCID_WORD_POSITIONS;
-use crate::proximity::extract_position;
+use crate::{relative_from_absolute_position, DocumentId, FieldId, Result};
-use crate::{DocumentId, FieldId, Result};
 
 /// Extracts the field id word count and the documents ids where
 /// this field id with this amount of words appear.
@@ -53,8 +52,8 @@ pub fn extract_fid_word_count_docids<R: io::Read>(
         }
 
         for position in read_u32_ne_bytes(value) {
-            let (field_id, position) = extract_position(position);
+            let (field_id, position) = relative_from_absolute_position(position);
-            let word_count = position + 1;
+            let word_count = position as u32 + 1;
 
             let value = document_fid_wordcount.entry(field_id as FieldId).or_insert(0);
             *value = cmp::max(*value, word_count);

milli/src/update/index_documents/extract/mod.rs

@@ -42,6 +42,7 @@ pub(crate) fn data_from_obkv_documents(
     primary_key_id: FieldId,
     geo_field_id: Option<FieldId>,
     stop_words: Option<fst::Set<&[u8]>>,
+    max_positions_per_attributes: Option<u32>,
 ) -> Result<()> {
     let result: Result<(Vec<_>, (Vec<_>, Vec<_>))> = obkv_chunks
         .par_bridge()
@@ -55,6 +56,7 @@ pub(crate) fn data_from_obkv_documents(
                 primary_key_id,
                 geo_field_id,
                 &stop_words,
+                max_positions_per_attributes,
             )
         })
         .collect();
@@ -177,6 +179,7 @@ fn extract_documents_data(
     primary_key_id: FieldId,
     geo_field_id: Option<FieldId>,
     stop_words: &Option<fst::Set<&[u8]>>,
+    max_positions_per_attributes: Option<u32>,
 ) -> Result<(
     grenad::Reader<CursorClonableMmap>,
     (grenad::Reader<CursorClonableMmap>, grenad::Reader<CursorClonableMmap>),
@@ -206,6 +209,7 @@ fn extract_documents_data(
                     indexer.clone(),
                     searchable_fields,
                     stop_words.as_ref(),
+                    max_positions_per_attributes,
                 )?;
 
                 // send documents_ids to DB writer

milli/src/update/index_documents/mod.rs

@@ -68,6 +68,7 @@ pub struct IndexDocuments<'t, 'u, 'i, 'a> {
     pub(crate) chunk_compression_type: CompressionType,
     pub(crate) chunk_compression_level: Option<u32>,
     pub(crate) thread_pool: Option<&'a ThreadPool>,
+    pub(crate) max_positions_per_attributes: Option<u32>,
     facet_level_group_size: Option<NonZeroUsize>,
     facet_min_level_size: Option<NonZeroUsize>,
     words_prefix_threshold: Option<u32>,
@@ -104,6 +105,7 @@ impl<'t, 'u, 'i, 'a> IndexDocuments<'t, 'u, 'i, 'a> {
             update_method: IndexDocumentsMethod::ReplaceDocuments,
             autogenerate_docids: false,
             update_id,
+            max_positions_per_attributes: None,
         }
     }
 
@@ -262,6 +264,7 @@ impl<'t, 'u, 'i, 'a> IndexDocuments<'t, 'u, 'i, 'a> {
                     primary_key_id,
                     geo_field_id,
                     stop_words,
+                    self.max_positions_per_attributes,
                 )
             });
 
@@ -284,6 +287,7 @@ impl<'t, 'u, 'i, 'a> IndexDocuments<'t, 'u, 'i, 'a> {
                 chunk_compression_type: self.chunk_compression_type,
                 chunk_compression_level: self.chunk_compression_level,
                 thread_pool: self.thread_pool,
+                max_positions_per_attributes: self.max_positions_per_attributes,
                 update_id: self.update_id,
             };
             let mut deletion_builder = update_builder.delete_documents(self.wtxn, self.index)?;
@@ -884,6 +888,44 @@ mod tests {
         wtxn.commit().unwrap();
     }
 
+    #[test]
+    fn index_more_than_1000_positions_in_a_field() {
+        let path = tempfile::tempdir().unwrap();
+        let mut options = EnvOpenOptions::new();
+        options.map_size(50 * 1024 * 1024); // 10 MB
+        let index = Index::new(options, &path).unwrap();
+
+        let mut wtxn = index.write_txn().unwrap();
+
+        let mut big_object = HashMap::new();
+        big_object.insert(S("id"), "wow");
+        let content: String =
+            (0..=u16::MAX).into_iter().map(|p| p.to_string()).reduce(|a, b| a + " " + &b).unwrap();
+        big_object.insert("content".to_string(), &content);
+
+        let mut cursor = Cursor::new(Vec::new());
+
+        let mut builder = DocumentBatchBuilder::new(&mut cursor).unwrap();
+        builder.add_documents(big_object).unwrap();
+        builder.finish().unwrap();
+        cursor.set_position(0);
+        let content = DocumentBatchReader::from_reader(cursor).unwrap();
+
+        let builder = IndexDocuments::new(&mut wtxn, &index, 0);
+        builder.execute(content, |_, _| ()).unwrap();
+
+        wtxn.commit().unwrap();
+
+        let mut rtxn = index.read_txn().unwrap();
+
+        assert!(index.word_docids.get(&mut rtxn, "0").unwrap().is_some());
+        assert!(index.word_docids.get(&mut rtxn, "64").unwrap().is_some());
+        assert!(index.word_docids.get(&mut rtxn, "256").unwrap().is_some());
+        assert!(index.word_docids.get(&mut rtxn, "1024").unwrap().is_some());
+        assert!(index.word_docids.get(&mut rtxn, "32768").unwrap().is_some());
+        assert!(index.word_docids.get(&mut rtxn, "65535").unwrap().is_some());
+    }
+
     #[test]
     fn index_documents_with_zeroes() {
         let path = tempfile::tempdir().unwrap();

milli/src/update/settings.rs

@@ -69,6 +69,7 @@ pub struct Settings<'a, 't, 'u, 'i> {
     pub(crate) chunk_compression_type: CompressionType,
     pub(crate) chunk_compression_level: Option<u32>,
     pub(crate) thread_pool: Option<&'a ThreadPool>,
+    pub(crate) max_positions_per_attributes: Option<u32>,
     update_id: u64,
 
     searchable_fields: Setting<Vec<String>>,
@@ -108,6 +109,7 @@ impl<'a, 't, 'u, 'i> Settings<'a, 't, 'u, 'i> {
             synonyms: Setting::NotSet,
             primary_key: Setting::NotSet,
             update_id,
+            max_positions_per_attributes: None,
         }
     }
 
@@ -237,6 +239,7 @@ impl<'a, 't, 'u, 'i> Settings<'a, 't, 'u, 'i> {
         indexing_builder.chunk_compression_type = self.chunk_compression_type;
         indexing_builder.chunk_compression_level = self.chunk_compression_level;
         indexing_builder.thread_pool = self.thread_pool;
+        indexing_builder.max_positions_per_attributes = self.max_positions_per_attributes;
         indexing_builder.execute_raw(output, &cb)?;
 
         Ok(())

milli/src/update/update_builder.rs

@@ -12,6 +12,7 @@ pub struct UpdateBuilder<'a> {
     pub(crate) chunk_compression_type: CompressionType,
     pub(crate) chunk_compression_level: Option<u32>,
     pub(crate) thread_pool: Option<&'a ThreadPool>,
+    pub(crate) max_positions_per_attributes: Option<u32>,
     pub(crate) update_id: u64,
 }
 
@@ -25,6 +26,7 @@ impl<'a> UpdateBuilder<'a> {
             chunk_compression_type: CompressionType::None,
             chunk_compression_level: None,
             thread_pool: None,
+            max_positions_per_attributes: None,
             update_id,
         }
     }
@@ -57,6 +59,10 @@ impl<'a> UpdateBuilder<'a> {
         self.thread_pool = Some(thread_pool);
     }
 
+    pub fn max_positions_per_attributes(&mut self, max_positions_per_attributes: u32) {
+        self.max_positions_per_attributes = Some(max_positions_per_attributes);
+    }
+
     pub fn clear_documents<'t, 'u, 'i>(
         self,
         wtxn: &'t mut heed::RwTxn<'i, 'u>,
@@ -87,6 +93,7 @@ impl<'a> UpdateBuilder<'a> {
         builder.chunk_compression_type = self.chunk_compression_type;
         builder.chunk_compression_level = self.chunk_compression_level;
         builder.thread_pool = self.thread_pool;
+        builder.max_positions_per_attributes = self.max_positions_per_attributes;
 
         builder
     }
@@ -105,6 +112,7 @@ impl<'a> UpdateBuilder<'a> {
         builder.chunk_compression_type = self.chunk_compression_type;
         builder.chunk_compression_level = self.chunk_compression_level;
         builder.thread_pool = self.thread_pool;
+        builder.max_positions_per_attributes = self.max_positions_per_attributes;
 
         builder
     }