Fix and optimize word_prefix_pair_proximity_docids database

infos/src/main.rs

@@ -207,6 +207,24 @@ enum Command {
         word2: String,
     },
 
+    /// Outputs a CSV with the proximities for the two specified words and
+    /// the documents ids where these relations appears.
+    ///
+    /// `word1`, `prefix` defines the word pair specified *in this specific order*.
+    /// `proximity` defines the proximity between the two specified words.
+    /// `documents_ids` defines the documents ids where the relation appears.
+    WordPrefixPairProximitiesDocids {
+        /// Display the whole documents ids in details.
+        #[structopt(long)]
+        full_display: bool,
+
+        /// First word of the word pair.
+        word1: String,
+
+        /// Second word of the word pair.
+        prefix: String,
+    },
+
     /// Outputs the words FST to standard output.
     ///
     /// One can use the FST binary helper to dissect and analyze it,
@@ -282,6 +300,9 @@ fn main() -> anyhow::Result<()> {
         WordPairProximitiesDocids { full_display, word1, word2 } => {
             word_pair_proximities_docids(&index, &rtxn, !full_display, word1, word2)
         }
+        WordPrefixPairProximitiesDocids { full_display, word1, prefix } => {
+            word_prefix_pair_proximities_docids(&index, &rtxn, !full_display, word1, prefix)
+        }
         ExportWordsFst => export_words_fst(&index, &rtxn),
         ExportWordsPrefixFst => export_words_prefix_fst(&index, &rtxn),
         ExportDocuments { internal_documents_ids } => {
@@ -1131,3 +1152,46 @@ fn word_pair_proximities_docids(
 
     Ok(wtr.flush()?)
 }
+
+fn word_prefix_pair_proximities_docids(
+    index: &Index,
+    rtxn: &heed::RoTxn,
+    debug: bool,
+    word1: String,
+    word_prefix: String,
+) -> anyhow::Result<()> {
+    use heed::types::ByteSlice;
+    use milli::RoaringBitmapCodec;
+
+    let stdout = io::stdout();
+    let mut wtr = csv::Writer::from_writer(stdout.lock());
+    wtr.write_record(&["word1", "word_prefix", "proximity", "documents_ids"])?;
+
+    // Create the prefix key with only the pair of words.
+    let mut prefix = Vec::with_capacity(word1.len() + word_prefix.len() + 1);
+    prefix.extend_from_slice(word1.as_bytes());
+    prefix.push(0);
+    prefix.extend_from_slice(word_prefix.as_bytes());
+
+    let db = index.word_prefix_pair_proximity_docids.as_polymorph();
+    let iter = db.prefix_iter::<_, ByteSlice, RoaringBitmapCodec>(rtxn, &prefix)?;
+    for result in iter {
+        let (key, docids) = result?;
+
+        // Skip keys that are longer than the requested one,
+        // a longer key means that the second word is a prefix of the request word.
+        if key.len() != prefix.len() + 1 {
+            continue;
+        }
+
+        let proximity = key.last().unwrap();
+        let docids = if debug {
+            format!("{:?}", docids)
+        } else {
+            format!("{:?}", docids.iter().collect::<Vec<_>>())
+        };
+        wtr.write_record(&[&word1, &word_prefix, &proximity.to_string(), &docids])?;
+    }
+
+    Ok(wtr.flush()?)
+}

milli/src/search/criteria/exactness.rs

@@ -180,10 +180,6 @@ fn resolve_state(
                     if let Some(attribute_allowed_docids) =
                         ctx.field_id_word_count_docids(id, query_len)?
                     {
-                        println!(
-                            "found candidates that have the good count: {:?}",
-                            attribute_allowed_docids
-                        );
                         let mut attribute_candidates_array =
                             attribute_start_with_docids(ctx, id as u32, query)?;
                         attribute_candidates_array.push(attribute_allowed_docids);

milli/src/search/criteria/mod.rs

@@ -461,13 +461,18 @@ fn query_pair_proximity_docids(
     let prefix = right.prefix;
     match (&left.kind, &right.kind) {
         (QueryKind::Exact { word: left, .. }, QueryKind::Exact { word: right, .. }) => {
-            if prefix && ctx.in_prefix_cache(&right) {
-                Ok(ctx
-                    .word_prefix_pair_proximity_docids(left.as_str(), right.as_str(), proximity)?
-                    .unwrap_or_default())
-            } else if prefix {
+            if prefix {
+                match ctx.word_prefix_pair_proximity_docids(
+                    left.as_str(),
+                    right.as_str(),
+                    proximity,
+                )? {
+                    Some(docids) => Ok(docids),
+                    None => {
                         let r_words = word_derivations(&right, true, 0, ctx.words_fst(), wdcache)?;
                         all_word_pair_proximity_docids(ctx, &[(left, 0)], &r_words, proximity)
+                    }
+                }
             } else {
                 Ok(ctx
                     .word_pair_proximity_docids(left.as_str(), right.as_str(), proximity)?
@@ -477,22 +482,24 @@ fn query_pair_proximity_docids(
         (QueryKind::Tolerant { typo, word: left }, QueryKind::Exact { word: right, .. }) => {
             let l_words =
                 word_derivations(&left, false, *typo, ctx.words_fst(), wdcache)?.to_owned();
-            if prefix && ctx.in_prefix_cache(&right) {
+            if prefix {
                 let mut docids = RoaringBitmap::new();
                 for (left, _) in l_words {
-                    let current_docids = ctx
-                        .word_prefix_pair_proximity_docids(
-                            left.as_ref(),
-                            right.as_ref(),
+                    let current_docids = match ctx.word_prefix_pair_proximity_docids(
+                        left.as_str(),
+                        right.as_str(),
                         proximity,
-                        )?
-                        .unwrap_or_default();
+                    )? {
+                        Some(docids) => Ok(docids),
+                        None => {
+                            let r_words =
+                                word_derivations(&right, true, 0, ctx.words_fst(), wdcache)?;
+                            all_word_pair_proximity_docids(ctx, &[(left, 0)], &r_words, proximity)
+                        }
+                    }?;
                     docids |= current_docids;
                 }
                 Ok(docids)
-            } else if prefix {
-                let r_words = word_derivations(&right, true, 0, ctx.words_fst(), wdcache)?;
-                all_word_pair_proximity_docids(ctx, &l_words, &r_words, proximity)
             } else {
                 all_word_pair_proximity_docids(ctx, &l_words, &[(right, 0)], proximity)
             }

milli/src/update/index_documents/mod.rs

@@ -21,7 +21,7 @@ use typed_chunk::{write_typed_chunk_into_index, TypedChunk};
 
 pub use self::helpers::{
     create_sorter, create_writer, merge_cbo_roaring_bitmaps, merge_roaring_bitmaps,
-    sorter_into_lmdb_database, write_into_lmdb_database, writer_into_reader,
+    sorter_into_lmdb_database, write_into_lmdb_database, writer_into_reader, MergeFn,
 };
 use self::helpers::{grenad_obkv_into_chunks, GrenadParameters};
 pub use self::transform::{Transform, TransformOutput};
@@ -81,7 +81,7 @@ pub struct IndexDocuments<'t, 'u, 'i, 'a> {
     pub(crate) thread_pool: Option<&'a ThreadPool>,
     facet_level_group_size: Option<NonZeroUsize>,
     facet_min_level_size: Option<NonZeroUsize>,
-    words_prefix_threshold: Option<f64>,
+    words_prefix_threshold: Option<u32>,
     max_prefix_length: Option<usize>,
     words_positions_level_group_size: Option<NonZeroU32>,
     words_positions_min_level_size: Option<NonZeroU32>,

milli/src/update/word_prefix_pair_proximity_docids.rs

@@ -1,15 +1,13 @@
-use std::str;
+use std::collections::HashMap;
 
-use fst::automaton::{Automaton, Str};
-use fst::{IntoStreamer, Streamer};
+use fst::IntoStreamer;
 use grenad::CompressionType;
 use heed::types::ByteSlice;
-use heed::BytesEncode;
 use log::debug;
+use slice_group_by::GroupBy;
 
-use crate::heed_codec::StrStrU8Codec;
 use crate::update::index_documents::{
-    create_sorter, merge_cbo_roaring_bitmaps, sorter_into_lmdb_database, WriteMethod,
+    create_sorter, merge_cbo_roaring_bitmaps, sorter_into_lmdb_database, MergeFn, WriteMethod,
 };
 use crate::{Index, Result};
 
@@ -20,6 +18,7 @@ pub struct WordPrefixPairProximityDocids<'t, 'u, 'i> {
     pub(crate) chunk_compression_level: Option<u32>,
     pub(crate) max_nb_chunks: Option<usize>,
     pub(crate) max_memory: Option<usize>,
+    threshold: u32,
 }
 
 impl<'t, 'u, 'i> WordPrefixPairProximityDocids<'t, 'u, 'i> {
@@ -34,16 +33,26 @@ impl<'t, 'u, 'i> WordPrefixPairProximityDocids<'t, 'u, 'i> {
             chunk_compression_level: None,
             max_nb_chunks: None,
             max_memory: None,
+            threshold: 100,
         }
     }
 
+    /// Set the number of words required to make a prefix be part of the words prefixes
+    /// database. If a word prefix is supposed to match more than this number of words in the
+    /// dictionnary, therefore this prefix is added to the words prefixes datastructures.
+    ///
+    /// Default value is 100. This value must be higher than 50 and will be clamped
+    /// to these bound otherwise.
+    pub fn threshold(&mut self, value: u32) -> &mut Self {
+        self.threshold = value.max(50);
+        self
+    }
+
     pub fn execute(self) -> Result<()> {
         debug!("Computing and writing the word prefix pair proximity docids into LMDB on disk...");
 
         self.index.word_prefix_pair_proximity_docids.clear(self.wtxn)?;
 
-        let prefix_fst = self.index.words_prefixes_fst(self.wtxn)?;
-
         // Here we create a sorter akin to the previous one.
         let mut word_prefix_pair_proximity_docids_sorter = create_sorter(
             merge_cbo_roaring_bitmaps,
@@ -53,22 +62,59 @@ impl<'t, 'u, 'i> WordPrefixPairProximityDocids<'t, 'u, 'i> {
             self.max_memory,
         );
 
-        // We insert all the word pairs corresponding to the word-prefix pairs
-        // where the prefixes appears in the prefix FST previously constructed.
-        let db = self.index.word_pair_proximity_docids.remap_data_type::<ByteSlice>();
-        for result in db.iter(self.wtxn)? {
-            let ((word1, word2, prox), data) = result?;
-            let automaton = Str::new(word2).starts_with();
-            let mut matching_prefixes = prefix_fst.search(automaton).into_stream();
-            while let Some(prefix) = matching_prefixes.next() {
-                let prefix = str::from_utf8(prefix)?;
-                let pair = (word1, prefix, prox);
-                let bytes = StrStrU8Codec::bytes_encode(&pair).unwrap();
-                word_prefix_pair_proximity_docids_sorter.insert(bytes, data)?;
+        let prefix_fst = self.index.words_prefixes_fst(self.wtxn)?;
+        let prefix_fst_keys = prefix_fst.into_stream().into_bytes();
+        let prefix_fst_keys: Vec<_> = prefix_fst_keys
+            .as_slice()
+            .linear_group_by_key(|x| std::str::from_utf8(&x).unwrap().chars().nth(0).unwrap())
+            .collect();
+
+        let mut db =
+            self.index.word_pair_proximity_docids.remap_data_type::<ByteSlice>().iter(self.wtxn)?;
+
+        let mut buffer = Vec::new();
+        let mut current_prefixes: Option<&&[Vec<u8>]> = None;
+        let mut prefixes_cache = HashMap::new();
+        while let Some(((w1, w2, prox), data)) = db.next().transpose()? {
+            current_prefixes = match current_prefixes.take() {
+                Some(prefixes) if w2.as_bytes().starts_with(&prefixes[0]) => Some(prefixes),
+                _otherwise => {
+                    write_prefixes_in_sorter(
+                        &mut prefixes_cache,
+                        &mut word_prefix_pair_proximity_docids_sorter,
+                        self.threshold,
+                    )?;
+                    prefix_fst_keys.iter().find(|prefixes| w2.as_bytes().starts_with(&prefixes[0]))
+                }
+            };
+
+            if let Some(prefixes) = current_prefixes {
+                buffer.clear();
+                buffer.extend_from_slice(w1.as_bytes());
+                buffer.push(0);
+                for prefix in prefixes.iter().filter(|prefix| w2.as_bytes().starts_with(prefix)) {
+                    buffer.truncate(w1.len() + 1);
+                    buffer.extend_from_slice(prefix);
+                    buffer.push(prox);
+
+                    match prefixes_cache.get_mut(&buffer) {
+                        Some(value) => value.push(data),
+                        None => {
+                            prefixes_cache.insert(buffer.clone(), vec![data]);
+                        }
+                    }
+                }
             }
         }
 
+        write_prefixes_in_sorter(
+            &mut prefixes_cache,
+            &mut word_prefix_pair_proximity_docids_sorter,
+            self.threshold,
+        )?;
+
         drop(prefix_fst);
+        drop(db);
 
         // We finally write the word prefix pair proximity docids into the LMDB database.
         sorter_into_lmdb_database(
@@ -82,3 +128,25 @@ impl<'t, 'u, 'i> WordPrefixPairProximityDocids<'t, 'u, 'i> {
         Ok(())
     }
 }
+
+fn write_prefixes_in_sorter(
+    prefixes: &mut HashMap<Vec<u8>, Vec<&[u8]>>,
+    sorter: &mut grenad::Sorter<MergeFn>,
+    min_word_per_prefix: u32,
+) -> Result<()> {
+    for (i, (key, data_slices)) in prefixes.drain().enumerate() {
+        // if the number of words prefixed by the prefix is higher than the threshold,
+        // we insert it in the sorter.
+        if data_slices.len() > min_word_per_prefix as usize {
+            for data in data_slices {
+                sorter.insert(&key, data)?;
+            }
+        // if the first prefix isn't elligible for insertion,
+        // then the other prefixes can't be elligible.
+        } else if i == 0 {
+            break;
+        }
+    }
+
+    Ok(())
+}

milli/src/update/words_prefixes_fst.rs

@@ -8,7 +8,7 @@ use crate::{Index, Result, SmallString32};
 pub struct WordsPrefixesFst<'t, 'u, 'i> {
     wtxn: &'t mut heed::RwTxn<'i, 'u>,
     index: &'i Index,
-    threshold: f64,
+    threshold: u32,
     max_prefix_length: usize,
     _update_id: u64,
 }
@@ -22,20 +22,20 @@ impl<'t, 'u, 'i> WordsPrefixesFst<'t, 'u, 'i> {
         WordsPrefixesFst {
             wtxn,
             index,
-            threshold: 0.1 / 100.0, // .01%
+            threshold: 100,
             max_prefix_length: 4,
             _update_id: update_id,
         }
     }
 
-    /// Set the ratio of concerned words required to make a prefix be part of the words prefixes
+    /// Set the number of words required to make a prefix be part of the words prefixes
     /// database. If a word prefix is supposed to match more than this number of words in the
     /// dictionnary, therefore this prefix is added to the words prefixes datastructures.
     ///
-    /// Default value is `0.01` or `1%`. This value must be between 0 and 1 and will be clamped
-    /// to these bounds otherwise.
-    pub fn threshold(&mut self, value: f64) -> &mut Self {
-        self.threshold = value.min(1.0).max(0.0); // clamp [0, 1]
+    /// Default value is 100. This value must be higher than 50 and will be clamped
+    /// to this bound otherwise.
+    pub fn threshold(&mut self, value: u32) -> &mut Self {
+        self.threshold = value.max(50);
         self
     }
 
@@ -50,8 +50,6 @@ impl<'t, 'u, 'i> WordsPrefixesFst<'t, 'u, 'i> {
 
     pub fn execute(self) -> Result<()> {
         let words_fst = self.index.words_fst(&self.wtxn)?;
-        let number_of_words = words_fst.len();
-        let min_number_of_words = (number_of_words as f64 * self.threshold) as usize;
 
         let mut prefix_fsts = Vec::with_capacity(self.max_prefix_length);
         for n in 1..=self.max_prefix_length {
@@ -80,7 +78,7 @@ impl<'t, 'u, 'i> WordsPrefixesFst<'t, 'u, 'i> {
                 current_prefix_count += 1;
 
                 // There is enough words corresponding to this prefix to add it to the cache.
-                if current_prefix_count == min_number_of_words {
+                if current_prefix_count >= self.threshold {
                     builder.insert(prefix)?;
                 }
             }