remove get_val in serialization

fastfield_codecs/src/lib.rs

@@ -312,7 +312,7 @@ mod tests {
 
     #[test]
     fn estimation_test_bad_interpolation_case_monotonically_increasing() {
-        let mut data: Vec<u64> = (200..=20000_u64).collect();
+        let mut data: Vec<u64> = (201..=20000_u64).collect();
         data.push(1_000_000);
         let data: VecColumn = data.as_slice().into();
 

fastfield_codecs/src/line.rs

@@ -68,29 +68,37 @@ impl Line {
     }
 
     // Same as train, but the intercept is only estimated from provided sample positions
-    pub fn estimate(ys: &dyn Column, sample_positions: &[u64]) -> Self {
+    pub fn estimate(sample_positions_and_values: &[(u64, u64)]) -> Self {
+        let first_val = sample_positions_and_values[0].1;
+        let last_val = sample_positions_and_values[sample_positions_and_values.len() - 1].1;
+        let num_vals = sample_positions_and_values[sample_positions_and_values.len() - 1].0 + 1;
         Self::train_from(
-            ys,
-            sample_positions
-                .iter()
-                .cloned()
-                .map(|pos| (pos, ys.get_val(pos))),
+            first_val,
+            last_val,
+            num_vals,
+            sample_positions_and_values.iter().cloned(),
         )
     }
 
     // Intercept is only computed from provided positions
-    fn train_from(ys: &dyn Column, positions_and_values: impl Iterator<Item = (u64, u64)>) -> Self {
-        let num_vals = if let Some(num_vals) = NonZeroU64::new(ys.num_vals() - 1) {
-            num_vals
+    fn train_from(
+        first_val: u64,
+        last_val: u64,
+        num_vals: u64,
+        positions_and_values: impl Iterator<Item = (u64, u64)>,
+    ) -> Self {
+        // TODO replace with let else
+        let idx_last_val = if let Some(idx_last_val) = NonZeroU64::new(num_vals - 1) {
+            idx_last_val
         } else {
             return Line::default();
         };
 
-        let y0 = ys.get_val(0);
-        let y1 = ys.get_val(num_vals.get());
+        let y0 = first_val;
+        let y1 = last_val;
 
         // We first independently pick our slope.
-        let slope = compute_slope(y0, y1, num_vals);
+        let slope = compute_slope(y0, y1, idx_last_val);
 
         // We picked our slope. Note that it does not have to be perfect.
         // Now we need to compute the best intercept.
@@ -138,8 +146,12 @@ impl Line {
     /// This function is only invariable by translation if all of the
     /// `ys` are packaged into half of the space. (See heuristic below)
     pub fn train(ys: &dyn Column) -> Self {
+        let first_val = ys.iter().next().unwrap();
+        let last_val = ys.iter().nth(ys.num_vals() as usize - 1).unwrap();
         Self::train_from(
-            ys,
+            first_val,
+            last_val,
+            ys.num_vals(),
             ys.iter().enumerate().map(|(pos, val)| (pos as u64, val)),
         )
     }

fastfield_codecs/src/linear.rs

@@ -126,18 +126,20 @@ impl FastFieldCodec for LinearCodec {
             return None; // disable compressor for this case
         }
 
-        // let's sample at 0%, 5%, 10% .. 95%, 100%
-        let num_vals = column.num_vals() as f32 / 100.0;
-        let sample_positions = (0..20)
-            .map(|pos| (num_vals * pos as f32 * 5.0) as u64)
-            .collect::<Vec<_>>();
+        let limit_num_vals = column.num_vals().min(100_000);
 
-        let line = Line::estimate(column, &sample_positions);
+        let num_samples = 100;
+        let step_size = (limit_num_vals / num_samples).max(1); // 20 samples
+        let mut sample_positions_and_values: Vec<_> = Vec::new();
+        for (pos, val) in column.iter().enumerate().step_by(step_size as usize) {
+            sample_positions_and_values.push((pos as u64, val));
+        }
+
+        let line = Line::estimate(&sample_positions_and_values);
 
-        let estimated_bit_width = sample_positions
+        let estimated_bit_width = sample_positions_and_values
             .into_iter()
-            .map(|pos| {
-                let actual_value = column.get_val(pos);
+            .map(|(pos, actual_value)| {
                 let interpolated_val = line.eval(pos as u64);
                 actual_value.wrapping_sub(interpolated_val)
             })
@@ -146,6 +148,7 @@ impl FastFieldCodec for LinearCodec {
             .max()
             .unwrap_or(0);
 
+        // Extrapolate to whole column
         let num_bits = (estimated_bit_width as u64 * column.num_vals() as u64) + 64;
         let num_bits_uncompressed = 64 * column.num_vals();
         Some(num_bits as f32 / num_bits_uncompressed as f32)

src/fastfield/multivalued/writer.rs

@@ -1,5 +1,4 @@
 use std::io;
-use std::sync::Mutex;
 
 use fastfield_codecs::{Column, MonotonicallyMappableToU64, VecColumn};
 use fnv::FnvHashMap;
@@ -204,112 +203,68 @@ impl MultiValuedFastFieldWriter {
 pub(crate) struct MultivalueStartIndex<'a, C: Column> {
     column: &'a C,
     doc_id_map: &'a DocIdMapping,
-    min_max_opt: Mutex<Option<(u64, u64)>>,
-    random_seeker: Mutex<MultivalueStartIndexRandomSeeker<'a, C>>,
-}
-
-struct MultivalueStartIndexRandomSeeker<'a, C: Column> {
-    seek_head: MultivalueStartIndexIter<'a, C>,
-    seek_next_id: u64,
-}
-impl<'a, C: Column> MultivalueStartIndexRandomSeeker<'a, C> {
-    fn new(column: &'a C, doc_id_map: &'a DocIdMapping) -> Self {
-        Self {
-            seek_head: MultivalueStartIndexIter {
-                column,
-                doc_id_map,
-                new_doc_id: 0,
-                offset: 0u64,
-            },
-            seek_next_id: 0u64,
-        }
-    }
+    min: u64,
+    max: u64,
 }
 
 impl<'a, C: Column> MultivalueStartIndex<'a, C> {
     pub fn new(column: &'a C, doc_id_map: &'a DocIdMapping) -> Self {
         assert_eq!(column.num_vals(), doc_id_map.num_old_doc_ids() as u64 + 1);
+        let (min, max) =
+            tantivy_bitpacker::minmax(iter_remapped_multivalue_index(doc_id_map, column))
+                .unwrap_or((0u64, 0u64));
         MultivalueStartIndex {
             column,
             doc_id_map,
-            min_max_opt: Mutex::default(),
-            random_seeker: Mutex::new(MultivalueStartIndexRandomSeeker::new(column, doc_id_map)),
-        }
-    }
-
-    fn minmax(&self) -> (u64, u64) {
-        if let Some((min, max)) = *self.min_max_opt.lock().unwrap() {
-            return (min, max);
+            min,
+            max,
         }
-        let (min, max) = tantivy_bitpacker::minmax(self.iter()).unwrap_or((0u64, 0u64));
-        *self.min_max_opt.lock().unwrap() = Some((min, max));
-        (min, max)
     }
 }
 impl<'a, C: Column> Column for MultivalueStartIndex<'a, C> {
-    fn get_val(&self, idx: u64) -> u64 {
-        let mut random_seeker_lock = self.random_seeker.lock().unwrap();
-        if random_seeker_lock.seek_next_id > idx {
-            *random_seeker_lock =
-                MultivalueStartIndexRandomSeeker::new(self.column, self.doc_id_map);
-        }
-        let to_skip = idx - random_seeker_lock.seek_next_id;
-        random_seeker_lock.seek_next_id = idx + 1;
-        random_seeker_lock.seek_head.nth(to_skip as usize).unwrap()
+    fn get_val(&self, _idx: u64) -> u64 {
+        unimplemented!()
     }
 
     fn min_value(&self) -> u64 {
-        self.minmax().0
+        self.min
     }
 
     fn max_value(&self) -> u64 {
-        self.minmax().1
+        self.max
     }
 
     fn num_vals(&self) -> u64 {
         (self.doc_id_map.num_new_doc_ids() + 1) as u64
     }
 
-    fn iter<'b>(&'b self) -> Box<dyn Iterator<Item = u64> + 'b> {
-        Box::new(MultivalueStartIndexIter::new(self.column, self.doc_id_map))
-    }
-}
-
-struct MultivalueStartIndexIter<'a, C: Column> {
-    pub column: &'a C,
-    pub doc_id_map: &'a DocIdMapping,
-    pub new_doc_id: usize,
-    pub offset: u64,
-}
-
-impl<'a, C: Column> MultivalueStartIndexIter<'a, C> {
-    fn new(column: &'a C, doc_id_map: &'a DocIdMapping) -> Self {
-        Self {
-            column,
-            doc_id_map,
-            new_doc_id: 0,
-            offset: 0,
-        }
+    fn iter(&self) -> Box<dyn Iterator<Item = u64> + '_> {
+        Box::new(iter_remapped_multivalue_index(
+            self.doc_id_map,
+            &self.column,
+        ))
     }
 }
 
-impl<'a, C: Column> Iterator for MultivalueStartIndexIter<'a, C> {
-    type Item = u64;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        if self.new_doc_id > self.doc_id_map.num_new_doc_ids() {
-            return None;
-        }
-        let new_doc_id = self.new_doc_id;
-        self.new_doc_id += 1;
-        let start_offset = self.offset;
-        if new_doc_id < self.doc_id_map.num_new_doc_ids() {
-            let old_doc = self.doc_id_map.get_old_doc_id(new_doc_id as u32) as u64;
-            let num_vals_for_doc = self.column.get_val(old_doc + 1) - self.column.get_val(old_doc);
-            self.offset += num_vals_for_doc;
-        }
-        Some(start_offset)
-    }
+fn iter_remapped_multivalue_index<'a, C: Column>(
+    doc_id_map: &'a DocIdMapping,
+    column: &'a C,
+) -> impl Iterator<Item = u64> + 'a {
+    let mut offset = 0;
+    doc_id_map
+        .iter_old_doc_ids()
+        .chain(std::iter::once(u32::MAX))
+        .map(move |old_doc| {
+            if old_doc == u32::MAX {
+                // sentinel value for last offset
+                return offset;
+            }
+            let num_vals_for_doc =
+                column.get_val(old_doc as u64 + 1) - column.get_val(old_doc as u64);
+            let start_offset = offset;
+            offset += num_vals_for_doc;
+            start_offset
+        })
 }
 
 #[cfg(test)]
@@ -344,11 +299,5 @@ mod tests {
             vec![0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]
         );
         assert_eq!(multivalue_start_index.num_vals(), 11);
-        assert_eq!(multivalue_start_index.get_val(3), 2);
-        assert_eq!(multivalue_start_index.get_val(5), 5);
-        assert_eq!(multivalue_start_index.get_val(8), 21);
-        assert_eq!(multivalue_start_index.get_val(4), 3);
-        assert_eq!(multivalue_start_index.get_val(0), 0);
-        assert_eq!(multivalue_start_index.get_val(10), 55);
     }
 }

src/fastfield/writer.rs

@@ -391,15 +391,8 @@ impl<'map, 'bitp> Column for WriterFastFieldAccessProvider<'map, 'bitp> {
     /// # Panics
     ///
     /// May panic if `doc` is greater than the index.
-    fn get_val(&self, doc: u64) -> u64 {
-        if let Some(doc_id_map) = self.doc_id_map {
-            self.vals
-                .get(doc_id_map.get_old_doc_id(doc as u32) as usize) // consider extra
-                                                                     // FastFieldReader wrapper for
-                                                                     // non doc_id_map
-        } else {
-            self.vals.get(doc as usize)
-        }
+    fn get_val(&self, _doc: u64) -> u64 {
+        unimplemented!()
     }
 
     fn iter(&self) -> Box<dyn Iterator<Item = u64> + '_> {

src/indexer/doc_id_mapping.rs

@@ -34,10 +34,6 @@ impl SegmentDocIdMapping {
         self.new_doc_id_to_old_doc_addr.len()
     }
 
-    pub(crate) fn get_old_doc_addr(&self, new_doc_id: DocId) -> DocAddress {
-        self.new_doc_id_to_old_doc_addr[new_doc_id as usize]
-    }
-
     /// This flags means the segments are simply stacked in the order of their ordinal.
     /// e.g. [(0, 1), .. (n, 1), (0, 2)..., (m, 2)]
     ///

src/indexer/merger.rs

@@ -14,8 +14,8 @@ use crate::fastfield::{
 };
 use crate::fieldnorm::{FieldNormReader, FieldNormReaders, FieldNormsSerializer, FieldNormsWriter};
 use crate::indexer::doc_id_mapping::{expect_field_id_for_sort_field, SegmentDocIdMapping};
-use crate::indexer::sorted_doc_id_column::SortedDocIdColumn;
-use crate::indexer::sorted_doc_id_multivalue_column::SortedDocIdMultiValueColumn;
+use crate::indexer::sorted_doc_id_column::RemappedDocIdColumn;
+use crate::indexer::sorted_doc_id_multivalue_column::RemappedDocIdMultiValueColumn;
 use crate::indexer::SegmentSerializer;
 use crate::postings::{InvertedIndexSerializer, Postings, SegmentPostings};
 use crate::schema::{Cardinality, Field, FieldType, Schema};
@@ -310,7 +310,7 @@ impl IndexMerger {
         fast_field_serializer: &mut CompositeFastFieldSerializer,
         doc_id_mapping: &SegmentDocIdMapping,
     ) -> crate::Result<()> {
-        let fast_field_accessor = SortedDocIdColumn::new(&self.readers, doc_id_mapping, field);
+        let fast_field_accessor = RemappedDocIdColumn::new(&self.readers, doc_id_mapping, field);
         fast_field_serializer.create_auto_detect_u64_fast_field(field, fast_field_accessor)?;
 
         Ok(())
@@ -428,14 +428,8 @@ impl IndexMerger {
         fast_field_serializer: &mut CompositeFastFieldSerializer,
         doc_id_mapping: &SegmentDocIdMapping,
         reader_and_field_accessors: &[(&SegmentReader, T)],
-    ) -> crate::Result<Vec<u64>> {
-        // We can now create our `idx` serializer, and in a second pass,
-        // can effectively push the different indexes.
-
-        // copying into a temp vec is not ideal, but the fast field codec api requires random
-        // access, which is used in the estimation. It's possible to 1. calculate random
-        // access on the fly or 2. change the codec api to make random access optional, but
-        // they both have also major drawbacks.
+    ) -> crate::Result<()> {
+        // TODO Use `Column` implementation instead
 
         let mut offsets = Vec::with_capacity(doc_id_mapping.len());
         let mut offset = 0;
@@ -449,15 +443,15 @@ impl IndexMerger {
         let fastfield_accessor = VecColumn::from(&offsets[..]);
 
         fast_field_serializer.create_auto_detect_u64_fast_field(field, fastfield_accessor)?;
-        Ok(offsets)
+        Ok(())
     }
     /// Returns the fastfield index (index for the data, not the data).
     fn write_multi_value_fast_field_idx(
         &self,
         field: Field,
         fast_field_serializer: &mut CompositeFastFieldSerializer,
         doc_id_mapping: &SegmentDocIdMapping,
-    ) -> crate::Result<Vec<u64>> {
+    ) -> crate::Result<()> {
         let reader_ordinal_and_field_accessors = self
             .readers
             .iter()
@@ -561,16 +555,16 @@ impl IndexMerger {
         fast_field_serializer: &mut CompositeFastFieldSerializer,
         doc_id_mapping: &SegmentDocIdMapping,
     ) -> crate::Result<()> {
-        // Multifastfield consists in 2 fastfields.
+        // Multifastfield consists of 2 fastfields.
         // The first serves as an index into the second one and is strictly increasing.
         // The second contains the actual values.
 
         // First we merge the idx fast field.
-        let offsets =
-            self.write_multi_value_fast_field_idx(field, fast_field_serializer, doc_id_mapping)?;
+
+        self.write_multi_value_fast_field_idx(field, fast_field_serializer, doc_id_mapping)?;
 
         let fastfield_accessor =
-            SortedDocIdMultiValueColumn::new(&self.readers, doc_id_mapping, &offsets, field);
+            RemappedDocIdMultiValueColumn::new(&self.readers, doc_id_mapping, field);
         fast_field_serializer.create_auto_detect_u64_fast_field_with_idx(
             field,
             fastfield_accessor,