postings writer enum

Removes the Write generics argument in PostingsSerializer.
This removes useless generic.
Prepares the path for codecs.
Removes one useless CountingWrite layer.
etc.

src/codec/mod.rs

@@ -0,0 +1,49 @@
+mod postings;
+mod standard;
+
+use std::borrow::Cow;
+
+use serde::{Deserialize, Serialize};
+pub use standard::StandardCodec;
+
+pub trait Codec: Clone + std::fmt::Debug + Send + Sync + 'static {
+    type PostingsCodec;
+
+    const NAME: &'static str;
+
+    fn from_json_props(json_value: &serde_json::Value) -> crate::Result<Self>;
+    fn to_json_props(&self) -> serde_json::Value;
+}
+
+#[derive(Serialize, Deserialize, Clone, Debug)]
+pub struct CodecConfiguration {
+    name: Cow<'static, str>,
+    #[serde(default, skip_serializing_if = "serde_json::Value::is_null")]
+    props: serde_json::Value,
+}
+
+impl CodecConfiguration {
+    pub fn from_codec<C: Codec>(codec: &C) -> Self {
+        CodecConfiguration {
+            name: Cow::Borrowed(C::NAME),
+            props: codec.to_json_props(),
+        }
+    }
+
+    pub fn to_codec<C: Codec>(&self) -> crate::Result<C> {
+        if self.name != C::NAME {
+            return Err(crate::TantivyError::InvalidArgument(format!(
+                "Codec name mismatch: expected {}, got {}",
+                C::NAME,
+                self.name
+            )));
+        }
+        C::from_json_props(&self.props)
+    }
+}
+
+impl Default for CodecConfiguration {
+    fn default() -> Self {
+        CodecConfiguration::from_codec(&StandardCodec)
+    }
+}

src/codec/postings/mod.rs

@@ -0,0 +1,23 @@
+use std::io;
+
+use crate::fieldnorm::FieldNormReader;
+use crate::schema::IndexRecordOption;
+use crate::{DocId, Score};
+
+pub trait PostingsCodec {
+    type PostingsSerializer: PostingsSerializer;
+}
+
+pub trait PostingsSerializer {
+    fn new(
+        avg_fieldnorm: Score,
+        mode: IndexRecordOption,
+        fieldnorm_reader: Option<FieldNormReader>,
+    ) -> Self;
+
+    fn new_term(&mut self, term_doc_freq: u32, record_term_freq: bool);
+
+    fn write_doc(&mut self, doc_id: DocId, term_freq: u32);
+
+    fn close_term(&mut self, doc_freq: u32, wrt: &mut impl io::Write) -> io::Result<()>;
+}

src/codec/standard/mod.rs

@@ -0,0 +1,29 @@
+use serde::{Deserialize, Serialize};
+
+use crate::codec::standard::postings::StandardPostingsCodec;
+use crate::codec::Codec;
+
+mod postings;
+
+#[derive(Debug, Default, Clone, Serialize, Deserialize)]
+pub struct StandardCodec;
+
+impl Codec for StandardCodec {
+    type PostingsCodec = StandardPostingsCodec;
+
+    const NAME: &'static str = "standard";
+
+    fn from_json_props(json_value: &serde_json::Value) -> crate::Result<Self> {
+        if !json_value.is_null() {
+            return Err(crate::TantivyError::InvalidArgument(format!(
+                "Codec property for the StandardCodec are unexpected. expected null, got {}",
+                json_value.as_str().unwrap_or("null")
+            )));
+        }
+        Ok(StandardCodec)
+    }
+
+    fn to_json_props(&self) -> serde_json::Value {
+        serde_json::Value::Null
+    }
+}

src/codec/standard/postings/block.rs

@@ -0,0 +1,50 @@
+use crate::postings::compression::COMPRESSION_BLOCK_SIZE;
+use crate::DocId;
+
+pub struct Block {
+    doc_ids: [DocId; COMPRESSION_BLOCK_SIZE],
+    term_freqs: [u32; COMPRESSION_BLOCK_SIZE],
+    len: usize,
+}
+
+impl Block {
+    pub fn new() -> Self {
+        Block {
+            doc_ids: [0u32; COMPRESSION_BLOCK_SIZE],
+            term_freqs: [0u32; COMPRESSION_BLOCK_SIZE],
+            len: 0,
+        }
+    }
+
+    pub fn doc_ids(&self) -> &[DocId] {
+        &self.doc_ids[..self.len]
+    }
+
+    pub fn term_freqs(&self) -> &[u32] {
+        &self.term_freqs[..self.len]
+    }
+
+    pub fn clear(&mut self) {
+        self.len = 0;
+    }
+
+    pub fn append_doc(&mut self, doc: DocId, term_freq: u32) {
+        let len = self.len;
+        self.doc_ids[len] = doc;
+        self.term_freqs[len] = term_freq;
+        self.len = len + 1;
+    }
+
+    pub fn is_full(&self) -> bool {
+        self.len == COMPRESSION_BLOCK_SIZE
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.len == 0
+    }
+
+    pub fn last_doc(&self) -> DocId {
+        assert_eq!(self.len, COMPRESSION_BLOCK_SIZE);
+        self.doc_ids[COMPRESSION_BLOCK_SIZE - 1]
+    }
+}

src/codec/standard/postings/mod.rs

@@ -0,0 +1,13 @@
+use crate::codec::postings::PostingsCodec;
+
+mod block;
+mod postings_serializer;
+mod skip;
+
+pub use postings_serializer::StandardPostingsSerializer;
+
+pub struct StandardPostingsCodec;
+
+impl PostingsCodec for StandardPostingsCodec {
+    type PostingsSerializer = StandardPostingsSerializer;
+}

src/codec/standard/postings/postings_serializer.rs

@@ -0,0 +1,187 @@
+use std::cmp::Ordering;
+use std::io::{self, Write as _};
+
+use common::{BinarySerializable as _, VInt};
+
+use crate::codec::postings::PostingsSerializer;
+use crate::codec::standard::postings::block::Block;
+use crate::codec::standard::postings::skip::SkipSerializer;
+use crate::fieldnorm::FieldNormReader;
+use crate::postings::compression::{BlockEncoder, VIntEncoder as _, COMPRESSION_BLOCK_SIZE};
+use crate::query::Bm25Weight;
+use crate::schema::IndexRecordOption;
+use crate::{DocId, Score};
+
+pub struct StandardPostingsSerializer {
+    last_doc_id_encoded: u32,
+
+    block_encoder: BlockEncoder,
+    block: Box<Block>,
+
+    postings_write: Vec<u8>,
+    skip_write: SkipSerializer,
+
+    mode: IndexRecordOption,
+    fieldnorm_reader: Option<FieldNormReader>,
+
+    bm25_weight: Option<Bm25Weight>,
+    avg_fieldnorm: Score, /* Average number of term in the field for that segment.
+                           * this value is used to compute the block wand information. */
+    term_has_freq: bool,
+}
+
+impl PostingsSerializer for StandardPostingsSerializer {
+    fn new(
+        avg_fieldnorm: Score,
+        mode: IndexRecordOption,
+        fieldnorm_reader: Option<FieldNormReader>,
+    ) -> StandardPostingsSerializer {
+        Self {
+            block_encoder: BlockEncoder::new(),
+            block: Box::new(Block::new()),
+
+            postings_write: Vec::new(),
+            skip_write: SkipSerializer::new(),
+
+            last_doc_id_encoded: 0u32,
+            mode,
+
+            fieldnorm_reader,
+            bm25_weight: None,
+            avg_fieldnorm,
+            term_has_freq: false,
+        }
+    }
+
+    fn new_term(&mut self, term_doc_freq: u32, record_term_freq: bool) {
+        self.bm25_weight = None;
+
+        self.term_has_freq = self.mode.has_freq() && record_term_freq;
+        if !self.term_has_freq {
+            return;
+        }
+
+        let num_docs_in_segment: u64 =
+            if let Some(fieldnorm_reader) = self.fieldnorm_reader.as_ref() {
+                fieldnorm_reader.num_docs() as u64
+            } else {
+                return;
+            };
+
+        if num_docs_in_segment == 0 {
+            return;
+        }
+
+        self.bm25_weight = Some(Bm25Weight::for_one_term_without_explain(
+            term_doc_freq as u64,
+            num_docs_in_segment,
+            self.avg_fieldnorm,
+        ));
+    }
+
+    fn write_doc(&mut self, doc_id: DocId, term_freq: u32) {
+        self.block.append_doc(doc_id, term_freq);
+        if self.block.is_full() {
+            self.write_block();
+        }
+    }
+
+    fn close_term(
+        &mut self,
+        doc_freq: u32,
+        output_write: &mut impl std::io::Write,
+    ) -> io::Result<()> {
+        if !self.block.is_empty() {
+            // we have doc ids waiting to be written
+            // this happens when the number of doc ids is
+            // not a perfect multiple of our block size.
+            //
+            // In that case, the remaining part is encoded
+            // using variable int encoding.
+            {
+                let block_encoded = self
+                    .block_encoder
+                    .compress_vint_sorted(self.block.doc_ids(), self.last_doc_id_encoded);
+                self.postings_write.write_all(block_encoded)?;
+            }
+            // ... Idem for term frequencies
+            if self.term_has_freq {
+                let block_encoded = self
+                    .block_encoder
+                    .compress_vint_unsorted(self.block.term_freqs());
+                self.postings_write.write_all(block_encoded)?;
+            }
+            self.block.clear();
+        }
+        if doc_freq >= COMPRESSION_BLOCK_SIZE as u32 {
+            let skip_data = self.skip_write.data();
+            VInt(skip_data.len() as u64).serialize(output_write)?;
+            output_write.write_all(skip_data)?;
+        }
+        output_write.write_all(&self.postings_write[..])?;
+        self.skip_write.clear();
+        self.postings_write.clear();
+        self.bm25_weight = None;
+        Ok(())
+    }
+}
+
+impl StandardPostingsSerializer {
+    fn write_block(&mut self) {
+        {
+            // encode the doc ids
+            let (num_bits, block_encoded): (u8, &[u8]) = self
+                .block_encoder
+                .compress_block_sorted(self.block.doc_ids(), self.last_doc_id_encoded);
+            self.last_doc_id_encoded = self.block.last_doc();
+            self.skip_write
+                .write_doc(self.last_doc_id_encoded, num_bits);
+            // last el block 0, offset block 1,
+            self.postings_write.extend(block_encoded);
+        }
+        if self.term_has_freq {
+            let (num_bits, block_encoded): (u8, &[u8]) = self
+                .block_encoder
+                .compress_block_unsorted(self.block.term_freqs(), true);
+            self.postings_write.extend(block_encoded);
+            self.skip_write.write_term_freq(num_bits);
+            if self.mode.has_positions() {
+                // We serialize the sum of term freqs within the skip information
+                // in order to navigate through positions.
+                let sum_freq = self.block.term_freqs().iter().cloned().sum();
+                self.skip_write.write_total_term_freq(sum_freq);
+            }
+            let mut blockwand_params = (0u8, 0u32);
+            if let Some(bm25_weight) = self.bm25_weight.as_ref() {
+                if let Some(fieldnorm_reader) = self.fieldnorm_reader.as_ref() {
+                    let docs = self.block.doc_ids().iter().cloned();
+                    let term_freqs = self.block.term_freqs().iter().cloned();
+                    let fieldnorms = docs.map(|doc| fieldnorm_reader.fieldnorm_id(doc));
+                    blockwand_params = fieldnorms
+                        .zip(term_freqs)
+                        .max_by(
+                            |(left_fieldnorm_id, left_term_freq),
+                             (right_fieldnorm_id, right_term_freq)| {
+                                let left_score =
+                                    bm25_weight.tf_factor(*left_fieldnorm_id, *left_term_freq);
+                                let right_score =
+                                    bm25_weight.tf_factor(*right_fieldnorm_id, *right_term_freq);
+                                left_score
+                                    .partial_cmp(&right_score)
+                                    .unwrap_or(Ordering::Equal)
+                            },
+                        )
+                        .unwrap();
+                }
+            }
+            let (fieldnorm_id, term_freq) = blockwand_params;
+            self.skip_write.write_blockwand_max(fieldnorm_id, term_freq);
+        }
+        self.block.clear();
+    }
+
+    fn clear(&mut self) {
+        self.block.clear();
+        self.last_doc_id_encoded = 0;
+    }
+}

src/codec/standard/postings/skip.rs

@@ -0,0 +1,448 @@
+use crate::directory::OwnedBytes;
+use crate::postings::compression::{compressed_block_size, COMPRESSION_BLOCK_SIZE};
+use crate::query::Bm25Weight;
+use crate::schema::IndexRecordOption;
+use crate::{DocId, Score, TERMINATED};
+
+// doc num bits uses the following encoding:
+// given 0b a b cdefgh
+//         |1|2|3|  4  |
+// - 1: unused
+// - 2: is delta-1 encoded. 0 if not, 1, if yes
+// - 3: unused
+// - 4: a 5 bit number in 0..32, the actual bitwidth. Bitpacking could in theory say this is 32
+//   (requiring a 6th bit), but the biggest doc_id we can want to encode is TERMINATED-1, which can
+//   be represented on 31b without delta encoding.
+fn encode_bitwidth(bitwidth: u8, delta_1: bool) -> u8 {
+    assert!(bitwidth < 32);
+    bitwidth | ((delta_1 as u8) << 6)
+}
+
+fn decode_bitwidth(raw_bitwidth: u8) -> (u8, bool) {
+    let delta_1 = ((raw_bitwidth >> 6) & 1) != 0;
+    let bitwidth = raw_bitwidth & 0x1f;
+    (bitwidth, delta_1)
+}
+
+#[inline]
+fn encode_block_wand_max_tf(max_tf: u32) -> u8 {
+    max_tf.min(u8::MAX as u32) as u8
+}
+
+#[inline]
+fn decode_block_wand_max_tf(max_tf_code: u8) -> u32 {
+    if max_tf_code == u8::MAX {
+        u32::MAX
+    } else {
+        max_tf_code as u32
+    }
+}
+
+#[inline]
+fn read_u32(data: &[u8]) -> u32 {
+    u32::from_le_bytes(data[..4].try_into().unwrap())
+}
+
+#[inline]
+fn write_u32(val: u32, buf: &mut Vec<u8>) {
+    buf.extend_from_slice(&val.to_le_bytes());
+}
+
+pub struct SkipSerializer {
+    buffer: Vec<u8>,
+}
+
+impl SkipSerializer {
+    pub fn new() -> SkipSerializer {
+        SkipSerializer { buffer: Vec::new() }
+    }
+
+    pub fn write_doc(&mut self, last_doc: DocId, doc_num_bits: u8) {
+        write_u32(last_doc, &mut self.buffer);
+        self.buffer.push(encode_bitwidth(doc_num_bits, true));
+    }
+
+    pub fn write_term_freq(&mut self, tf_num_bits: u8) {
+        self.buffer.push(tf_num_bits);
+    }
+
+    pub fn write_total_term_freq(&mut self, tf_sum: u32) {
+        write_u32(tf_sum, &mut self.buffer);
+    }
+
+    pub fn write_blockwand_max(&mut self, fieldnorm_id: u8, term_freq: u32) {
+        let block_wand_tf = encode_block_wand_max_tf(term_freq);
+        self.buffer
+            .extend_from_slice(&[fieldnorm_id, block_wand_tf]);
+    }
+
+    pub fn data(&self) -> &[u8] {
+        &self.buffer[..]
+    }
+
+    pub fn clear(&mut self) {
+        self.buffer.clear();
+    }
+}
+
+#[derive(Clone)]
+pub(crate) struct SkipReader {
+    last_doc_in_block: DocId,
+    pub(crate) last_doc_in_previous_block: DocId,
+    owned_read: OwnedBytes,
+    skip_info: IndexRecordOption,
+    byte_offset: usize,
+    remaining_docs: u32, // number of docs remaining, including the
+    // documents in the current block.
+    block_info: BlockInfo,
+
+    position_offset: u64,
+}
+
+#[derive(Clone, Eq, PartialEq, Copy, Debug)]
+pub(crate) enum BlockInfo {
+    BitPacked {
+        doc_num_bits: u8,
+        strict_delta_encoded: bool,
+        tf_num_bits: u8,
+        tf_sum: u32,
+        block_wand_fieldnorm_id: u8,
+        block_wand_term_freq: u32,
+    },
+    VInt {
+        num_docs: u32,
+    },
+}
+
+impl Default for BlockInfo {
+    fn default() -> Self {
+        BlockInfo::VInt { num_docs: 0u32 }
+    }
+}
+
+impl SkipReader {
+    pub fn new(data: OwnedBytes, doc_freq: u32, skip_info: IndexRecordOption) -> SkipReader {
+        let mut skip_reader = SkipReader {
+            last_doc_in_block: if doc_freq >= COMPRESSION_BLOCK_SIZE as u32 {
+                0
+            } else {
+                TERMINATED
+            },
+            last_doc_in_previous_block: 0u32,
+            owned_read: data,
+            skip_info,
+            block_info: BlockInfo::VInt { num_docs: doc_freq },
+            byte_offset: 0,
+            remaining_docs: doc_freq,
+            position_offset: 0u64,
+        };
+        if doc_freq >= COMPRESSION_BLOCK_SIZE as u32 {
+            skip_reader.read_block_info();
+        }
+        skip_reader
+    }
+
+    pub fn reset(&mut self, data: OwnedBytes, doc_freq: u32) {
+        self.last_doc_in_block = if doc_freq >= COMPRESSION_BLOCK_SIZE as u32 {
+            0
+        } else {
+            TERMINATED
+        };
+        self.last_doc_in_previous_block = 0u32;
+        self.owned_read = data;
+        self.block_info = BlockInfo::VInt { num_docs: doc_freq };
+        self.byte_offset = 0;
+        self.remaining_docs = doc_freq;
+        self.position_offset = 0u64;
+        if doc_freq >= COMPRESSION_BLOCK_SIZE as u32 {
+            self.read_block_info();
+        }
+    }
+
+    // Returns the block max score for this block if available.
+    //
+    // The block max score is available for all full bitpacked block,
+    // but no available for the last VInt encoded incomplete block.
+    pub fn block_max_score(&self, bm25_weight: &Bm25Weight) -> Option<Score> {
+        match self.block_info {
+            BlockInfo::BitPacked {
+                block_wand_fieldnorm_id,
+                block_wand_term_freq,
+                ..
+            } => Some(bm25_weight.score(block_wand_fieldnorm_id, block_wand_term_freq)),
+            BlockInfo::VInt { .. } => None,
+        }
+    }
+
+    pub(crate) fn last_doc_in_block(&self) -> DocId {
+        self.last_doc_in_block
+    }
+
+    pub fn position_offset(&self) -> u64 {
+        self.position_offset
+    }
+
+    #[inline]
+    pub fn byte_offset(&self) -> usize {
+        self.byte_offset
+    }
+
+    fn read_block_info(&mut self) {
+        let bytes = self.owned_read.as_slice();
+        let advance_len: usize;
+        self.last_doc_in_block = read_u32(bytes);
+        let (doc_num_bits, strict_delta_encoded) = decode_bitwidth(bytes[4]);
+        match self.skip_info {
+            IndexRecordOption::Basic => {
+                advance_len = 5;
+                self.block_info = BlockInfo::BitPacked {
+                    doc_num_bits,
+                    strict_delta_encoded,
+                    tf_num_bits: 0,
+                    tf_sum: 0,
+                    block_wand_fieldnorm_id: 0,
+                    block_wand_term_freq: 0,
+                };
+            }
+            IndexRecordOption::WithFreqs => {
+                let tf_num_bits = bytes[5];
+                let block_wand_fieldnorm_id = bytes[6];
+                let block_wand_term_freq = decode_block_wand_max_tf(bytes[7]);
+                advance_len = 8;
+                self.block_info = BlockInfo::BitPacked {
+                    doc_num_bits,
+                    strict_delta_encoded,
+                    tf_num_bits,
+                    tf_sum: 0,
+                    block_wand_fieldnorm_id,
+                    block_wand_term_freq,
+                };
+            }
+            IndexRecordOption::WithFreqsAndPositions => {
+                let tf_num_bits = bytes[5];
+                let tf_sum = read_u32(&bytes[6..10]);
+                let block_wand_fieldnorm_id = bytes[10];
+                let block_wand_term_freq = decode_block_wand_max_tf(bytes[11]);
+                advance_len = 12;
+                self.block_info = BlockInfo::BitPacked {
+                    doc_num_bits,
+                    strict_delta_encoded,
+                    tf_num_bits,
+                    tf_sum,
+                    block_wand_fieldnorm_id,
+                    block_wand_term_freq,
+                };
+            }
+        }
+        self.owned_read.advance(advance_len);
+    }
+
+    pub fn block_info(&self) -> BlockInfo {
+        self.block_info
+    }
+
+    /// Advance the skip reader to the block that may contain the target.
+    ///
+    /// If the target is larger than all documents, the skip_reader
+    /// then advance to the last Variable In block.
+    pub fn seek(&mut self, target: DocId) -> bool {
+        if self.last_doc_in_block() >= target {
+            return false;
+        }
+        loop {
+            self.advance();
+            if self.last_doc_in_block() >= target {
+                return true;
+            }
+        }
+    }
+
+    pub fn advance(&mut self) {
+        match self.block_info {
+            BlockInfo::BitPacked {
+                doc_num_bits,
+                tf_num_bits,
+                tf_sum,
+                ..
+            } => {
+                self.remaining_docs -= COMPRESSION_BLOCK_SIZE as u32;
+                self.byte_offset += compressed_block_size(doc_num_bits + tf_num_bits);
+                self.position_offset += tf_sum as u64;
+            }
+            BlockInfo::VInt { num_docs } => {
+                debug_assert_eq!(num_docs, self.remaining_docs);
+                self.remaining_docs = 0;
+                self.byte_offset = usize::MAX;
+            }
+        }
+        self.last_doc_in_previous_block = self.last_doc_in_block;
+        if self.remaining_docs >= COMPRESSION_BLOCK_SIZE as u32 {
+            self.read_block_info();
+        } else {
+            self.last_doc_in_block = TERMINATED;
+            self.block_info = BlockInfo::VInt {
+                num_docs: self.remaining_docs,
+            };
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+
+    use super::{
+        decode_bitwidth, encode_bitwidth, BlockInfo, IndexRecordOption, SkipReader, SkipSerializer,
+    };
+    use crate::directory::OwnedBytes;
+    use crate::postings::compression::COMPRESSION_BLOCK_SIZE;
+
+    #[test]
+    fn test_encode_block_wand_max_tf() {
+        for tf in 0..255 {
+            assert_eq!(super::encode_block_wand_max_tf(tf), tf as u8);
+        }
+        for &tf in &[255, 256, 1_000_000, u32::MAX] {
+            assert_eq!(super::encode_block_wand_max_tf(tf), 255);
+        }
+    }
+
+    #[test]
+    fn test_decode_block_wand_max_tf() {
+        for tf in 0..255 {
+            assert_eq!(super::decode_block_wand_max_tf(tf), tf as u32);
+        }
+        assert_eq!(super::decode_block_wand_max_tf(255), u32::MAX);
+    }
+
+    #[test]
+    fn test_skip_with_freq() {
+        let buf = {
+            let mut skip_serializer = SkipSerializer::new();
+            skip_serializer.write_doc(1u32, 2u8);
+            skip_serializer.write_term_freq(3u8);
+            skip_serializer.write_blockwand_max(13u8, 3u32);
+            skip_serializer.write_doc(5u32, 5u8);
+            skip_serializer.write_term_freq(2u8);
+            skip_serializer.write_blockwand_max(8u8, 2u32);
+            skip_serializer.data().to_owned()
+        };
+        let doc_freq = 3u32 + (COMPRESSION_BLOCK_SIZE * 2) as u32;
+        let mut skip_reader =
+            SkipReader::new(OwnedBytes::new(buf), doc_freq, IndexRecordOption::WithFreqs);
+        assert_eq!(skip_reader.last_doc_in_block(), 1u32);
+        assert_eq!(
+            skip_reader.block_info,
+            BlockInfo::BitPacked {
+                doc_num_bits: 2u8,
+                strict_delta_encoded: true,
+                tf_num_bits: 3u8,
+                tf_sum: 0,
+                block_wand_fieldnorm_id: 13,
+                block_wand_term_freq: 3
+            }
+        );
+        skip_reader.advance();
+        assert_eq!(skip_reader.last_doc_in_block(), 5u32);
+        assert_eq!(
+            skip_reader.block_info(),
+            BlockInfo::BitPacked {
+                doc_num_bits: 5u8,
+                strict_delta_encoded: true,
+                tf_num_bits: 2u8,
+                tf_sum: 0,
+                block_wand_fieldnorm_id: 8,
+                block_wand_term_freq: 2
+            }
+        );
+        skip_reader.advance();
+        assert_eq!(skip_reader.block_info(), BlockInfo::VInt { num_docs: 3u32 });
+        skip_reader.advance();
+        assert_eq!(skip_reader.block_info(), BlockInfo::VInt { num_docs: 0u32 });
+        skip_reader.advance();
+        assert_eq!(skip_reader.block_info(), BlockInfo::VInt { num_docs: 0u32 });
+    }
+
+    #[test]
+    fn test_skip_no_freq() {
+        let buf = {
+            let mut skip_serializer = SkipSerializer::new();
+            skip_serializer.write_doc(1u32, 2u8);
+            skip_serializer.write_doc(5u32, 5u8);
+            skip_serializer.data().to_owned()
+        };
+        let doc_freq = 3u32 + (COMPRESSION_BLOCK_SIZE * 2) as u32;
+        let mut skip_reader =
+            SkipReader::new(OwnedBytes::new(buf), doc_freq, IndexRecordOption::Basic);
+        assert_eq!(skip_reader.last_doc_in_block(), 1u32);
+        assert_eq!(
+            skip_reader.block_info(),
+            BlockInfo::BitPacked {
+                doc_num_bits: 2u8,
+                strict_delta_encoded: true,
+                tf_num_bits: 0,
+                tf_sum: 0u32,
+                block_wand_fieldnorm_id: 0,
+                block_wand_term_freq: 0
+            }
+        );
+        skip_reader.advance();
+        assert_eq!(skip_reader.last_doc_in_block(), 5u32);
+        assert_eq!(
+            skip_reader.block_info(),
+            BlockInfo::BitPacked {
+                doc_num_bits: 5u8,
+                strict_delta_encoded: true,
+                tf_num_bits: 0,
+                tf_sum: 0u32,
+                block_wand_fieldnorm_id: 0,
+                block_wand_term_freq: 0
+            }
+        );
+        skip_reader.advance();
+        assert_eq!(skip_reader.block_info(), BlockInfo::VInt { num_docs: 3u32 });
+        skip_reader.advance();
+        assert_eq!(skip_reader.block_info(), BlockInfo::VInt { num_docs: 0u32 });
+        skip_reader.advance();
+        assert_eq!(skip_reader.block_info(), BlockInfo::VInt { num_docs: 0u32 });
+    }
+
+    #[test]
+    fn test_skip_multiple_of_block_size() {
+        let buf = {
+            let mut skip_serializer = SkipSerializer::new();
+            skip_serializer.write_doc(1u32, 2u8);
+            skip_serializer.data().to_owned()
+        };
+        let doc_freq = COMPRESSION_BLOCK_SIZE as u32;
+        let mut skip_reader =
+            SkipReader::new(OwnedBytes::new(buf), doc_freq, IndexRecordOption::Basic);
+        assert_eq!(skip_reader.last_doc_in_block(), 1u32);
+        assert_eq!(
+            skip_reader.block_info(),
+            BlockInfo::BitPacked {
+                doc_num_bits: 2u8,
+                strict_delta_encoded: true,
+                tf_num_bits: 0,
+                tf_sum: 0u32,
+                block_wand_fieldnorm_id: 0,
+                block_wand_term_freq: 0
+            }
+        );
+        skip_reader.advance();
+        assert_eq!(skip_reader.block_info(), BlockInfo::VInt { num_docs: 0u32 });
+    }
+
+    #[test]
+    fn test_encode_decode_bitwidth() {
+        for bitwidth in 0..32 {
+            for delta_1 in [false, true] {
+                assert_eq!(
+                    (bitwidth, delta_1),
+                    decode_bitwidth(encode_bitwidth(bitwidth, delta_1))
+                );
+            }
+        }
+        assert_eq!(0b01000010, encode_bitwidth(0b10, true));
+        assert_eq!(0b00000010, encode_bitwidth(0b10, false));
+    }
+}

src/index/index.rs

@@ -8,6 +8,7 @@ use std::thread::available_parallelism;
 use super::segment::Segment;
 use super::segment_reader::merge_field_meta_data;
 use super::{FieldMetadata, IndexSettings};
+use crate::codec::{CodecConfiguration, StandardCodec};
 use crate::core::{Executor, META_FILEPATH};
 use crate::directory::error::OpenReadError;
 #[cfg(feature = "mmap")]
@@ -59,6 +60,7 @@ fn save_new_metas(
     schema: Schema,
     index_settings: IndexSettings,
     directory: &dyn Directory,
+    codec: CodecConfiguration,
 ) -> crate::Result<()> {
     save_metas(
         &IndexMeta {
@@ -67,6 +69,7 @@ fn save_new_metas(
             schema,
             opstamp: 0u64,
             payload: None,
+            codec,
         },
         directory,
     )?;
@@ -101,18 +104,21 @@ fn save_new_metas(
 /// };
 /// let index = Index::builder().schema(schema).settings(settings).create_in_ram();
 /// ```
-pub struct IndexBuilder {
+pub struct IndexBuilder<Codec: crate::codec::Codec = StandardCodec> {
     schema: Option<Schema>,
     index_settings: IndexSettings,
     tokenizer_manager: TokenizerManager,
     fast_field_tokenizer_manager: TokenizerManager,
+    codec: Codec,
 }
-impl Default for IndexBuilder {
+
+impl Default for IndexBuilder<StandardCodec> {
     fn default() -> Self {
         IndexBuilder::new()
     }
 }
-impl IndexBuilder {
+
+impl IndexBuilder<StandardCodec> {
     /// Creates a new `IndexBuilder`
     pub fn new() -> Self {
         Self {
@@ -120,6 +126,21 @@ impl IndexBuilder {
             index_settings: IndexSettings::default(),
             tokenizer_manager: TokenizerManager::default(),
             fast_field_tokenizer_manager: TokenizerManager::default(),
+            codec: StandardCodec,
+        }
+    }
+}
+
+impl<Codec: crate::codec::Codec> IndexBuilder<Codec> {
+    /// Set the codec
+    #[must_use]
+    pub fn codec<NewCodec: crate::codec::Codec>(self, codec: NewCodec) -> IndexBuilder<NewCodec> {
+        IndexBuilder {
+            schema: self.schema,
+            index_settings: self.index_settings,
+            tokenizer_manager: self.tokenizer_manager,
+            fast_field_tokenizer_manager: self.fast_field_tokenizer_manager,
+            codec,
         }
     }
 
@@ -154,7 +175,7 @@ impl IndexBuilder {
     /// The index will be allocated in anonymous memory.
     /// This is useful for indexing small set of documents
     /// for instances like unit test or temporary in memory index.
-    pub fn create_in_ram(self) -> Result<Index, TantivyError> {
+    pub fn create_in_ram(self) -> Result<Index<Codec>, TantivyError> {
         let ram_directory = RamDirectory::create();
         self.create(ram_directory)
     }
@@ -165,7 +186,7 @@ impl IndexBuilder {
     /// If a previous index was in this directory, it returns an
     /// [`TantivyError::IndexAlreadyExists`] error.
     #[cfg(feature = "mmap")]
-    pub fn create_in_dir<P: AsRef<Path>>(self, directory_path: P) -> crate::Result<Index> {
+    pub fn create_in_dir<P: AsRef<Path>>(self, directory_path: P) -> crate::Result<Index<Codec>> {
         let mmap_directory: Box<dyn Directory> = Box::new(MmapDirectory::open(directory_path)?);
         if Index::exists(&*mmap_directory)? {
             return Err(TantivyError::IndexAlreadyExists);
@@ -186,7 +207,7 @@ impl IndexBuilder {
         self,
         dir: impl Into<Box<dyn Directory>>,
         mem_budget: usize,
-    ) -> crate::Result<SingleSegmentIndexWriter<D>> {
+    ) -> crate::Result<SingleSegmentIndexWriter<Codec, D>> {
         let index = self.create(dir)?;
         let index_simple_writer = SingleSegmentIndexWriter::new(index, mem_budget)?;
         Ok(index_simple_writer)
@@ -202,7 +223,7 @@ impl IndexBuilder {
     /// For other unit tests, prefer the [`RamDirectory`], see:
     /// [`IndexBuilder::create_in_ram()`].
     #[cfg(feature = "mmap")]
-    pub fn create_from_tempdir(self) -> crate::Result<Index> {
+    pub fn create_from_tempdir(self) -> crate::Result<Index<Codec>> {
         let mmap_directory: Box<dyn Directory> = Box::new(MmapDirectory::create_from_tempdir()?);
         self.create(mmap_directory)
     }
@@ -215,12 +236,15 @@ impl IndexBuilder {
     }
 
     /// Opens or creates a new index in the provided directory
-    pub fn open_or_create<T: Into<Box<dyn Directory>>>(self, dir: T) -> crate::Result<Index> {
+    pub fn open_or_create<T: Into<Box<dyn Directory>>>(
+        self,
+        dir: T,
+    ) -> crate::Result<Index<Codec>> {
         let dir: Box<dyn Directory> = dir.into();
         if !Index::exists(&*dir)? {
             return self.create(dir);
         }
-        let mut index = Index::open(dir)?;
+        let mut index: Index<Codec> = Index::<Codec>::open_with_codec(dir)?;
         index.set_tokenizers(self.tokenizer_manager.clone());
         if index.schema() == self.get_expect_schema()? {
             Ok(index)
@@ -244,18 +268,26 @@ impl IndexBuilder {
     /// Creates a new index given an implementation of the trait `Directory`.
     ///
     /// If a directory previously existed, it will be erased.
-    fn create<T: Into<Box<dyn Directory>>>(self, dir: T) -> crate::Result<Index> {
+    pub fn create<T: Into<Box<dyn Directory>>>(self, dir: T) -> crate::Result<Index<Codec>> {
+        self.create_avoid_monomorphization(dir.into())
+    }
+
+    fn create_avoid_monomorphization(self, dir: Box<dyn Directory>) -> crate::Result<Index<Codec>> {
         self.validate()?;
         let dir = dir.into();
         let directory = ManagedDirectory::wrap(dir)?;
+        let codec: CodecConfiguration = CodecConfiguration::from_codec(&self.codec);
         save_new_metas(
             self.get_expect_schema()?,
             self.index_settings.clone(),
             &directory,
+            codec,
         )?;
-        let mut metas = IndexMeta::with_schema(self.get_expect_schema()?);
+        let schema = self.get_expect_schema()?;
+        let mut metas = IndexMeta::with_schema_and_codec(schema, &self.codec);
         metas.index_settings = self.index_settings;
-        let mut index = Index::open_from_metas(directory, &metas, SegmentMetaInventory::default());
+        let mut index: Index<Codec> =
+            Index::<Codec>::open_from_metas(directory, &metas, SegmentMetaInventory::default())?;
         index.set_tokenizers(self.tokenizer_manager);
         index.set_fast_field_tokenizers(self.fast_field_tokenizer_manager);
         Ok(index)
@@ -264,7 +296,7 @@ impl IndexBuilder {
 
 /// Search Index
 #[derive(Clone)]
-pub struct Index {
+pub struct Index<Codec: crate::codec::Codec = crate::codec::StandardCodec> {
     directory: ManagedDirectory,
     schema: Schema,
     settings: IndexSettings,
@@ -272,6 +304,7 @@ pub struct Index {
     tokenizers: TokenizerManager,
     fast_field_tokenizers: TokenizerManager,
     inventory: SegmentMetaInventory,
+    codec: Codec,
 }
 
 impl Index {
@@ -279,41 +312,6 @@ impl Index {
     pub fn builder() -> IndexBuilder {
         IndexBuilder::new()
     }
-    /// Examines the directory to see if it contains an index.
-    ///
-    /// Effectively, it only checks for the presence of the `meta.json` file.
-    pub fn exists(dir: &dyn Directory) -> Result<bool, OpenReadError> {
-        dir.exists(&META_FILEPATH)
-    }
-
-    /// Accessor to the search executor.
-    ///
-    /// This pool is used by default when calling `searcher.search(...)`
-    /// to perform search on the individual segments.
-    ///
-    /// By default the executor is single thread, and simply runs in the calling thread.
-    pub fn search_executor(&self) -> &Executor {
-        &self.executor
-    }
-
-    /// Replace the default single thread search executor pool
-    /// by a thread pool with a given number of threads.
-    pub fn set_multithread_executor(&mut self, num_threads: usize) -> crate::Result<()> {
-        self.executor = Executor::multi_thread(num_threads, "tantivy-search-")?;
-        Ok(())
-    }
-
-    /// Custom thread pool by a outer thread pool.
-    pub fn set_executor(&mut self, executor: Executor) {
-        self.executor = executor;
-    }
-
-    /// Replace the default single thread search executor pool
-    /// by a thread pool with as many threads as there are CPUs on the system.
-    pub fn set_default_multithread_executor(&mut self) -> crate::Result<()> {
-        let default_num_threads = available_parallelism()?.get();
-        self.set_multithread_executor(default_num_threads)
-    }
 
     /// Creates a new index using the [`RamDirectory`].
     ///
@@ -324,6 +322,13 @@ impl Index {
         IndexBuilder::new().schema(schema).create_in_ram().unwrap()
     }
 
+    /// Examines the directory to see if it contains an index.
+    ///
+    /// Effectively, it only checks for the presence of the `meta.json` file.
+    pub fn exists(directory: &dyn Directory) -> Result<bool, OpenReadError> {
+        directory.exists(&META_FILEPATH)
+    }
+
     /// Creates a new index in a given filepath.
     /// The index will use the [`MmapDirectory`].
     ///
@@ -370,20 +375,107 @@ impl Index {
         schema: Schema,
         settings: IndexSettings,
     ) -> crate::Result<Index> {
-        let dir: Box<dyn Directory> = dir.into();
+        Self::create_to_avoid_monomorphization(dir.into(), schema, settings)
+    }
+
+    fn create_to_avoid_monomorphization(
+        dir: Box<dyn Directory>,
+        schema: Schema,
+        settings: IndexSettings,
+    ) -> crate::Result<Index> {
         let mut builder = IndexBuilder::new().schema(schema);
         builder = builder.settings(settings);
         builder.create(dir)
     }
 
+    /// Opens a new directory from an index path.
+    #[cfg(feature = "mmap")]
+    pub fn open_in_dir<P: AsRef<Path>>(directory_path: P) -> crate::Result<Index> {
+        Self::open_in_dir_to_avoid_monomorphization(directory_path.as_ref())
+    }
+
+    #[inline(never)]
+    fn open_in_dir_to_avoid_monomorphization(directory_path: &Path) -> crate::Result<Index> {
+        let mmap_directory = MmapDirectory::open(directory_path)?;
+        Index::open(mmap_directory)
+    }
+
+    /// Open the index using the provided directory
+    pub fn open<T: Into<Box<dyn Directory>>>(directory: T) -> crate::Result<Index> {
+        Index::<StandardCodec>::open_with_codec(directory.into())
+    }
+}
+
+impl<Codec: crate::codec::Codec> Index<Codec> {
+    /// Returns a version of this index with the standard codec.
+    /// This is useful when you need to pass the index to APIs that
+    /// don't care about the codec (e.g., for reading).
+    pub(crate) fn with_standard_codec(&self) -> Index<StandardCodec> {
+        Index {
+            directory: self.directory.clone(),
+            schema: self.schema.clone(),
+            settings: self.settings.clone(),
+            executor: self.executor.clone(),
+            tokenizers: self.tokenizers.clone(),
+            fast_field_tokenizers: self.fast_field_tokenizers.clone(),
+            inventory: self.inventory.clone(),
+            codec: StandardCodec::default(),
+        }
+    }
+
+    /// Open the index using the provided directory
+    #[inline(never)]
+    pub fn open_with_codec(directory: Box<dyn Directory>) -> crate::Result<Index<Codec>> {
+        let directory = ManagedDirectory::wrap(directory)?;
+        let inventory = SegmentMetaInventory::default();
+        let metas = load_metas(&directory, &inventory)?;
+        let index: Index<Codec> = Index::<Codec>::open_from_metas(directory, &metas, inventory)?;
+        Ok(index)
+    }
+
+    /// Accessor to the codec.
+    pub fn codec(&self) -> &Codec {
+        &self.codec
+    }
+
+    /// Accessor to the search executor.
+    ///
+    /// This pool is used by default when calling `searcher.search(...)`
+    /// to perform search on the individual segments.
+    ///
+    /// By default the executor is single thread, and simply runs in the calling thread.
+    pub fn search_executor(&self) -> &Executor {
+        &self.executor
+    }
+
+    /// Replace the default single thread search executor pool
+    /// by a thread pool with a given number of threads.
+    pub fn set_multithread_executor(&mut self, num_threads: usize) -> crate::Result<()> {
+        self.executor = Executor::multi_thread(num_threads, "tantivy-search-")?;
+        Ok(())
+    }
+
+    /// Custom thread pool by a outer thread pool.
+    pub fn set_executor(&mut self, executor: Executor) {
+        self.executor = executor;
+    }
+
+    /// Replace the default single thread search executor pool
+    /// by a thread pool with as many threads as there are CPUs on the system.
+    pub fn set_default_multithread_executor(&mut self) -> crate::Result<()> {
+        let default_num_threads = available_parallelism()?.get();
+        self.set_multithread_executor(default_num_threads)
+    }
+
     /// Creates a new index given a directory and an [`IndexMeta`].
-    fn open_from_metas(
+    fn open_from_metas<C: crate::codec::Codec>(
         directory: ManagedDirectory,
         metas: &IndexMeta,
         inventory: SegmentMetaInventory,
-    ) -> Index {
+    ) -> crate::Result<Index<C>> {
         let schema = metas.schema.clone();
-        Index {
+        let codec = metas.codec.to_codec::<C>()?;
+        Ok(Index {
             settings: metas.index_settings.clone(),
             directory,
             schema,
@@ -391,7 +483,8 @@ impl Index {
             fast_field_tokenizers: TokenizerManager::default(),
             executor: Executor::single_thread(),
             inventory,
-        }
+            codec,
+        })
     }
 
     /// Setter for the tokenizer manager.
@@ -447,7 +540,7 @@ impl Index {
     /// Create a default [`IndexReader`] for the given index.
     ///
     /// See [`Index.reader_builder()`].
-    pub fn reader(&self) -> crate::Result<IndexReader> {
+    pub fn reader(&self) -> crate::Result<IndexReader<Codec>> {
         self.reader_builder().try_into()
     }
 
@@ -455,17 +548,10 @@ impl Index {
     ///
     /// Most project should create at most one reader for a given index.
     /// This method is typically called only once per `Index` instance.
-    pub fn reader_builder(&self) -> IndexReaderBuilder {
+    pub fn reader_builder(&self) -> IndexReaderBuilder<Codec> {
         IndexReaderBuilder::new(self.clone())
     }
 
-    /// Opens a new directory from an index path.
-    #[cfg(feature = "mmap")]
-    pub fn open_in_dir<P: AsRef<Path>>(directory_path: P) -> crate::Result<Index> {
-        let mmap_directory = MmapDirectory::open(directory_path)?;
-        Index::open(mmap_directory)
-    }
-
     /// Returns the list of the segment metas tracked by the index.
     ///
     /// Such segments can of course be part of the index,
@@ -506,16 +592,6 @@ impl Index {
         self.inventory.new_segment_meta(segment_id, max_doc)
     }
 
-    /// Open the index using the provided directory
-    pub fn open<T: Into<Box<dyn Directory>>>(directory: T) -> crate::Result<Index> {
-        let directory = directory.into();
-        let directory = ManagedDirectory::wrap(directory)?;
-        let inventory = SegmentMetaInventory::default();
-        let metas = load_metas(&directory, &inventory)?;
-        let index = Index::open_from_metas(directory, &metas, inventory);
-        Ok(index)
-    }
-
     /// Reads the index meta file from the directory.
     pub fn load_metas(&self) -> crate::Result<IndexMeta> {
         load_metas(self.directory(), &self.inventory)
@@ -539,7 +615,7 @@ impl Index {
     pub fn writer_with_options<D: Document>(
         &self,
         options: IndexWriterOptions,
-    ) -> crate::Result<IndexWriter<D>> {
+    ) -> crate::Result<IndexWriter<Codec, D>> {
         let directory_lock = self
             .directory
             .acquire_lock(&INDEX_WRITER_LOCK)
@@ -581,7 +657,7 @@ impl Index {
         &self,
         num_threads: usize,
         overall_memory_budget_in_bytes: usize,
-    ) -> crate::Result<IndexWriter<D>> {
+    ) -> crate::Result<IndexWriter<Codec, D>> {
         let memory_arena_in_bytes_per_thread = overall_memory_budget_in_bytes / num_threads;
         let options = IndexWriterOptions::builder()
             .num_worker_threads(num_threads)
@@ -595,7 +671,7 @@ impl Index {
     /// That index writer only simply has a single thread and a memory budget of 15 MB.
     /// Using a single thread gives us a deterministic allocation of DocId.
     #[cfg(test)]
-    pub fn writer_for_tests<D: Document>(&self) -> crate::Result<IndexWriter<D>> {
+    pub fn writer_for_tests<D: Document>(&self) -> crate::Result<IndexWriter<Codec, D>> {
         self.writer_with_num_threads(1, MEMORY_BUDGET_NUM_BYTES_MIN)
     }
 
@@ -613,7 +689,7 @@ impl Index {
     pub fn writer<D: Document>(
         &self,
         memory_budget_in_bytes: usize,
-    ) -> crate::Result<IndexWriter<D>> {
+    ) -> crate::Result<IndexWriter<Codec, D>> {
         let mut num_threads = std::cmp::min(available_parallelism()?.get(), MAX_NUM_THREAD);
         let memory_budget_num_bytes_per_thread = memory_budget_in_bytes / num_threads;
         if memory_budget_num_bytes_per_thread < MEMORY_BUDGET_NUM_BYTES_MIN {
@@ -640,7 +716,7 @@ impl Index {
     }
 
     /// Returns the list of segments that are searchable
-    pub fn searchable_segments(&self) -> crate::Result<Vec<Segment>> {
+    pub fn searchable_segments(&self) -> crate::Result<Vec<Segment<Codec>>> {
         Ok(self
             .searchable_segment_metas()?
             .into_iter()
@@ -649,12 +725,12 @@ impl Index {
     }
 
     #[doc(hidden)]
-    pub fn segment(&self, segment_meta: SegmentMeta) -> Segment {
+    pub fn segment(&self, segment_meta: SegmentMeta) -> Segment<Codec> {
         Segment::for_index(self.clone(), segment_meta)
     }
 
     /// Creates a new segment.
-    pub fn new_segment(&self) -> Segment {
+    pub fn new_segment(&self) -> Segment<Codec> {
         let segment_meta = self
             .inventory
             .new_segment_meta(SegmentId::generate_random(), 0);

src/index/index_meta.rs

@@ -7,6 +7,7 @@ use std::sync::Arc;
 use serde::{Deserialize, Serialize};
 
 use super::SegmentComponent;
+use crate::codec::{Codec, CodecConfiguration};
 use crate::index::SegmentId;
 use crate::schema::Schema;
 use crate::store::Compressor;
@@ -320,6 +321,7 @@ pub struct IndexMeta {
     /// This payload is entirely unused by tantivy.
     #[serde(skip_serializing_if = "Option::is_none")]
     pub payload: Option<String>,
+    pub codec: CodecConfiguration,
 }
 
 #[derive(Deserialize, Debug)]
@@ -331,6 +333,8 @@ struct UntrackedIndexMeta {
     pub opstamp: Opstamp,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub payload: Option<String>,
+    #[serde(default)]
+    pub codec: CodecConfiguration,
 }
 
 impl UntrackedIndexMeta {
@@ -345,6 +349,7 @@ impl UntrackedIndexMeta {
             schema: self.schema,
             opstamp: self.opstamp,
             payload: self.payload,
+            codec: self.codec,
         }
     }
 }
@@ -355,13 +360,14 @@ impl IndexMeta {
     ///
     /// This new index does not contains any segments.
     /// Opstamp will the value `0u64`.
-    pub fn with_schema(schema: Schema) -> IndexMeta {
+    pub fn with_schema_and_codec<C: Codec>(schema: Schema, codec: &C) -> IndexMeta {
         IndexMeta {
             index_settings: IndexSettings::default(),
             segments: vec![],
             schema,
             opstamp: 0u64,
             payload: None,
+            codec: CodecConfiguration::from_codec(codec),
         }
     }
 
@@ -412,11 +418,12 @@ mod tests {
             schema,
             opstamp: 0u64,
             payload: None,
+            codec: Default::default(),
         };
         let json = serde_json::ser::to_string(&index_metas).expect("serialization failed");
         assert_eq!(
             json,
-            r#"{"index_settings":{"docstore_compression":"none","docstore_blocksize":16384},"segments":[],"schema":[{"name":"text","type":"text","options":{"indexing":{"record":"position","fieldnorms":true,"tokenizer":"default"},"stored":false,"fast":false}}],"opstamp":0}"#
+            r#"{"index_settings":{"docstore_compression":"none","docstore_blocksize":16384},"segments":[],"schema":[{"name":"text","type":"text","options":{"indexing":{"record":"position","fieldnorms":true,"tokenizer":"default"},"stored":false,"fast":false}}],"opstamp":0,"codec":{"name":"standard"}}"#
         );
 
         let deser_meta: UntrackedIndexMeta = serde_json::from_str(&json).unwrap();

src/index/segment.rs

@@ -2,6 +2,7 @@ use std::fmt;
 use std::path::PathBuf;
 
 use super::SegmentComponent;
+use crate::codec::StandardCodec;
 use crate::directory::error::{OpenReadError, OpenWriteError};
 use crate::directory::{Directory, FileSlice, WritePtr};
 use crate::index::{Index, SegmentId, SegmentMeta};
@@ -10,25 +11,25 @@ use crate::Opstamp;
 
 /// A segment is a piece of the index.
 #[derive(Clone)]
-pub struct Segment {
-    index: Index,
+pub struct Segment<C: crate::codec::Codec = StandardCodec> {
+    index: Index<C>,
     meta: SegmentMeta,
 }
 
-impl fmt::Debug for Segment {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+impl<C: crate::codec::Codec> fmt::Debug for Segment<C> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "Segment({:?})", self.id().uuid_string())
     }
 }
 
-impl Segment {
+impl<C: crate::codec::Codec> Segment<C> {
     /// Creates a new segment given an `Index` and a `SegmentId`
-    pub(crate) fn for_index(index: Index, meta: SegmentMeta) -> Segment {
+    pub(crate) fn for_index(index: Index<C>, meta: SegmentMeta) -> Segment<C> {
         Segment { index, meta }
     }
 
     /// Returns the index the segment belongs to.
-    pub fn index(&self) -> &Index {
+    pub fn index(&self) -> &Index<C> {
         &self.index
     }
 
@@ -46,7 +47,7 @@ impl Segment {
     ///
     /// This method is only used when updating `max_doc` from 0
     /// as we finalize a fresh new segment.
-    pub fn with_max_doc(self, max_doc: u32) -> Segment {
+    pub fn with_max_doc(self, max_doc: u32) -> Segment<C> {
         Segment {
             index: self.index,
             meta: self.meta.with_max_doc(max_doc),
@@ -55,7 +56,7 @@ impl Segment {
 
     #[doc(hidden)]
     #[must_use]
-    pub fn with_delete_meta(self, num_deleted_docs: u32, opstamp: Opstamp) -> Segment {
+    pub fn with_delete_meta(self, num_deleted_docs: u32, opstamp: Opstamp) -> Segment<C> {
         Segment {
             index: self.index,
             meta: self.meta.with_delete_meta(num_deleted_docs, opstamp),

src/index/segment_reader.rs

@@ -140,13 +140,13 @@ impl SegmentReader {
     }
 
     /// Open a new segment for reading.
-    pub fn open(segment: &Segment) -> crate::Result<SegmentReader> {
+    pub fn open<C: crate::codec::Codec>(segment: &Segment<C>) -> crate::Result<SegmentReader> {
         Self::open_with_custom_alive_set(segment, None)
     }
 
     /// Open a new segment for reading.
-    pub fn open_with_custom_alive_set(
-        segment: &Segment,
+    pub fn open_with_custom_alive_set<C: crate::codec::Codec>(
+        segment: &Segment<C>,
         custom_bitset: Option<AliveBitSet>,
     ) -> crate::Result<SegmentReader> {
         let termdict_file = segment.open_read(SegmentComponent::Terms)?;

src/indexer/index_writer.rs

@@ -9,6 +9,7 @@ use smallvec::smallvec;
 use super::operation::{AddOperation, UserOperation};
 use super::segment_updater::SegmentUpdater;
 use super::{AddBatch, AddBatchReceiver, AddBatchSender, PreparedCommit};
+use crate::codec::{Codec, StandardCodec};
 use crate::directory::{DirectoryLock, GarbageCollectionResult, TerminatingWrite};
 use crate::error::TantivyError;
 use crate::fastfield::write_alive_bitset;
@@ -68,12 +69,12 @@ pub struct IndexWriterOptions {
 /// indexing queue.
 /// Each indexing thread builds its own independent [`Segment`], via
 /// a `SegmentWriter` object.
-pub struct IndexWriter<D: Document = TantivyDocument> {
+pub struct IndexWriter<C: Codec = StandardCodec, D: Document = TantivyDocument> {
     // the lock is just used to bind the
     // lifetime of the lock with that of the IndexWriter.
     _directory_lock: Option<DirectoryLock>,
 
-    index: Index,
+    index: Index<C>,
 
     options: IndexWriterOptions,
 
@@ -82,7 +83,7 @@ pub struct IndexWriter<D: Document = TantivyDocument> {
     index_writer_status: IndexWriterStatus<D>,
     operation_sender: AddBatchSender<D>,
 
-    segment_updater: SegmentUpdater,
+    segment_updater: SegmentUpdater<C>,
 
     worker_id: usize,
 
@@ -128,8 +129,8 @@ fn compute_deleted_bitset(
 /// is `==` target_opstamp.
 /// For instance, there was no delete operation between the state of the `segment_entry` and
 /// the `target_opstamp`, `segment_entry` is not updated.
-pub fn advance_deletes(
-    mut segment: Segment,
+pub fn advance_deletes<C: Codec>(
+    mut segment: Segment<C>,
     segment_entry: &mut SegmentEntry,
     target_opstamp: Opstamp,
 ) -> crate::Result<()> {
@@ -179,11 +180,11 @@ pub fn advance_deletes(
     Ok(())
 }
 
-fn index_documents<D: Document>(
+fn index_documents<C: crate::codec::Codec, D: Document>(
     memory_budget: usize,
-    segment: Segment,
+    segment: Segment<C>,
     grouped_document_iterator: &mut dyn Iterator<Item = AddBatch<D>>,
-    segment_updater: &SegmentUpdater,
+    segment_updater: &SegmentUpdater<C>,
     mut delete_cursor: DeleteCursor,
 ) -> crate::Result<()> {
     let mut segment_writer = SegmentWriter::for_segment(memory_budget, segment.clone())?;
@@ -226,8 +227,8 @@ fn index_documents<D: Document>(
 }
 
 /// `doc_opstamps` is required to be non-empty.
-fn apply_deletes(
-    segment: &Segment,
+fn apply_deletes<C: crate::codec::Codec>(
+    segment: &Segment<C>,
     delete_cursor: &mut DeleteCursor,
     doc_opstamps: &[Opstamp],
 ) -> crate::Result<Option<BitSet>> {
@@ -262,7 +263,7 @@ fn apply_deletes(
     })
 }
 
-impl<D: Document> IndexWriter<D> {
+impl<C: Codec, D: Document> IndexWriter<C, D> {
     /// Create a new index writer. Attempts to acquire a lockfile.
     ///
     /// The lockfile should be deleted on drop, but it is possible
@@ -278,7 +279,7 @@ impl<D: Document> IndexWriter<D> {
     /// If the memory arena per thread is too small or too big, returns
     /// `TantivyError::InvalidArgument`
     pub(crate) fn new(
-        index: &Index,
+        index: &Index<C>,
         options: IndexWriterOptions,
         directory_lock: DirectoryLock,
     ) -> crate::Result<Self> {
@@ -345,7 +346,7 @@ impl<D: Document> IndexWriter<D> {
     }
 
     /// Accessor to the index.
-    pub fn index(&self) -> &Index {
+    pub fn index(&self) -> &Index<C> {
         &self.index
     }
 
@@ -393,7 +394,7 @@ impl<D: Document> IndexWriter<D> {
     /// It is safe to start writing file associated with the new `Segment`.
     /// These will not be garbage collected as long as an instance object of
     /// `SegmentMeta` object associated with the new `Segment` is "alive".
-    pub fn new_segment(&self) -> Segment {
+    pub fn new_segment(&self) -> Segment<C> {
         self.index.new_segment()
     }
 
@@ -615,7 +616,7 @@ impl<D: Document> IndexWriter<D> {
     /// It is also possible to add a payload to the `commit`
     /// using this API.
     /// See [`PreparedCommit::set_payload()`].
-    pub fn prepare_commit(&mut self) -> crate::Result<PreparedCommit<'_, D>> {
+    pub fn prepare_commit(&mut self) -> crate::Result<PreparedCommit<'_, C, D>> {
         // Here, because we join all of the worker threads,
         // all of the segment update for this commit have been
         // sent.
@@ -665,7 +666,7 @@ impl<D: Document> IndexWriter<D> {
         self.prepare_commit()?.commit()
     }
 
-    pub(crate) fn segment_updater(&self) -> &SegmentUpdater {
+    pub(crate) fn segment_updater(&self) -> &SegmentUpdater<C> {
         &self.segment_updater
     }
 
@@ -804,7 +805,7 @@ impl<D: Document> IndexWriter<D> {
     }
 }
 
-impl<D: Document> Drop for IndexWriter<D> {
+impl<C: Codec, D: Document> Drop for IndexWriter<C, D> {
     fn drop(&mut self) {
         self.segment_updater.kill();
         self.drop_sender();

src/indexer/merger.rs

@@ -145,7 +145,10 @@ fn extract_fast_field_required_columns(schema: &Schema) -> Vec<(String, ColumnTy
 }
 
 impl IndexMerger {
-    pub fn open(schema: Schema, segments: &[Segment]) -> crate::Result<IndexMerger> {
+    pub fn open<C: crate::codec::Codec>(
+        schema: Schema,
+        segments: &[Segment<C>],
+    ) -> crate::Result<IndexMerger> {
         let alive_bitset = segments.iter().map(|_| None).collect_vec();
         Self::open_with_custom_alive_set(schema, segments, alive_bitset)
     }
@@ -162,9 +165,9 @@ impl IndexMerger {
     // This can be used to merge but also apply an additional filter.
     // One use case is demux, which is basically taking a list of
     // segments and partitions them e.g. by a value in a field.
-    pub fn open_with_custom_alive_set(
+    pub fn open_with_custom_alive_set<C: crate::codec::Codec>(
         schema: Schema,
-        segments: &[Segment],
+        segments: &[Segment<C>],
         alive_bitset_opt: Vec<Option<AliveBitSet>>,
     ) -> crate::Result<IndexMerger> {
         let mut readers = vec![];
@@ -525,7 +528,10 @@ impl IndexMerger {
     ///
     /// # Returns
     /// The number of documents in the resulting segment.
-    pub fn write(&self, mut serializer: SegmentSerializer) -> crate::Result<u32> {
+    pub fn write<C: crate::codec::Codec>(
+        &self,
+        mut serializer: SegmentSerializer<C>,
+    ) -> crate::Result<u32> {
         let doc_id_mapping = self.get_doc_id_from_concatenated_data()?;
         debug!("write-fieldnorms");
         if let Some(fieldnorms_serializer) = serializer.extract_fieldnorms_serializer() {

src/indexer/prepared_commit.rs

@@ -1,16 +1,17 @@
 use super::IndexWriter;
+use crate::codec::Codec;
 use crate::schema::document::Document;
 use crate::{FutureResult, Opstamp, TantivyDocument};
 
 /// A prepared commit
-pub struct PreparedCommit<'a, D: Document = TantivyDocument> {
-    index_writer: &'a mut IndexWriter<D>,
+pub struct PreparedCommit<'a, C: Codec, D: Document = TantivyDocument> {
+    index_writer: &'a mut IndexWriter<C, D>,
     payload: Option<String>,
     opstamp: Opstamp,
 }
 
-impl<'a, D: Document> PreparedCommit<'a, D> {
-    pub(crate) fn new(index_writer: &'a mut IndexWriter<D>, opstamp: Opstamp) -> Self {
+impl<'a, C: Codec, D: Document> PreparedCommit<'a, C, D> {
+    pub(crate) fn new(index_writer: &'a mut IndexWriter<C, D>, opstamp: Opstamp) -> Self {
         Self {
             index_writer,
             payload: None,

src/indexer/segment_serializer.rs

@@ -8,17 +8,17 @@ use crate::store::StoreWriter;
 
 /// Segment serializer is in charge of laying out on disk
 /// the data accumulated and sorted by the `SegmentWriter`.
-pub struct SegmentSerializer {
-    segment: Segment,
+pub struct SegmentSerializer<C: crate::codec::Codec> {
+    segment: Segment<C>,
     pub(crate) store_writer: StoreWriter,
     fast_field_write: WritePtr,
     fieldnorms_serializer: Option<FieldNormsSerializer>,
     postings_serializer: InvertedIndexSerializer,
 }
 
-impl SegmentSerializer {
+impl<C: crate::codec::Codec> SegmentSerializer<C> {
     /// Creates a new `SegmentSerializer`.
-    pub fn for_segment(mut segment: Segment) -> crate::Result<SegmentSerializer> {
+    pub fn for_segment(mut segment: Segment<C>) -> crate::Result<SegmentSerializer<C>> {
         let settings = segment.index().settings().clone();
         let store_writer = {
             let store_write = segment.open_write(SegmentComponent::Store)?;
@@ -50,7 +50,7 @@ impl SegmentSerializer {
         self.store_writer.mem_usage()
     }
 
-    pub fn segment(&self) -> &Segment {
+    pub fn segment(&self) -> &Segment<C> {
         &self.segment
     }
 

src/indexer/segment_updater.rs

@@ -10,6 +10,7 @@ use std::sync::{Arc, RwLock};
 use rayon::{ThreadPool, ThreadPoolBuilder};
 
 use super::segment_manager::SegmentManager;
+use crate::codec::{Codec, CodecConfiguration};
 use crate::core::META_FILEPATH;
 use crate::directory::{Directory, DirectoryClone, GarbageCollectionResult};
 use crate::fastfield::AliveBitSet;
@@ -61,10 +62,10 @@ pub(crate) fn save_metas(metas: &IndexMeta, directory: &dyn Directory) -> crate:
 // We voluntarily pass a merge_operation ref to guarantee that
 // the merge_operation is alive during the process
 #[derive(Clone)]
-pub(crate) struct SegmentUpdater(Arc<InnerSegmentUpdater>);
+pub(crate) struct SegmentUpdater<C: Codec>(Arc<InnerSegmentUpdater<C>>);
 
-impl Deref for SegmentUpdater {
-    type Target = InnerSegmentUpdater;
+impl<C: Codec> Deref for SegmentUpdater<C> {
+    type Target = InnerSegmentUpdater<C>;
 
     #[inline]
     fn deref(&self) -> &Self::Target {
@@ -72,8 +73,8 @@ impl Deref for SegmentUpdater {
     }
 }
 
-fn garbage_collect_files(
-    segment_updater: SegmentUpdater,
+fn garbage_collect_files<C: Codec>(
+    segment_updater: SegmentUpdater<C>,
 ) -> crate::Result<GarbageCollectionResult> {
     info!("Running garbage collection");
     let mut index = segment_updater.index.clone();
@@ -84,8 +85,8 @@ fn garbage_collect_files(
 
 /// Merges a list of segments the list of segment givens in the `segment_entries`.
 /// This function happens in the calling thread and is computationally expensive.
-fn merge(
-    index: &Index,
+fn merge<Codec: crate::codec::Codec>(
+    index: &Index<Codec>,
     mut segment_entries: Vec<SegmentEntry>,
     target_opstamp: Opstamp,
 ) -> crate::Result<Option<SegmentEntry>> {
@@ -108,7 +109,7 @@ fn merge(
 
     let delete_cursor = segment_entries[0].delete_cursor().clone();
 
-    let segments: Vec<Segment> = segment_entries
+    let segments: Vec<Segment<Codec>> = segment_entries
         .iter()
         .map(|segment_entry| index.segment(segment_entry.meta().clone()))
         .collect();
@@ -139,10 +140,10 @@ fn merge(
 /// meant to work if you have an `IndexWriter` running for the origin indices, or
 /// the destination `Index`.
 #[doc(hidden)]
-pub fn merge_indices<T: Into<Box<dyn Directory>>>(
-    indices: &[Index],
-    output_directory: T,
-) -> crate::Result<Index> {
+pub fn merge_indices<Codec: crate::codec::Codec>(
+    indices: &[Index<Codec>],
+    output_directory: Box<dyn Directory>,
+) -> crate::Result<Index<Codec>> {
     if indices.is_empty() {
         // If there are no indices to merge, there is no need to do anything.
         return Err(crate::TantivyError::InvalidArgument(
@@ -163,7 +164,7 @@ pub fn merge_indices<T: Into<Box<dyn Directory>>>(
         ));
     }
 
-    let mut segments: Vec<Segment> = Vec::new();
+    let mut segments: Vec<Segment<Codec>> = Vec::new();
     for index in indices {
         segments.extend(index.searchable_segments()?);
     }
@@ -185,12 +186,12 @@ pub fn merge_indices<T: Into<Box<dyn Directory>>>(
 /// meant to work if you have an `IndexWriter` running for the origin indices, or
 /// the destination `Index`.
 #[doc(hidden)]
-pub fn merge_filtered_segments<T: Into<Box<dyn Directory>>>(
-    segments: &[Segment],
+pub fn merge_filtered_segments<Codec: crate::codec::Codec, T: Into<Box<dyn Directory>>>(
+    segments: &[Segment<Codec>],
     target_settings: IndexSettings,
     filter_doc_ids: Vec<Option<AliveBitSet>>,
     output_directory: T,
-) -> crate::Result<Index> {
+) -> crate::Result<Index<Codec>> {
     if segments.is_empty() {
         // If there are no indices to merge, there is no need to do anything.
         return Err(crate::TantivyError::InvalidArgument(
@@ -211,11 +212,12 @@ pub fn merge_filtered_segments<T: Into<Box<dyn Directory>>>(
         ));
     }
 
-    let mut merged_index = Index::create(
-        output_directory,
-        target_schema.clone(),
-        target_settings.clone(),
-    )?;
+    let mut merged_index: Index<Codec> = Index::builder()
+        .schema(target_schema.clone())
+        .codec(segments[0].index().codec().clone())
+        .settings(target_settings.clone())
+        .create(output_directory.into())?;
+
     let merged_segment = merged_index.new_segment();
     let merged_segment_id = merged_segment.id();
     let merger: IndexMerger =
@@ -235,6 +237,7 @@ pub fn merge_filtered_segments<T: Into<Box<dyn Directory>>>(
             ))
             .trim_end()
     );
+    let codec_configuration = CodecConfiguration::from_codec(segments[0].index().codec());
 
     let index_meta = IndexMeta {
         index_settings: target_settings, // index_settings of all segments should be the same
@@ -242,6 +245,7 @@ pub fn merge_filtered_segments<T: Into<Box<dyn Directory>>>(
         schema: target_schema,
         opstamp: 0u64,
         payload: Some(stats),
+        codec: codec_configuration,
     };
 
     // save the meta.json
@@ -250,7 +254,7 @@ pub fn merge_filtered_segments<T: Into<Box<dyn Directory>>>(
     Ok(merged_index)
 }
 
-pub(crate) struct InnerSegmentUpdater {
+pub(crate) struct InnerSegmentUpdater<C: Codec> {
     // we keep a copy of the current active IndexMeta to
     // avoid loading the file every time we need it in the
     // `SegmentUpdater`.
@@ -261,7 +265,7 @@ pub(crate) struct InnerSegmentUpdater {
     pool: ThreadPool,
     merge_thread_pool: ThreadPool,
 
-    index: Index,
+    index: Index<C>,
     segment_manager: SegmentManager,
     merge_policy: RwLock<Arc<dyn MergePolicy>>,
     killed: AtomicBool,
@@ -269,13 +273,13 @@ pub(crate) struct InnerSegmentUpdater {
     merge_operations: MergeOperationInventory,
 }
 
-impl SegmentUpdater {
+impl<Codec: crate::codec::Codec> SegmentUpdater<Codec> {
     pub fn create(
-        index: Index,
+        index: Index<Codec>,
         stamper: Stamper,
         delete_cursor: &DeleteCursor,
         num_merge_threads: usize,
-    ) -> crate::Result<SegmentUpdater> {
+    ) -> crate::Result<Self> {
         let segments = index.searchable_segment_metas()?;
         let segment_manager = SegmentManager::from_segments(segments, delete_cursor);
         let pool = ThreadPoolBuilder::new()
@@ -404,12 +408,14 @@ impl SegmentUpdater {
             //
             // Segment 1 from disk 1, Segment 1 from disk 2, etc.
             committed_segment_metas.sort_by_key(|segment_meta| -(segment_meta.max_doc() as i32));
+            let codec = CodecConfiguration::from_codec(index.codec());
             let index_meta = IndexMeta {
                 index_settings: index.settings().clone(),
                 segments: committed_segment_metas,
                 schema: index.schema(),
                 opstamp,
                 payload: commit_message,
+                codec,
             };
             // TODO add context to the error.
             save_metas(&index_meta, directory.box_clone().borrow_mut())?;
@@ -443,7 +449,7 @@ impl SegmentUpdater {
         opstamp: Opstamp,
         payload: Option<String>,
     ) -> FutureResult<Opstamp> {
-        let segment_updater: SegmentUpdater = self.clone();
+        let segment_updater: SegmentUpdater<Codec> = self.clone();
         self.schedule_task(move || {
             let segment_entries = segment_updater.purge_deletes(opstamp)?;
             segment_updater.segment_manager.commit(segment_entries);
@@ -702,6 +708,7 @@ impl SegmentUpdater {
 #[cfg(test)]
 mod tests {
     use super::merge_indices;
+    use crate::codec::StandardCodec;
     use crate::collector::TopDocs;
     use crate::directory::RamDirectory;
     use crate::fastfield::AliveBitSet;
@@ -915,7 +922,7 @@ mod tests {
 
     #[test]
     fn test_merge_empty_indices_array() {
-        let merge_result = merge_indices(&[], RamDirectory::default());
+        let merge_result = merge_indices::<StandardCodec>(&[], Box::new(RamDirectory::default()));
         assert!(merge_result.is_err());
     }
 
@@ -942,7 +949,10 @@ mod tests {
         };
 
         // mismatched schema index list
-        let result = merge_indices(&[first_index, second_index], RamDirectory::default());
+        let result = merge_indices(
+            &[first_index, second_index],
+            Box::new(RamDirectory::default()),
+        );
         assert!(result.is_err());
 
         Ok(())

src/indexer/segment_writer.rs

@@ -4,6 +4,7 @@ use itertools::Itertools;
 use tokenizer_api::BoxTokenStream;
 
 use super::operation::AddOperation;
+use crate::codec::Codec;
 use crate::fastfield::FastFieldsWriter;
 use crate::fieldnorm::{FieldNormReaders, FieldNormsWriter};
 use crate::index::{Segment, SegmentComponent};
@@ -45,11 +46,11 @@ fn compute_initial_table_size(per_thread_memory_budget: usize) -> crate::Result<
 ///
 /// They creates the postings list in anonymous memory.
 /// The segment is laid on disk when the segment gets `finalized`.
-pub struct SegmentWriter {
+pub struct SegmentWriter<Codec: crate::codec::Codec> {
     pub(crate) max_doc: DocId,
     pub(crate) ctx: IndexingContext,
     pub(crate) per_field_postings_writers: PerFieldPostingsWriter,
-    pub(crate) segment_serializer: SegmentSerializer,
+    pub(crate) segment_serializer: SegmentSerializer<Codec>,
     pub(crate) fast_field_writers: FastFieldsWriter,
     pub(crate) fieldnorms_writer: FieldNormsWriter,
     pub(crate) json_path_writer: JsonPathWriter,
@@ -60,7 +61,7 @@ pub struct SegmentWriter {
     schema: Schema,
 }
 
-impl SegmentWriter {
+impl<Codec: crate::codec::Codec> SegmentWriter<Codec> {
     /// Creates a new `SegmentWriter`
     ///
     /// The arguments are defined as follows
@@ -70,7 +71,10 @@ impl SegmentWriter {
     ///   behavior as a memory limit.
     /// - segment: The segment being written
     /// - schema
-    pub fn for_segment(memory_budget_in_bytes: usize, segment: Segment) -> crate::Result<Self> {
+    pub fn for_segment(
+        memory_budget_in_bytes: usize,
+        segment: Segment<Codec>,
+    ) -> crate::Result<Self> {
         let schema = segment.schema();
         let tokenizer_manager = segment.index().tokenizers().clone();
         let tokenizer_manager_fast_field = segment.index().fast_field_tokenizer().clone();
@@ -386,13 +390,13 @@ impl SegmentWriter {
 /// to the `SegmentSerializer`.
 ///
 /// `doc_id_map` is used to map to the new doc_id order.
-fn remap_and_write(
+fn remap_and_write<C: Codec>(
     schema: Schema,
     per_field_postings_writers: &PerFieldPostingsWriter,
     ctx: IndexingContext,
     fast_field_writers: FastFieldsWriter,
     fieldnorms_writer: &FieldNormsWriter,
-    mut serializer: SegmentSerializer,
+    mut serializer: SegmentSerializer<C>,
 ) -> crate::Result<()> {
     debug!("remap-and-write");
     if let Some(fieldnorms_serializer) = serializer.extract_fieldnorms_serializer() {

src/indexer/single_segment_index_writer.rs

@@ -1,5 +1,6 @@
 use std::marker::PhantomData;
 
+use crate::codec::CodecConfiguration;
 use crate::indexer::operation::AddOperation;
 use crate::indexer::segment_updater::save_metas;
 use crate::indexer::SegmentWriter;
@@ -7,22 +8,22 @@ use crate::schema::document::Document;
 use crate::{Directory, Index, IndexMeta, Opstamp, Segment, TantivyDocument};
 
 #[doc(hidden)]
-pub struct SingleSegmentIndexWriter<D: Document = TantivyDocument> {
-    segment_writer: SegmentWriter,
-    segment: Segment,
+pub struct SingleSegmentIndexWriter<Codec: crate::codec::Codec, D: Document = TantivyDocument> {
+    segment_writer: SegmentWriter<Codec>,
+    segment: Segment<Codec>,
     opstamp: Opstamp,
-    _phantom: PhantomData<D>,
+    _doc: PhantomData<D>,
 }
 
-impl<D: Document> SingleSegmentIndexWriter<D> {
-    pub fn new(index: Index, mem_budget: usize) -> crate::Result<Self> {
+impl<Codec: crate::codec::Codec, D: Document> SingleSegmentIndexWriter<Codec, D> {
+    pub fn new(index: Index<Codec>, mem_budget: usize) -> crate::Result<Self> {
         let segment = index.new_segment();
         let segment_writer = SegmentWriter::for_segment(mem_budget, segment.clone())?;
         Ok(Self {
             segment_writer,
             segment,
             opstamp: 0,
-            _phantom: PhantomData,
+            _doc: PhantomData,
         })
     }
 
@@ -37,10 +38,10 @@ impl<D: Document> SingleSegmentIndexWriter<D> {
             .add_document(AddOperation { opstamp, document })
     }
 
-    pub fn finalize(self) -> crate::Result<Index> {
+    pub fn finalize(self) -> crate::Result<Index<Codec>> {
         let max_doc = self.segment_writer.max_doc();
         self.segment_writer.finalize()?;
-        let segment: Segment = self.segment.with_max_doc(max_doc);
+        let segment: Segment<Codec> = self.segment.with_max_doc(max_doc);
         let index = segment.index();
         let index_meta = IndexMeta {
             index_settings: index.settings().clone(),
@@ -48,6 +49,7 @@ impl<D: Document> SingleSegmentIndexWriter<D> {
             schema: index.schema(),
             opstamp: 0,
             payload: None,
+            codec: CodecConfiguration::from_codec(index.codec()),
         };
         save_metas(&index_meta, index.directory())?;
         index.directory().sync_directory()?;

src/lib.rs

@@ -166,6 +166,7 @@ mod functional_test;
 
 #[macro_use]
 mod macros;
+pub mod codec;
 mod future_result;
 
 // Re-exports

src/postings/json_postings_writer.rs

@@ -22,12 +22,6 @@ pub(crate) struct JsonPostingsWriter<Rec: Recorder> {
     non_str_posting_writer: SpecializedPostingsWriter<DocIdRecorder>,
 }
 
-impl<Rec: Recorder> From<JsonPostingsWriter<Rec>> for Box<dyn PostingsWriter> {
-    fn from(json_postings_writer: JsonPostingsWriter<Rec>) -> Box<dyn PostingsWriter> {
-        Box::new(json_postings_writer)
-    }
-}
-
 impl<Rec: Recorder> PostingsWriter for JsonPostingsWriter<Rec> {
     #[inline]
     fn subscribe(

src/postings/per_field_postings_writer.rs

@@ -1,16 +1,15 @@
 use crate::postings::json_postings_writer::JsonPostingsWriter;
-use crate::postings::postings_writer::SpecializedPostingsWriter;
+use crate::postings::postings_writer::{PostingsWriterEnum, SpecializedPostingsWriter};
 use crate::postings::recorder::{DocIdRecorder, TermFrequencyRecorder, TfAndPositionRecorder};
-use crate::postings::PostingsWriter;
 use crate::schema::{Field, FieldEntry, FieldType, IndexRecordOption, Schema};
 
 pub(crate) struct PerFieldPostingsWriter {
-    per_field_postings_writers: Vec<Box<dyn PostingsWriter>>,
+    per_field_postings_writers: Vec<PostingsWriterEnum>,
 }
 
 impl PerFieldPostingsWriter {
     pub fn for_schema(schema: &Schema) -> Self {
-        let per_field_postings_writers = schema
+        let per_field_postings_writers: Vec<PostingsWriterEnum> = schema
             .fields()
             .map(|(_, field_entry)| posting_writer_from_field_entry(field_entry))
             .collect();
@@ -19,16 +18,16 @@ impl PerFieldPostingsWriter {
         }
     }
 
-    pub(crate) fn get_for_field(&self, field: Field) -> &dyn PostingsWriter {
-        self.per_field_postings_writers[field.field_id() as usize].as_ref()
+    pub(crate) fn get_for_field(&self, field: Field) -> &PostingsWriterEnum {
+        &self.per_field_postings_writers[field.field_id() as usize]
     }
 
-    pub(crate) fn get_for_field_mut(&mut self, field: Field) -> &mut dyn PostingsWriter {
-        self.per_field_postings_writers[field.field_id() as usize].as_mut()
+    pub(crate) fn get_for_field_mut(&mut self, field: Field) -> &mut PostingsWriterEnum {
+        &mut self.per_field_postings_writers[field.field_id() as usize]
     }
 }
 
-fn posting_writer_from_field_entry(field_entry: &FieldEntry) -> Box<dyn PostingsWriter> {
+fn posting_writer_from_field_entry(field_entry: &FieldEntry) -> PostingsWriterEnum {
     match *field_entry.field_type() {
         FieldType::Str(ref text_options) => text_options
             .get_indexing_options()
@@ -51,7 +50,7 @@ fn posting_writer_from_field_entry(field_entry: &FieldEntry) -> Box<dyn Postings
         | FieldType::Date(_)
         | FieldType::Bytes(_)
         | FieldType::IpAddr(_)
-        | FieldType::Facet(_) => Box::<SpecializedPostingsWriter<DocIdRecorder>>::default(),
+        | FieldType::Facet(_) => <SpecializedPostingsWriter<DocIdRecorder>>::default().into(),
         FieldType::JsonObject(ref json_object_options) => {
             if let Some(text_indexing_option) = json_object_options.get_text_indexing_options() {
                 match text_indexing_option.index_option() {

src/postings/postings_writer.rs

@@ -7,7 +7,10 @@ use stacker::Addr;
 use crate::fieldnorm::FieldNormReaders;
 use crate::indexer::indexing_term::IndexingTerm;
 use crate::indexer::path_to_unordered_id::OrderedPathId;
-use crate::postings::recorder::{BufferLender, Recorder};
+use crate::postings::json_postings_writer::JsonPostingsWriter;
+use crate::postings::recorder::{
+    BufferLender, DocIdRecorder, Recorder, TermFrequencyRecorder, TfAndPositionRecorder,
+};
 use crate::postings::{
     FieldSerializer, IndexingContext, InvertedIndexSerializer, PerFieldPostingsWriter,
 };
@@ -100,6 +103,141 @@ pub(crate) struct IndexingPosition {
     pub end_position: u32,
 }
 
+pub enum PostingsWriterEnum {
+    DocId(SpecializedPostingsWriter<DocIdRecorder>),
+    DocIdTf(SpecializedPostingsWriter<TermFrequencyRecorder>),
+    DocTfAndPosition(SpecializedPostingsWriter<TfAndPositionRecorder>),
+    JsonDocId(JsonPostingsWriter<DocIdRecorder>),
+    JsonDocIdTf(JsonPostingsWriter<TermFrequencyRecorder>),
+    JsonDocTfAndPosition(JsonPostingsWriter<TfAndPositionRecorder>),
+}
+
+impl From<SpecializedPostingsWriter<DocIdRecorder>> for PostingsWriterEnum {
+    fn from(doc_id_recorder_writer: SpecializedPostingsWriter<DocIdRecorder>) -> Self {
+        PostingsWriterEnum::DocId(doc_id_recorder_writer)
+    }
+}
+
+impl From<SpecializedPostingsWriter<TermFrequencyRecorder>> for PostingsWriterEnum {
+    fn from(doc_id_tf_recorder_writer: SpecializedPostingsWriter<TermFrequencyRecorder>) -> Self {
+        PostingsWriterEnum::DocIdTf(doc_id_tf_recorder_writer)
+    }
+}
+
+impl From<SpecializedPostingsWriter<TfAndPositionRecorder>> for PostingsWriterEnum {
+    fn from(
+        doc_id_tf_and_positions_recorder_writer: SpecializedPostingsWriter<TfAndPositionRecorder>,
+    ) -> Self {
+        PostingsWriterEnum::DocTfAndPosition(doc_id_tf_and_positions_recorder_writer)
+    }
+}
+
+impl From<JsonPostingsWriter<DocIdRecorder>> for PostingsWriterEnum {
+    fn from(doc_id_recorder_writer: JsonPostingsWriter<DocIdRecorder>) -> Self {
+        PostingsWriterEnum::JsonDocId(doc_id_recorder_writer)
+    }
+}
+
+impl From<JsonPostingsWriter<TermFrequencyRecorder>> for PostingsWriterEnum {
+    fn from(doc_id_tf_recorder_writer: JsonPostingsWriter<TermFrequencyRecorder>) -> Self {
+        PostingsWriterEnum::JsonDocIdTf(doc_id_tf_recorder_writer)
+    }
+}
+
+impl From<JsonPostingsWriter<TfAndPositionRecorder>> for PostingsWriterEnum {
+    fn from(
+        doc_id_tf_and_positions_recorder_writer: JsonPostingsWriter<TfAndPositionRecorder>,
+    ) -> Self {
+        PostingsWriterEnum::JsonDocTfAndPosition(doc_id_tf_and_positions_recorder_writer)
+    }
+}
+
+impl PostingsWriter for PostingsWriterEnum {
+    fn subscribe(&mut self, doc: DocId, pos: u32, term: &IndexingTerm, ctx: &mut IndexingContext) {
+        match self {
+            PostingsWriterEnum::DocId(writer) => writer.subscribe(doc, pos, term, ctx),
+            PostingsWriterEnum::DocIdTf(writer) => writer.subscribe(doc, pos, term, ctx),
+            PostingsWriterEnum::DocTfAndPosition(writer) => writer.subscribe(doc, pos, term, ctx),
+            PostingsWriterEnum::JsonDocId(writer) => writer.subscribe(doc, pos, term, ctx),
+            PostingsWriterEnum::JsonDocIdTf(writer) => writer.subscribe(doc, pos, term, ctx),
+            PostingsWriterEnum::JsonDocTfAndPosition(writer) => {
+                writer.subscribe(doc, pos, term, ctx)
+            }
+        }
+    }
+
+    fn serialize(
+        &self,
+        term_addrs: &[(Field, OrderedPathId, &[u8], Addr)],
+        ordered_id_to_path: &[&str],
+        ctx: &IndexingContext,
+        serializer: &mut FieldSerializer,
+    ) -> io::Result<()> {
+        match self {
+            PostingsWriterEnum::DocId(writer) => {
+                writer.serialize(term_addrs, ordered_id_to_path, ctx, serializer)
+            }
+            PostingsWriterEnum::DocIdTf(writer) => {
+                writer.serialize(term_addrs, ordered_id_to_path, ctx, serializer)
+            }
+            PostingsWriterEnum::DocTfAndPosition(writer) => {
+                writer.serialize(term_addrs, ordered_id_to_path, ctx, serializer)
+            }
+            PostingsWriterEnum::JsonDocId(writer) => {
+                writer.serialize(term_addrs, ordered_id_to_path, ctx, serializer)
+            }
+            PostingsWriterEnum::JsonDocIdTf(writer) => {
+                writer.serialize(term_addrs, ordered_id_to_path, ctx, serializer)
+            }
+            PostingsWriterEnum::JsonDocTfAndPosition(writer) => {
+                writer.serialize(term_addrs, ordered_id_to_path, ctx, serializer)
+            }
+        }
+    }
+
+    /// Tokenize a text and subscribe all of its token.
+    fn index_text(
+        &mut self,
+        doc_id: DocId,
+        token_stream: &mut dyn TokenStream,
+        term_buffer: &mut IndexingTerm,
+        ctx: &mut IndexingContext,
+        indexing_position: &mut IndexingPosition,
+    ) {
+        match self {
+            PostingsWriterEnum::DocId(writer) => {
+                writer.index_text(doc_id, token_stream, term_buffer, ctx, indexing_position)
+            }
+            PostingsWriterEnum::DocIdTf(writer) => {
+                writer.index_text(doc_id, token_stream, term_buffer, ctx, indexing_position)
+            }
+            PostingsWriterEnum::DocTfAndPosition(writer) => {
+                writer.index_text(doc_id, token_stream, term_buffer, ctx, indexing_position)
+            }
+            PostingsWriterEnum::JsonDocId(writer) => {
+                writer.index_text(doc_id, token_stream, term_buffer, ctx, indexing_position)
+            }
+            PostingsWriterEnum::JsonDocIdTf(writer) => {
+                writer.index_text(doc_id, token_stream, term_buffer, ctx, indexing_position)
+            }
+            PostingsWriterEnum::JsonDocTfAndPosition(writer) => {
+                writer.index_text(doc_id, token_stream, term_buffer, ctx, indexing_position)
+            }
+        }
+    }
+
+    fn total_num_tokens(&self) -> u64 {
+        match self {
+            PostingsWriterEnum::DocId(writer) => writer.total_num_tokens(),
+            PostingsWriterEnum::DocIdTf(writer) => writer.total_num_tokens(),
+            PostingsWriterEnum::DocTfAndPosition(writer) => writer.total_num_tokens(),
+            PostingsWriterEnum::JsonDocId(writer) => writer.total_num_tokens(),
+            PostingsWriterEnum::JsonDocIdTf(writer) => writer.total_num_tokens(),
+            PostingsWriterEnum::JsonDocTfAndPosition(writer) => writer.total_num_tokens(),
+        }
+    }
+}
+
 /// The `PostingsWriter` is in charge of receiving documenting
 /// and building a `Segment` in anonymous memory.
 ///
@@ -171,14 +309,6 @@ pub(crate) struct SpecializedPostingsWriter<Rec: Recorder> {
     _recorder_type: PhantomData<Rec>,
 }
 
-impl<Rec: Recorder> From<SpecializedPostingsWriter<Rec>> for Box<dyn PostingsWriter> {
-    fn from(
-        specialized_postings_writer: SpecializedPostingsWriter<Rec>,
-    ) -> Box<dyn PostingsWriter> {
-        Box::new(specialized_postings_writer)
-    }
-}
-
 impl<Rec: Recorder> SpecializedPostingsWriter<Rec> {
     #[inline]
     pub(crate) fn serialize_one_term(

src/postings/segment_postings.rs

@@ -70,13 +70,13 @@ impl SegmentPostings {
         let mut buffer = Vec::new();
         {
             let mut postings_serializer =
-                PostingsSerializer::new(&mut buffer, 0.0, IndexRecordOption::Basic, None);
+                PostingsSerializer::new(0.0, IndexRecordOption::Basic, None);
             postings_serializer.new_term(docs.len() as u32, false);
             for &doc in docs {
                 postings_serializer.write_doc(doc, 1u32);
             }
             postings_serializer
-                .close_term(docs.len() as u32)
+                .close_term(docs.len() as u32, &mut buffer)
                 .expect("In memory Serialization should never fail.");
         }
         let block_segment_postings = BlockSegmentPostings::open(
@@ -115,7 +115,6 @@ impl SegmentPostings {
             })
             .unwrap_or(0.0);
         let mut postings_serializer = PostingsSerializer::new(
-            &mut buffer,
             average_field_norm,
             IndexRecordOption::WithFreqs,
             fieldnorm_reader,
@@ -125,7 +124,7 @@ impl SegmentPostings {
             postings_serializer.write_doc(doc, tf);
         }
         postings_serializer
-            .close_term(doc_and_tfs.len() as u32)
+            .close_term(doc_and_tfs.len() as u32, &mut buffer)
             .unwrap();
         let block_segment_postings = BlockSegmentPostings::open(
             doc_and_tfs.len() as u32,

src/postings/serializer.rs

@@ -55,7 +55,9 @@ pub struct InvertedIndexSerializer {
 
 impl InvertedIndexSerializer {
     /// Open a new `InvertedIndexSerializer` for the given segment
-    pub fn open(segment: &mut Segment) -> crate::Result<InvertedIndexSerializer> {
+    pub fn open<C: crate::codec::Codec>(
+        segment: &mut Segment<C>,
+    ) -> crate::Result<InvertedIndexSerializer> {
         use crate::index::SegmentComponent::{Positions, Postings, Terms};
         let inv_index_serializer = InvertedIndexSerializer {
             terms_write: CompositeWrite::wrap(segment.open_write(Terms)?),
@@ -104,10 +106,12 @@ impl InvertedIndexSerializer {
 /// the serialization of a specific field.
 pub struct FieldSerializer<'a> {
     term_dictionary_builder: TermDictionaryBuilder<&'a mut CountingWriter<WritePtr>>,
-    postings_serializer: PostingsSerializer<&'a mut CountingWriter<WritePtr>>,
+    postings_serializer: PostingsSerializer,
     positions_serializer_opt: Option<PositionSerializer<&'a mut CountingWriter<WritePtr>>>,
     current_term_info: TermInfo,
     term_open: bool,
+    postings_write: &'a mut CountingWriter<WritePtr>,
+    postings_start_offset: u64,
 }
 
 impl<'a> FieldSerializer<'a> {
@@ -128,27 +132,30 @@ impl<'a> FieldSerializer<'a> {
             .as_ref()
             .map(|ff_reader| total_num_tokens as Score / ff_reader.num_docs() as Score)
             .unwrap_or(0.0);
-        let postings_serializer = PostingsSerializer::new(
-            postings_write,
-            average_fieldnorm,
-            index_record_option,
-            fieldnorm_reader,
-        );
+        let postings_serializer =
+            PostingsSerializer::new(average_fieldnorm, index_record_option, fieldnorm_reader);
         let positions_serializer_opt = if index_record_option.has_positions() {
             Some(PositionSerializer::new(positions_write))
         } else {
             None
         };
 
+        let postings_start_offset = postings_write.written_bytes();
         Ok(FieldSerializer {
             term_dictionary_builder,
             postings_serializer,
             positions_serializer_opt,
             current_term_info: TermInfo::default(),
             term_open: false,
+            postings_write,
+            postings_start_offset,
         })
     }
 
+    fn postings_offset(&self) -> usize {
+        (self.postings_write.written_bytes() - self.postings_start_offset) as usize
+    }
+
     fn current_term_info(&self) -> TermInfo {
         let positions_start =
             if let Some(positions_serializer) = self.positions_serializer_opt.as_ref() {
@@ -156,7 +163,7 @@ impl<'a> FieldSerializer<'a> {
             } else {
                 0u64
             } as usize;
-        let addr = self.postings_serializer.written_bytes() as usize;
+        let addr = self.postings_offset();
         TermInfo {
             doc_freq: 0,
             postings_range: addr..addr,
@@ -213,21 +220,22 @@ impl<'a> FieldSerializer<'a> {
         crate::fail_point!("FieldSerializer::close_term", |msg: Option<String>| {
             Err(io::Error::new(io::ErrorKind::Other, format!("{msg:?}")))
         });
-        if self.term_open {
-            self.postings_serializer
-                .close_term(self.current_term_info.doc_freq)?;
-            self.current_term_info.postings_range.end =
-                self.postings_serializer.written_bytes() as usize;
 
-            if let Some(positions_serializer) = self.positions_serializer_opt.as_mut() {
-                positions_serializer.close_term()?;
-                self.current_term_info.positions_range.end =
-                    positions_serializer.written_bytes() as usize;
-            }
-            self.term_dictionary_builder
-                .insert_value(&self.current_term_info)?;
-            self.term_open = false;
+        if !self.term_open {
+            return Ok(());
+        };
+
+        self.postings_serializer
+            .close_term(self.current_term_info.doc_freq, self.postings_write)?;
+        self.current_term_info.postings_range.end = self.postings_offset();
+        if let Some(positions_serializer) = self.positions_serializer_opt.as_mut() {
+            positions_serializer.close_term()?;
+            self.current_term_info.positions_range.end =
+                positions_serializer.written_bytes() as usize;
         }
+        self.term_dictionary_builder
+            .insert_value(&self.current_term_info)?;
+        self.term_open = false;
         Ok(())
     }
 
@@ -237,7 +245,7 @@ impl<'a> FieldSerializer<'a> {
         if let Some(positions_serializer) = self.positions_serializer_opt {
             positions_serializer.close()?;
         }
-        self.postings_serializer.close()?;
+        self.postings_write.flush()?;
         self.term_dictionary_builder.finish()?;
         Ok(())
     }
@@ -291,8 +299,7 @@ impl Block {
     }
 }
 
-pub struct PostingsSerializer<W: Write> {
-    output_write: CountingWriter<W>,
+pub struct PostingsSerializer {
     last_doc_id_encoded: u32,
 
     block_encoder: BlockEncoder,
@@ -310,16 +317,13 @@ pub struct PostingsSerializer<W: Write> {
     term_has_freq: bool,
 }
 
-impl<W: Write> PostingsSerializer<W> {
+impl PostingsSerializer {
     pub fn new(
-        write: W,
         avg_fieldnorm: Score,
         mode: IndexRecordOption,
         fieldnorm_reader: Option<FieldNormReader>,
-    ) -> PostingsSerializer<W> {
+    ) -> PostingsSerializer {
         PostingsSerializer {
-            output_write: CountingWriter::wrap(write),
-
             block_encoder: BlockEncoder::new(),
             block: Box::new(Block::new()),
 
@@ -422,11 +426,11 @@ impl<W: Write> PostingsSerializer<W> {
         }
     }
 
-    fn close(mut self) -> io::Result<()> {
-        self.postings_write.flush()
-    }
-
-    pub fn close_term(&mut self, doc_freq: u32) -> io::Result<()> {
+    pub fn close_term(
+        &mut self,
+        doc_freq: u32,
+        output_write: &mut impl std::io::Write,
+    ) -> io::Result<()> {
         if !self.block.is_empty() {
             // we have doc ids waiting to be written
             // this happens when the number of doc ids is
@@ -451,26 +455,16 @@ impl<W: Write> PostingsSerializer<W> {
         }
         if doc_freq >= COMPRESSION_BLOCK_SIZE as u32 {
             let skip_data = self.skip_write.data();
-            VInt(skip_data.len() as u64).serialize(&mut self.output_write)?;
-            self.output_write.write_all(skip_data)?;
+            VInt(skip_data.len() as u64).serialize(output_write)?;
+            output_write.write_all(skip_data)?;
         }
-        self.output_write.write_all(&self.postings_write[..])?;
+        output_write.write_all(&self.postings_write[..])?;
         self.skip_write.clear();
         self.postings_write.clear();
         self.bm25_weight = None;
         Ok(())
     }
 
-    /// Returns the number of bytes written in the postings write object
-    /// at this point.
-    /// When called before writing the postings of a term, this value is used as
-    /// start offset.
-    /// When called after writing the postings of a term, this value is used as a
-    /// end offset.
-    fn written_bytes(&self) -> u64 {
-        self.output_write.written_bytes()
-    }
-
     fn clear(&mut self) {
         self.block.clear();
         self.last_doc_id_encoded = 0;

src/reader/mod.rs

@@ -7,6 +7,7 @@ use arc_swap::ArcSwap;
 pub use warming::Warmer;
 
 use self::warming::WarmingState;
+use crate::codec::Codec;
 use crate::core::searcher::{SearcherGeneration, SearcherInner};
 use crate::directory::{Directory, WatchCallback, WatchHandle, META_LOCK};
 use crate::store::DOCSTORE_CACHE_CAPACITY;
@@ -38,17 +39,17 @@ pub enum ReloadPolicy {
 /// - number of warming threads, for parallelizing warming work
 /// - The cache size of the underlying doc store readers.
 #[derive(Clone)]
-pub struct IndexReaderBuilder {
+pub struct IndexReaderBuilder<C: Codec = crate::codec::StandardCodec> {
     reload_policy: ReloadPolicy,
-    index: Index,
+    index: Index<C>,
     warmers: Vec<Weak<dyn Warmer>>,
     num_warming_threads: usize,
     doc_store_cache_num_blocks: usize,
 }
 
-impl IndexReaderBuilder {
+impl<C: Codec> IndexReaderBuilder<C> {
     #[must_use]
-    pub(crate) fn new(index: Index) -> IndexReaderBuilder {
+    pub(crate) fn new(index: Index<C>) -> IndexReaderBuilder<C> {
         IndexReaderBuilder {
             reload_policy: ReloadPolicy::OnCommitWithDelay,
             index,
@@ -63,7 +64,7 @@ impl IndexReaderBuilder {
     /// Building the reader is a non-trivial operation that requires
     /// to open different segment readers. It may take hundreds of milliseconds
     /// of time and it may return an error.
-    pub fn try_into(self) -> crate::Result<IndexReader> {
+    pub fn try_into(self) -> crate::Result<IndexReader<C>> {
         let searcher_generation_inventory = Inventory::default();
         let warming_state = WarmingState::new(
             self.num_warming_threads,
@@ -106,7 +107,7 @@ impl IndexReaderBuilder {
     ///
     /// See [`ReloadPolicy`] for more details.
     #[must_use]
-    pub fn reload_policy(mut self, reload_policy: ReloadPolicy) -> IndexReaderBuilder {
+    pub fn reload_policy(mut self, reload_policy: ReloadPolicy) -> IndexReaderBuilder<C> {
         self.reload_policy = reload_policy;
         self
     }
@@ -118,14 +119,14 @@ impl IndexReaderBuilder {
     pub fn doc_store_cache_num_blocks(
         mut self,
         doc_store_cache_num_blocks: usize,
-    ) -> IndexReaderBuilder {
+    ) -> IndexReaderBuilder<C> {
         self.doc_store_cache_num_blocks = doc_store_cache_num_blocks;
         self
     }
 
     /// Set the [`Warmer`]s that are invoked when reloading searchable segments.
     #[must_use]
-    pub fn warmers(mut self, warmers: Vec<Weak<dyn Warmer>>) -> IndexReaderBuilder {
+    pub fn warmers(mut self, warmers: Vec<Weak<dyn Warmer>>) -> IndexReaderBuilder<C> {
         self.warmers = warmers;
         self
     }
@@ -135,33 +136,33 @@ impl IndexReaderBuilder {
     /// This allows parallelizing warming work when there are multiple [`Warmer`] registered with
     /// the [`IndexReader`].
     #[must_use]
-    pub fn num_warming_threads(mut self, num_warming_threads: usize) -> IndexReaderBuilder {
+    pub fn num_warming_threads(mut self, num_warming_threads: usize) -> IndexReaderBuilder<C> {
         self.num_warming_threads = num_warming_threads;
         self
     }
 }
 
-impl TryInto<IndexReader> for IndexReaderBuilder {
+impl<C: Codec> TryInto<IndexReader<C>> for IndexReaderBuilder<C> {
     type Error = crate::TantivyError;
 
-    fn try_into(self) -> crate::Result<IndexReader> {
+    fn try_into(self) -> crate::Result<IndexReader<C>> {
         IndexReaderBuilder::try_into(self)
     }
 }
 
-struct InnerIndexReader {
+struct InnerIndexReader<C: Codec> {
     doc_store_cache_num_blocks: usize,
-    index: Index,
+    index: Index<C>,
     warming_state: WarmingState,
     searcher: arc_swap::ArcSwap<SearcherInner>,
     searcher_generation_counter: Arc<AtomicU64>,
     searcher_generation_inventory: Inventory<SearcherGeneration>,
 }
 
-impl InnerIndexReader {
+impl<C: Codec> InnerIndexReader<C> {
     fn new(
         doc_store_cache_num_blocks: usize,
-        index: Index,
+        index: Index<C>,
         warming_state: WarmingState,
         // The searcher_generation_inventory is not used as source, but as target to track the
         // loaded segments.
@@ -189,7 +190,7 @@ impl InnerIndexReader {
     ///
     /// This function acquires a lock to prevent GC from removing files
     /// as we are opening our index.
-    fn open_segment_readers(index: &Index) -> crate::Result<Vec<SegmentReader>> {
+    fn open_segment_readers(index: &Index<C>) -> crate::Result<Vec<SegmentReader>> {
         // Prevents segment files from getting deleted while we are in the process of opening them
         let _meta_lock = index.directory().acquire_lock(&META_LOCK)?;
         let searchable_segments = index.searchable_segments()?;
@@ -212,7 +213,7 @@ impl InnerIndexReader {
     }
 
     fn create_searcher(
-        index: &Index,
+        index: &Index<C>,
         doc_store_cache_num_blocks: usize,
         warming_state: &WarmingState,
         searcher_generation_counter: &Arc<AtomicU64>,
@@ -226,9 +227,10 @@ impl InnerIndexReader {
         );
 
         let schema = index.schema();
+        // SearcherInner uses Index<StandardCodec> since the codec doesn't affect reading
         let searcher = Arc::new(SearcherInner::new(
             schema,
-            index.clone(),
+            index.with_standard_codec(),
             segment_readers,
             searcher_generation,
             doc_store_cache_num_blocks,
@@ -264,14 +266,14 @@ impl InnerIndexReader {
 ///
 /// `IndexReader` just wraps an `Arc`.
 #[derive(Clone)]
-pub struct IndexReader {
-    inner: Arc<InnerIndexReader>,
+pub struct IndexReader<C: Codec = crate::codec::StandardCodec> {
+    inner: Arc<InnerIndexReader<C>>,
     _watch_handle_opt: Option<WatchHandle>,
 }
 
-impl IndexReader {
+impl<C: Codec> IndexReader<C> {
     #[cfg(test)]
-    pub(crate) fn index(&self) -> Index {
+    pub(crate) fn index(&self) -> Index<C> {
         self.inner.index.clone()
     }