tantivy/sstable/src/lib.rs

use std::io::{self, Write};
use std::ops::Range;
use std::usize;

use merge::ValueMerger;

mod delta;
mod dictionary;
pub mod merge;
mod streamer;
pub mod value;

mod sstable_index;
pub use sstable_index::{BlockAddr, SSTableIndex, SSTableIndexBuilder};
pub(crate) mod vint;
pub use dictionary::Dictionary;
pub use streamer::{Streamer, StreamerBuilder};

mod block_reader;
pub use self::block_reader::BlockReader;
pub use self::delta::{DeltaReader, DeltaWriter};
pub use self::merge::VoidMerge;
use self::value::{U64MonotonicValueReader, U64MonotonicValueWriter, ValueReader, ValueWriter};
use crate::value::{RangeValueReader, RangeValueWriter};

pub type TermOrdinal = u64;

const DEFAULT_KEY_CAPACITY: usize = 50;

/// Given two byte string returns the length of
/// the longest common prefix.
fn common_prefix_len(left: &[u8], right: &[u8]) -> usize {
    left.iter()
        .cloned()
        .zip(right.iter().cloned())
        .take_while(|(left, right)| left == right)
        .count()
}

#[derive(Debug, Copy, Clone)]
pub struct SSTableDataCorruption;

/// SSTable makes it possible to read and write
/// sstables with typed values.
pub trait SSTable: Sized {
    type Value: Clone;
    type ValueReader: ValueReader<Value = Self::Value>;
    type ValueWriter: ValueWriter<Value = Self::Value>;

    fn delta_writer<W: io::Write>(write: W) -> DeltaWriter<W, Self::ValueWriter> {
        DeltaWriter::new(write)
    }

    fn writer<W: io::Write>(wrt: W) -> Writer<W, Self::ValueWriter> {
        Writer::new(wrt)
    }

    fn delta_reader<'a, R: io::Read + 'a>(reader: R) -> DeltaReader<'a, Self::ValueReader> {
        DeltaReader::new(reader)
    }

    fn reader<'a, R: io::Read + 'a>(reader: R) -> Reader<'a, Self::ValueReader> {
        Reader {
            key: Vec::with_capacity(DEFAULT_KEY_CAPACITY),
            delta_reader: Self::delta_reader(reader),
        }
    }

    /// Returns an empty static reader.
    fn create_empty_reader() -> Reader<'static, Self::ValueReader> {
        Self::reader(&b""[..])
    }

    fn merge<R: io::Read, W: io::Write, M: ValueMerger<Self::Value>>(
        io_readers: Vec<R>,
        w: W,
        merger: M,
    ) -> io::Result<()> {
        let readers: Vec<_> = io_readers.into_iter().map(Self::reader).collect();
        let writer = Self::writer(w);
        merge::merge_sstable::<Self, _, _>(readers, writer, merger)
    }
}

#[allow(dead_code)]
pub struct VoidSSTable;

impl SSTable for VoidSSTable {
    type Value = ();
    type ValueReader = value::VoidValueReader;
    type ValueWriter = value::VoidValueWriter;
}

/// SSTable associated keys to u64
/// sorted in order.
///
/// In other words, two keys `k1` and `k2`
/// such that `k1` <= `k2`, are required to observe
/// `range_sstable[k1] <= range_sstable[k2]`.
#[allow(dead_code)]
pub struct MonotonicU64SSTable;

impl SSTable for MonotonicU64SSTable {
    type Value = u64;

    type ValueReader = U64MonotonicValueReader;

    type ValueWriter = U64MonotonicValueWriter;
}

/// SSTable associating keys to ranges.
/// The range are required to partition the
/// space.
///
/// In other words, two consecutive keys `k1` and `k2`
/// are required to observe
/// `range_sstable[k1].end == range_sstable[k2].start`.
///
/// The first range is not required to start at `0`.
pub struct RangeSSTable;

impl SSTable for RangeSSTable {
    type Value = Range<u64>;

    type ValueReader = RangeValueReader;

    type ValueWriter = RangeValueWriter;
}

/// SSTable reader.
pub struct Reader<'a, TValueReader> {
    key: Vec<u8>,
    delta_reader: DeltaReader<'a, TValueReader>,
}

impl<'a, TValueReader> Reader<'a, TValueReader>
where TValueReader: ValueReader
{
    pub fn advance(&mut self) -> io::Result<bool> {
        if !self.delta_reader.advance()? {
            return Ok(false);
        }
        let common_prefix_len = self.delta_reader.common_prefix_len();
        let suffix = self.delta_reader.suffix();
        let new_len = self.delta_reader.common_prefix_len() + suffix.len();
        self.key.resize(new_len, 0u8);
        self.key[common_prefix_len..].copy_from_slice(suffix);
        Ok(true)
    }

    #[inline(always)]
    pub fn key(&self) -> &[u8] {
        &self.key
    }

    #[inline(always)]
    pub fn value(&self) -> &TValueReader::Value {
        self.delta_reader.value()
    }
}

impl<'a, TValueReader> AsRef<[u8]> for Reader<'a, TValueReader> {
    #[inline(always)]
    fn as_ref(&self) -> &[u8] {
        &self.key
    }
}

pub struct Writer<W, TValueWriter>
where W: io::Write
{
    previous_key: Vec<u8>,
    index_builder: SSTableIndexBuilder,
    delta_writer: DeltaWriter<W, TValueWriter>,
    num_terms: u64,
    first_ordinal_of_the_block: u64,
}

impl<W, TValueWriter> Writer<W, TValueWriter>
where
    W: io::Write,
    TValueWriter: value::ValueWriter,
{
    /// Use `Self::new`. This method only exists to match its
    /// equivalent in fst.
    /// TODO remove this function. (See Issue #1727)
    #[doc(hidden)]
    pub fn create(wrt: W) -> io::Result<Self> {
        Ok(Self::new(wrt))
    }

    /// Creates a new `TermDictionaryBuilder`.
    pub fn new(wrt: W) -> Self {
        Writer {
            previous_key: Vec::with_capacity(DEFAULT_KEY_CAPACITY),
            num_terms: 0u64,
            index_builder: SSTableIndexBuilder::default(),
            delta_writer: DeltaWriter::new(wrt),
            first_ordinal_of_the_block: 0u64,
        }
    }

    /// Returns the last inserted key.
    /// If no key has been inserted yet, or the block was just
    /// flushed, this function returns "".
    #[inline(always)]
    pub(crate) fn last_inserted_key(&self) -> &[u8] {
        &self.previous_key[..]
    }

    /// Inserts a `(key, value)` pair in the term dictionary.
    /// Keys have to be inserted in order.
    ///
    /// # Panics
    ///
    /// Will panics if keys are inserted in an invalid order.
    #[inline]
    pub fn insert<K: AsRef<[u8]>>(
        &mut self,
        key: K,
        value: &TValueWriter::Value,
    ) -> io::Result<()> {
        self.insert_key(key.as_ref())?;
        self.insert_value(value)?;
        Ok(())
    }

    /// # Warning
    ///
    /// Horribly dangerous internal API. See `.insert(...)`.
    #[doc(hidden)]
    #[inline]
    pub fn insert_key(&mut self, key: &[u8]) -> io::Result<()> {
        // If this is the first key in the block, we use it to
        // shorten the last term in the last block.
        if self.first_ordinal_of_the_block == self.num_terms {
            self.index_builder
                .shorten_last_block_key_given_next_key(key);
        }
        let keep_len = common_prefix_len(&self.previous_key, key);
        let add_len = key.len() - keep_len;
        let increasing_keys = add_len > 0 && (self.previous_key.len() == keep_len)
            || self.previous_key.is_empty()
            || self.previous_key[keep_len] < key[keep_len];
        assert!(
            increasing_keys,
            "Keys should be increasing. ({:?} > {:?})",
            self.previous_key, key
        );
        self.previous_key.resize(key.len(), 0u8);
        self.previous_key[keep_len..].copy_from_slice(&key[keep_len..]);
        self.delta_writer.write_suffix(keep_len, &key[keep_len..]);
        Ok(())
    }

    /// # Warning
    ///
    /// Horribly dangerous internal API. See `.insert(...)`.
    #[doc(hidden)]
    #[inline]
    pub fn insert_value(&mut self, value: &TValueWriter::Value) -> io::Result<()> {
        self.delta_writer.write_value(value);
        self.num_terms += 1u64;
        self.flush_block_if_required()
    }

    pub fn flush_block_if_required(&mut self) -> io::Result<()> {
        if let Some(byte_range) = self.delta_writer.flush_block_if_required()? {
            self.index_builder.add_block(
                &self.previous_key[..],
                byte_range,
                self.first_ordinal_of_the_block,
            );
            self.first_ordinal_of_the_block = self.num_terms;
            self.previous_key.clear();
        }
        Ok(())
    }

    pub fn finish(mut self) -> io::Result<W> {
        if let Some(byte_range) = self.delta_writer.flush_block()? {
            self.index_builder.add_block(
                &self.previous_key[..],
                byte_range,
                self.first_ordinal_of_the_block,
            );
            self.first_ordinal_of_the_block = self.num_terms;
        }
        let mut wrt = self.delta_writer.finish();
        wrt.write_all(&0u32.to_le_bytes())?;

        let offset = wrt.written_bytes();

        self.index_builder.serialize(&mut wrt)?;
        wrt.write_all(&offset.to_le_bytes())?;
        wrt.write_all(&self.num_terms.to_le_bytes())?;
        let wrt = wrt.finish();
        Ok(wrt.into_inner()?)
    }
}

impl<TValueWriter> Writer<Vec<u8>, TValueWriter>
where TValueWriter: value::ValueWriter
{
    #[inline]
    pub fn insert_cannot_fail<K: AsRef<[u8]>>(&mut self, key: K, value: &TValueWriter::Value) {
        self.insert(key, value)
            .expect("SSTable over a Vec should never fail");
    }
}

#[cfg(test)]
mod test {
    use std::io;
    use std::ops::Bound;

    use super::{common_prefix_len, MonotonicU64SSTable, SSTable, VoidMerge, VoidSSTable};

    fn aux_test_common_prefix_len(left: &str, right: &str, expect_len: usize) {
        assert_eq!(
            common_prefix_len(left.as_bytes(), right.as_bytes()),
            expect_len
        );
        assert_eq!(
            common_prefix_len(right.as_bytes(), left.as_bytes()),
            expect_len
        );
    }

    #[test]
    fn test_common_prefix_len() {
        aux_test_common_prefix_len("a", "ab", 1);
        aux_test_common_prefix_len("", "ab", 0);
        aux_test_common_prefix_len("ab", "abc", 2);
        aux_test_common_prefix_len("abde", "abce", 2);
    }

    #[test]
    fn test_long_key_diff() {
        let long_key = (0..1_024).map(|x| (x % 255) as u8).collect::<Vec<_>>();
        let long_key2 = (1..300).map(|x| (x % 255) as u8).collect::<Vec<_>>();
        let mut buffer = vec![];
        {
            let mut sstable_writer = VoidSSTable::writer(&mut buffer);
            assert!(sstable_writer.insert(&long_key[..], &()).is_ok());
            assert!(sstable_writer.insert(&[0, 3, 4], &()).is_ok());
            assert!(sstable_writer.insert(&long_key2[..], &()).is_ok());
            assert!(sstable_writer.finish().is_ok());
        }
        let mut sstable_reader = VoidSSTable::reader(&buffer[..]);
        assert!(sstable_reader.advance().unwrap());
        assert_eq!(sstable_reader.key(), &long_key[..]);
        assert!(sstable_reader.advance().unwrap());
        assert_eq!(sstable_reader.key(), &[0, 3, 4]);
        assert!(sstable_reader.advance().unwrap());
        assert_eq!(sstable_reader.key(), &long_key2[..]);
        assert!(!sstable_reader.advance().unwrap());
    }

    #[test]
    fn test_simple_sstable() {
        let mut buffer = vec![];
        {
            let mut sstable_writer = VoidSSTable::writer(&mut buffer);
            assert!(sstable_writer.insert(&[17u8], &()).is_ok());
            assert!(sstable_writer.insert(&[17u8, 18u8, 19u8], &()).is_ok());
            assert!(sstable_writer.insert(&[17u8, 20u8], &()).is_ok());
            assert!(sstable_writer.finish().is_ok());
        }
        assert_eq!(
            &buffer,
            &[
                // block len
                7u8, 0u8, 0u8, 0u8, // keep 0 push 1 |  ""
                16u8, 17u8, // keep 1 push 2 | 18 19
                33u8, 18u8, 19u8, // keep 1 push 1 | 20
                17u8, 20u8, 0u8, 0u8, 0u8, 0u8, // no more blocks
                // index
                161, 102, 98, 108, 111, 99, 107, 115, 129, 162, 115, 108, 97, 115, 116, 95, 107,
                101, 121, 95, 111, 114, 95, 103, 114, 101, 97, 116, 101, 114, 130, 17, 20, 106, 98,
                108, 111, 99, 107, 95, 97, 100, 100, 114, 162, 106, 98, 121, 116, 101, 95, 114, 97,
                110, 103, 101, 162, 101, 115, 116, 97, 114, 116, 0, 99, 101, 110, 100, 11, 109,
                102, 105, 114, 115, 116, 95, 111, 114, 100, 105, 110, 97, 108, 0, 15, 0, 0, 0, 0,
                0, 0, 0, // offset for the index
                3u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8 // num terms
            ]
        );
        let mut sstable_reader = VoidSSTable::reader(&buffer[..]);
        assert!(sstable_reader.advance().unwrap());
        assert_eq!(sstable_reader.key(), &[17u8]);
        assert!(sstable_reader.advance().unwrap());
        assert_eq!(sstable_reader.key(), &[17u8, 18u8, 19u8]);
        assert!(sstable_reader.advance().unwrap());
        assert_eq!(sstable_reader.key(), &[17u8, 20u8]);
        assert!(!sstable_reader.advance().unwrap());
    }

    #[test]
    #[should_panic]
    fn test_simple_sstable_non_increasing_key() {
        let mut buffer = vec![];
        let mut sstable_writer = VoidSSTable::writer(&mut buffer);
        assert!(sstable_writer.insert(&[17u8], &()).is_ok());
        assert!(sstable_writer.insert(&[16u8], &()).is_ok());
    }

    #[test]
    fn test_merge_abcd_abe() {
        let mut buffer = Vec::new();
        {
            let mut writer = VoidSSTable::writer(&mut buffer);
            writer.insert(b"abcd", &()).unwrap();
            writer.insert(b"abe", &()).unwrap();
            writer.finish().unwrap();
        }
        let mut output = Vec::new();
        assert!(VoidSSTable::merge(vec![&buffer[..], &buffer[..]], &mut output, VoidMerge).is_ok());
        assert_eq!(&output[..], &buffer[..]);
    }

    #[test]
    fn test_sstable() {
        let mut buffer = Vec::new();
        {
            let mut writer = VoidSSTable::writer(&mut buffer);
            assert_eq!(writer.last_inserted_key(), b"");
            writer.insert(b"abcd", &()).unwrap();
            assert_eq!(writer.last_inserted_key(), b"abcd");
            writer.insert(b"abe", &()).unwrap();
            assert_eq!(writer.last_inserted_key(), b"abe");
            writer.finish().unwrap();
        }
        let mut output = Vec::new();
        assert!(VoidSSTable::merge(vec![&buffer[..], &buffer[..]], &mut output, VoidMerge).is_ok());
        assert_eq!(&output[..], &buffer[..]);
    }

    #[test]
    fn test_sstable_u64() -> io::Result<()> {
        let mut buffer = Vec::new();
        let mut writer = MonotonicU64SSTable::writer(&mut buffer);
        writer.insert(b"abcd", &1u64)?;
        writer.insert(b"abe", &4u64)?;
        writer.insert(b"gogo", &4324234234234234u64)?;
        writer.finish()?;
        let mut reader = MonotonicU64SSTable::reader(&buffer[..]);
        assert!(reader.advance()?);
        assert_eq!(reader.key(), b"abcd");
        assert_eq!(reader.value(), &1u64);
        assert!(reader.advance()?);
        assert_eq!(reader.key(), b"abe");
        assert_eq!(reader.value(), &4u64);
        assert!(reader.advance()?);
        assert_eq!(reader.key(), b"gogo");
        assert_eq!(reader.value(), &4324234234234234u64);
        assert!(!reader.advance()?);
        Ok(())
    }

    #[test]
    fn test_sstable_empty() {
        let mut sstable_range_empty = crate::RangeSSTable::create_empty_reader();
        assert!(!sstable_range_empty.advance().unwrap());
    }

    use common::file_slice::FileSlice;
    use proptest::prelude::*;

    use crate::Dictionary;

    fn bound_strategy() -> impl Strategy<Value = Bound<String>> {
        prop_oneof![
            Just(Bound::<String>::Unbounded),
            "[a-d]*".prop_map(|key| Bound::Included(key)),
            "[a-d]*".prop_map(|key| Bound::Excluded(key)),
        ]
    }

    fn extract_key(bound: Bound<&String>) -> Option<&str> {
        match bound.as_ref() {
            Bound::Included(key) => Some(key.as_str()),
            Bound::Excluded(key) => Some(key.as_str()),
            Bound::Unbounded => None,
        }
    }

    fn bounds_strategy() -> impl Strategy<Value = (Bound<String>, Bound<String>)> {
        (bound_strategy(), bound_strategy()).prop_filter(
            "Lower bound <= Upper bound",
            |(left, right)| match (extract_key(left.as_ref()), extract_key(right.as_ref())) {
                (None, _) => true,
                (_, None) => true,
                (left, right) => left <= right,
            },
        )
    }

    proptest! {
        #[test]
        fn test_prop_test_ranges(words in prop::collection::btree_set("[a-d]*", 1..100),
            (lower_bound, upper_bound) in bounds_strategy(),
        ) {
            // TODO tweak block size.
            let mut builder = Dictionary::<VoidSSTable>::builder(Vec::new()).unwrap();
            for word in &words {
                builder.insert(word.as_bytes(), &()).unwrap();
            }
            let buffer: Vec<u8> = builder.finish().unwrap();
            let dictionary: Dictionary<VoidSSTable> = Dictionary::open(FileSlice::from(buffer)).unwrap();
            let mut range_builder = dictionary.range();
            range_builder = match lower_bound.as_ref() {
                Bound::Included(key) => range_builder.ge(key.as_bytes()),
                Bound::Excluded(key) => range_builder.gt(key.as_bytes()),
                Bound::Unbounded => range_builder,
            };
            range_builder = match upper_bound.as_ref() {
                Bound::Included(key) => range_builder.le(key.as_bytes()),
                Bound::Excluded(key) => range_builder.lt(key.as_bytes()),
                Bound::Unbounded => range_builder,
            };
            let mut stream = range_builder.into_stream().unwrap();
            let mut btree_set_range = words.range((lower_bound, upper_bound));
            while stream.advance() {
                let val = btree_set_range.next().unwrap();
                assert_eq!(val.as_bytes(), stream.key());
            }
            assert!(btree_set_range.next().is_none());
        }
    }
}