Fix chunked_buffer clippy

Still lots of work to do here. Also a lot of copying going on that
should be avoided.

pageserver/src/layered_repository.rs

@@ -1601,7 +1601,7 @@ impl LayeredTimeline {
                     rel,
                     request_lsn
                 );
-                Ok(img.clone())
+                Ok(Bytes::from(img.image().to_vec()))
             } else {
                 // FIXME: this ought to be an error?
                 warn!("Page {} blk {} at {} not found", rel, blknum, request_lsn);
@@ -1612,7 +1612,7 @@ impl LayeredTimeline {
             //
             // If we don't have a base image, then the oldest WAL record better initialize
             // the page
-            if data.page_img.is_none() && !data.records.first().unwrap().1.will_init {
+            if data.page_img.is_none() && !data.records.first().unwrap().1.will_init() {
                 // FIXME: this ought to be an error?
                 warn!(
                     "Base image for page {}/{} at {} not found, but got {} WAL records",
@@ -1632,7 +1632,7 @@ impl LayeredTimeline {
                     rel,
                     blknum,
                     request_lsn,
-                    data.page_img.clone(),
+                    data.page_img.map(|page| Bytes::from(page.image().to_vec())), // FIXME
                     data.records,
                 )?;
 

pageserver/src/layered_repository/blob.rs

@@ -10,10 +10,10 @@ pub struct BlobRange {
     size: usize,
 }
 
-pub fn read_blob(reader: &BoundedReader<&'_ File>, range: &BlobRange) -> Result<Vec<u8>> {
+pub fn read_blob(reader: &BoundedReader<&'_ File>, range: &BlobRange) -> Result<Box<[u8]>> {
     let mut buf = vec![0u8; range.size];
     reader.read_exact_at(&mut buf, range.offset)?;
-    Ok(buf)
+    Ok(buf.into_boxed_slice())
 }
 
 pub struct BlobWriter<W> {

pageserver/src/layered_repository/delta_layer.rs

@@ -39,6 +39,7 @@
 //!
 use crate::layered_repository::blob::BlobWriter;
 use crate::layered_repository::filename::{DeltaFileName, PathOrConf};
+use crate::layered_repository::page_versions::PageVersions;
 use crate::layered_repository::storage_layer::{
     Layer, PageReconstructData, PageReconstructResult, PageVersion, SegmentTag,
 };
@@ -46,6 +47,7 @@ use crate::waldecoder;
 use crate::PageServerConf;
 use crate::{ZTenantId, ZTimelineId};
 use anyhow::{bail, ensure, Result};
+use bytes::Bytes;
 use log::*;
 use serde::{Deserialize, Serialize};
 use zenith_utils::vec_map::VecMap;
@@ -203,7 +205,8 @@ impl Layer for DeltaLayer {
                 .iter()
                 .rev();
             for ((_blknum, pv_lsn), blob_range) in iter {
-                let pv = PageVersion::des(&read_blob(&page_version_reader, blob_range)?)?;
+                let pv_bytes = read_blob(&page_version_reader, blob_range)?;
+                let pv = PageVersion::from_bytes(pv_bytes);
 
                 match pv {
                     PageVersion::Page(img) => {
@@ -213,7 +216,7 @@ impl Layer for DeltaLayer {
                         break;
                     }
                     PageVersion::Wal(rec) => {
-                        let will_init = rec.will_init;
+                        let will_init = rec.will_init();
                         reconstruct_data.records.push((*pv_lsn, rec));
                         if will_init {
                             // This WAL record initializes the page, so no need to go further back
@@ -309,19 +312,20 @@ impl Layer for DeltaLayer {
             let mut desc = String::new();
 
             let buf = read_blob(&chapter, blob_range)?;
-            let pv = PageVersion::des(&buf)?;
+            let pv = PageVersion::from_bytes(buf);
 
             match pv {
-                PageVersion::Page(img) => {
+                PageVersion::Page(page) => {
-                    write!(&mut desc, " img {} bytes", img.len())?;
+                    write!(&mut desc, " img {} bytes", page.image().len())?;
                 }
                 PageVersion::Wal(rec) => {
-                    let wal_desc = waldecoder::describe_wal_record(&rec.rec);
+                    let wal_desc =
+                        waldecoder::describe_wal_record(&Bytes::from(rec.rec().to_vec()));
                     write!(
                         &mut desc,
                         " rec {} bytes will_init: {} {}",
-                        rec.rec.len(),
+                        rec.rec().len(),
-                        rec.will_init,
+                        rec.will_init(),
                         wal_desc
                     )?;
                 }
@@ -350,14 +354,14 @@ impl DeltaLayer {
     }
 
     /// Create a new delta file, using the given page versions and relsizes.
-    /// The page versions are passed by an iterator; the iterator must return
+    /// The page versions are passed in a PageVersions struct. If 'cutoff' is
-    /// page versions in blknum+lsn order.
+    /// given, only page versions with LSN < cutoff are included.
     ///
-    /// This is used to write the in-memory layer to disk. The in-memory layer uses the same
+    /// This is used to write the in-memory layer to disk. The page_versions and
-    /// data structure with two btreemaps as we do, so passing the btreemaps is currently
+    /// relsizes are thus passed in the same format as they are in the in-memory
-    /// expedient.
+    /// layer, as that's expedient.
     #[allow(clippy::too_many_arguments)]
-    pub fn create<'a>(
+    pub fn create(
         conf: &'static PageServerConf,
         timelineid: ZTimelineId,
         tenantid: ZTenantId,
@@ -365,7 +369,8 @@ impl DeltaLayer {
         start_lsn: Lsn,
         end_lsn: Lsn,
         dropped: bool,
-        page_versions: impl Iterator<Item = (u32, Lsn, &'a PageVersion)>,
+        page_versions: &PageVersions,
+        cutoff: Option<Lsn>,
         relsizes: VecMap<Lsn, u32>,
     ) -> Result<DeltaLayer> {
         if seg.rel.is_blocky() {
@@ -399,9 +404,10 @@ impl DeltaLayer {
 
         let mut page_version_writer = BlobWriter::new(book, PAGE_VERSIONS_CHAPTER);
 
-        for (blknum, lsn, page_version) in page_versions {
+        let page_versions_iter = page_versions.ordered_page_version_iter(cutoff);
-            let buf = PageVersion::ser(page_version)?;
+        for (blknum, lsn, token) in page_versions_iter {
-            let blob_range = page_version_writer.write_blob(&buf)?;
+            let blob_range = page_version_writer
+                .write_blob(page_versions.get_page_version_bytes(token).as_slice())?;
 
             inner
                 .page_version_metas

pageserver/src/layered_repository/image_layer.rs

@@ -23,7 +23,7 @@
 //!
 use crate::layered_repository::filename::{ImageFileName, PathOrConf};
 use crate::layered_repository::storage_layer::{
-    Layer, PageReconstructData, PageReconstructResult, SegmentTag,
+    Layer, Page, PageReconstructData, PageReconstructResult, SegmentTag,
 };
 use crate::layered_repository::LayeredTimeline;
 use crate::layered_repository::RELISH_SEG_SIZE;
@@ -177,7 +177,7 @@ impl Layer for ImageLayer {
             }
         };
 
-        reconstruct_data.page_img = Some(Bytes::from(buf));
+        reconstruct_data.page_img = Some(Page::from_bytes(&buf));
         Ok(PageReconstructResult::Complete)
     }
 

pageserver/src/layered_repository/inmemory_layer.rs

@@ -8,7 +8,6 @@ use crate::layered_repository::storage_layer::{
     Layer, PageReconstructData, PageReconstructResult, PageVersion, SegmentTag, RELISH_SEG_SIZE,
 };
 use crate::layered_repository::LayeredTimeline;
-use crate::layered_repository::ZERO_PAGE;
 use crate::layered_repository::{DeltaLayer, ImageLayer};
 use crate::repository::WALRecord;
 use crate::PageServerConf;
@@ -24,6 +23,7 @@ use zenith_utils::vec_map::VecMap;
 use zenith_utils::lsn::Lsn;
 
 use super::page_versions::PageVersions;
+use super::storage_layer::Page;
 
 pub struct InMemoryLayer {
     conf: &'static PageServerConf,
@@ -184,16 +184,17 @@ impl Layer for InMemoryLayer {
                 .get_block_lsn_range(blknum, ..=lsn)
                 .iter()
                 .rev();
-            for (entry_lsn, pv) in iter {
+            for (entry_lsn, token) in iter {
-                match pv {
+                match inner.page_versions.get_page_version(token)? {
-                    PageVersion::Page(img) => {
+                    PageVersion::Page(page) => {
-                        reconstruct_data.page_img = Some(img.clone());
+                        reconstruct_data.page_img = Some(page);
                         need_image = false;
                         break;
                     }
                     PageVersion::Wal(rec) => {
-                        reconstruct_data.records.push((*entry_lsn, rec.clone()));
+                        let will_init = rec.will_init();
-                        if rec.will_init {
+                        reconstruct_data.records.push((*entry_lsn, rec));
+                        if will_init {
                             // This WAL record initializes the page, so no need to go further back
                             need_image = false;
                             break;
@@ -285,8 +286,8 @@ impl Layer for InMemoryLayer {
             println!("segsizes {}: {}", k, v);
         }
 
-        for (blknum, lsn, pv) in inner.page_versions.ordered_page_version_iter(None) {
+        for (blknum, lsn, token) in inner.page_versions.ordered_page_version_iter(None) {
-            let pv_description = match pv {
+            let pv_description = match inner.page_versions.get_page_version(token)? {
                 PageVersion::Page(_img) => "page",
                 PageVersion::Wal(_rec) => "wal",
             };
@@ -361,7 +362,7 @@ impl InMemoryLayer {
 
     /// Remember new page version, as a full page image
     pub fn put_page_image(&self, blknum: u32, lsn: Lsn, img: Bytes) -> u32 {
-        self.put_page_version(blknum, lsn, PageVersion::Page(img))
+        self.put_page_version(blknum, lsn, PageVersion::Page(Page::from_bytes(&img)))
     }
 
     /// Common subroutine of the public put_wal_record() and put_page_image() functions.
@@ -382,8 +383,8 @@ impl InMemoryLayer {
 
         let mut mem_usage = 0;
         mem_usage += match &pv {
-            PageVersion::Page(img) => img.len(),
+            PageVersion::Page(page) => page.image().len(),
-            PageVersion::Wal(rec) => rec.rec.len(),
+            PageVersion::Wal(rec) => rec.rec().len(),
         };
 
         let old = inner.page_versions.append_or_update_last(blknum, lsn, pv);
@@ -425,7 +426,7 @@ impl InMemoryLayer {
                 // subsequent call to initialize the gap page.
                 let gapstart = self.seg.segno * RELISH_SEG_SIZE + oldsize;
                 for gapblknum in gapstart..blknum {
-                    let zeropv = PageVersion::Page(ZERO_PAGE.clone());
+                    let zeropv = PageVersion::Page(Page::zero_page());
                     trace!(
                         "filling gap blk {} with zeros for write of {}",
                         gapblknum,
@@ -610,7 +611,8 @@ impl InMemoryLayer {
                 self.start_lsn,
                 end_lsn_exclusive,
                 true,
-                inner.page_versions.ordered_page_version_iter(None),
+                &inner.page_versions,
+                None,
                 inner.segsizes.clone(),
             )?;
             trace!(
@@ -627,13 +629,9 @@ impl InMemoryLayer {
 
         // Since `end_lsn` is inclusive, subtract 1.
         // We want to make an ImageLayer for the last included LSN,
-        // so the DeltaLayer should exlcude that LSN.
+        // so the DeltaLayer should exclude that LSN.
         let end_lsn_inclusive = Lsn(end_lsn_exclusive.0 - 1);
 
-        let mut page_versions = inner
-            .page_versions
-            .ordered_page_version_iter(Some(end_lsn_inclusive));
-
         let mut delta_layers = Vec::new();
 
         if self.start_lsn != end_lsn_inclusive {
@@ -647,7 +645,8 @@ impl InMemoryLayer {
                 self.start_lsn,
                 end_lsn_inclusive,
                 false,
-                page_versions,
+                &inner.page_versions,
+                Some(end_lsn_inclusive),
                 segsizes,
             )?;
             delta_layers.push(delta_layer);
@@ -658,7 +657,11 @@ impl InMemoryLayer {
                 end_lsn_inclusive
             );
         } else {
-            assert!(page_versions.next().is_none());
+            assert!(inner
+                .page_versions
+                .ordered_page_version_iter(None)
+                .next()
+                .is_none());
         }
 
         drop(inner);

pageserver/src/layered_repository/page_versions.rs

@@ -1,13 +1,23 @@
 use std::{collections::HashMap, ops::RangeBounds, slice};
 
+use anyhow::Result;
+
+use zenith_utils::chunked_buffer::{ChunkToken, ChunkedBuffer};
 use zenith_utils::{lsn::Lsn, vec_map::VecMap};
 
 use super::storage_layer::PageVersion;
 
-const EMPTY_SLICE: &[(Lsn, PageVersion)] = &[];
+const EMPTY_SLICE: &[(Lsn, ChunkToken)] = &[];
 
 #[derive(Debug, Default)]
-pub struct PageVersions(HashMap<u32, VecMap<Lsn, PageVersion>>);
+pub struct PageVersions {
+    map: HashMap<u32, VecMap<Lsn, ChunkToken>>,
+
+    /// The PageVersion structs are stored in a serialized format in this buffer.
+    /// Each serialized PageVersion is preceded by a 'u32' length field.
+    /// The 'map' stores offsets into this buffer.
+    buffer: ChunkedBuffer,
+}
 
 impl PageVersions {
     pub fn append_or_update_last(
@@ -15,14 +25,16 @@ impl PageVersions {
         blknum: u32,
         lsn: Lsn,
         page_version: PageVersion,
-    ) -> Option<PageVersion> {
+    ) -> Option<ChunkToken> {
-        let map = self.0.entry(blknum).or_insert_with(VecMap::default);
+        let token = self.buffer.write(page_version.bytes());
-        map.append_or_update_last(lsn, page_version).unwrap()
+
+        let map = self.map.entry(blknum).or_insert_with(VecMap::default);
+        map.append_or_update_last(lsn, token).unwrap()
     }
 
     /// Get all [`PageVersion`]s in a block
-    pub fn get_block_slice(&self, blknum: u32) -> &[(Lsn, PageVersion)] {
+    fn get_block_slice(&self, blknum: u32) -> &[(Lsn, ChunkToken)] {
-        self.0
+        self.map
             .get(&blknum)
             .map(VecMap::as_slice)
             .unwrap_or(EMPTY_SLICE)
@@ -33,8 +45,8 @@ impl PageVersions {
         &self,
         blknum: u32,
         range: R,
-    ) -> &[(Lsn, PageVersion)] {
+    ) -> &[(Lsn, ChunkToken)] {
-        self.0
+        self.map
             .get(&blknum)
             .map(|vec_map| vec_map.slice_range(range))
             .unwrap_or(EMPTY_SLICE)
@@ -43,7 +55,7 @@ impl PageVersions {
     /// Iterate through [`PageVersion`]s in (block, lsn) order.
     /// If a [`cutoff_lsn`] is set, only show versions with `lsn < cutoff_lsn`
     pub fn ordered_page_version_iter(&self, cutoff_lsn: Option<Lsn>) -> OrderedPageVersionIter<'_> {
-        let mut ordered_blocks: Vec<u32> = self.0.keys().cloned().collect();
+        let mut ordered_blocks: Vec<u32> = self.map.keys().cloned().collect();
         ordered_blocks.sort_unstable();
 
         let slice = ordered_blocks
@@ -59,6 +71,15 @@ impl PageVersions {
             cur_slice_iter: slice.iter(),
         }
     }
+
+    pub fn get_page_version_bytes(&self, token: &ChunkToken) -> Vec<u8> {
+        self.buffer.read(token)
+    }
+
+    pub fn get_page_version(&self, token: &ChunkToken) -> Result<PageVersion> {
+        let buf = self.get_page_version_bytes(token).into_boxed_slice();
+        Ok(PageVersion::from_bytes(buf))
+    }
 }
 
 pub struct OrderedPageVersionIter<'a> {
@@ -69,7 +90,7 @@ pub struct OrderedPageVersionIter<'a> {
 
     cutoff_lsn: Option<Lsn>,
 
-    cur_slice_iter: slice::Iter<'a, (Lsn, PageVersion)>,
+    cur_slice_iter: slice::Iter<'a, (Lsn, ChunkToken)>,
 }
 
 impl OrderedPageVersionIter<'_> {
@@ -83,14 +104,14 @@ impl OrderedPageVersionIter<'_> {
 }
 
 impl<'a> Iterator for OrderedPageVersionIter<'a> {
-    type Item = (u32, Lsn, &'a PageVersion);
+    type Item = (u32, Lsn, &'a ChunkToken);
 
     fn next(&mut self) -> Option<Self::Item> {
         loop {
-            if let Some((lsn, page_version)) = self.cur_slice_iter.next() {
+            if let Some((lsn, token)) = self.cur_slice_iter.next() {
                 if self.is_lsn_before_cutoff(lsn) {
                     let blknum = self.ordered_blocks[self.cur_block_idx];
-                    return Some((blknum, *lsn, page_version));
+                    return Some((blknum, *lsn, token));
                 }
             }
 
@@ -104,7 +125,7 @@ impl<'a> Iterator for OrderedPageVersionIter<'a> {
 
 #[cfg(test)]
 mod tests {
-    use bytes::Bytes;
+    use crate::layered_repository::storage_layer::Page;
 
     use super::*;
 
@@ -114,8 +135,7 @@ mod tests {
         const BLOCKS: u32 = 1000;
         const LSNS: u64 = 50;
 
-        let empty_page = Bytes::from_static(&[0u8; 8192]);
+        let empty_page_version = PageVersion::Page(Page::zero_page());
-        let empty_page_version = PageVersion::Page(empty_page);
 
         for blknum in 0..BLOCKS {
             for lsn in 0..LSNS {

pageserver/src/layered_repository/storage_layer.rs

@@ -3,10 +3,9 @@
 //!
 
 use crate::relish::RelishTag;
-use crate::repository::WALRecord;
+use crate::repository::{WALRecord, WAL_BIT};
 use crate::{ZTenantId, ZTimelineId};
 use anyhow::Result;
-use bytes::Bytes;
 use serde::{Deserialize, Serialize};
 use std::fmt;
 use std::path::PathBuf;
@@ -51,12 +50,52 @@ impl SegmentTag {
 ///
 /// A page version can be stored as a full page image, or as WAL record that needs
 /// to be applied over the previous page version to reconstruct this version.
-#[derive(Debug, Clone, Serialize, Deserialize)]
+#[derive(Debug, Clone)]
 pub enum PageVersion {
-    Page(Bytes),
+    Page(Page),
     Wal(WALRecord),
 }
 
+impl PageVersion {
+    pub fn from_bytes(bytes: Box<[u8]>) -> Self {
+        if bytes[0] & WAL_BIT != 0 {
+            Self::Wal(WALRecord::from_bytes(bytes))
+        } else {
+            Self::Page(Page(bytes))
+        }
+    }
+
+    pub fn bytes(&self) -> &[u8] {
+        match self {
+            Self::Page(page) => page.bytes(),
+            Self::Wal(wal) => wal.bytes(),
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct Page(Box<[u8]>);
+
+impl Page {
+    pub fn zero_page() -> Self {
+        // TODO optimize this
+        Self(vec![0u8; 1 + 8192].into_boxed_slice())
+    }
+    pub fn from_bytes(bytes: &[u8]) -> Self {
+        let mut buf = vec![0u8; 1 + bytes.len()];
+        buf[1..].copy_from_slice(bytes);
+        Self(buf.into_boxed_slice())
+    }
+
+    pub fn image(&self) -> &[u8] {
+        &self.0[1..]
+    }
+
+    pub fn bytes(&self) -> &[u8] {
+        &self.0
+    }
+}
+
 ///
 /// Data needed to reconstruct a page version
 ///
@@ -66,7 +105,7 @@ pub enum PageVersion {
 ///
 pub struct PageReconstructData {
     pub records: Vec<(Lsn, WALRecord)>,
-    pub page_img: Option<Bytes>,
+    pub page_img: Option<Page>,
 }
 
 /// Return value from Layer::get_page_reconstruct_data

pageserver/src/repository.rs

@@ -2,8 +2,8 @@ use crate::relish::*;
 use crate::CheckpointConfig;
 use anyhow::Result;
 use bytes::Bytes;
-use serde::{Deserialize, Serialize};
 use std::collections::HashSet;
+use std::convert::TryInto;
 use std::ops::{AddAssign, Deref};
 use std::sync::Arc;
 use std::time::Duration;
@@ -192,14 +192,45 @@ pub trait TimelineWriter: Deref<Target = dyn Timeline> {
     fn advance_last_record_lsn(&self, lsn: Lsn);
 }
 
-#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[derive(Debug, Clone)]
-pub struct WALRecord {
+pub struct WALRecord(Box<[u8]>);
-    pub will_init: bool,
+
-    pub rec: Bytes,
+pub const WAL_BIT: u8 = 0b1;
+const WILL_INIT_BIT: u8 = 0b10;
+
+impl WALRecord {
+    pub fn new(will_init: bool, main_data_offset: u32, rec: &[u8]) -> Self {
+        // TODO avoid init
+        let mut buf = vec![0u8; 1 + 4 + rec.len()];
+        buf[0] = WAL_BIT | if will_init { WILL_INIT_BIT } else { 0 };
+        let mdo = u32::to_le_bytes(main_data_offset);
+        buf[1..5].copy_from_slice(&mdo);
+        buf[5..].copy_from_slice(rec);
+        Self(buf.into_boxed_slice())
+    }
+
+    pub fn from_bytes(bytes: Box<[u8]>) -> Self {
+        Self(bytes)
+    }
+
+    pub fn will_init(&self) -> bool {
+        self.0[0] & WILL_INIT_BIT != 0
+    }
+
     // Remember the offset of main_data in rec,
     // so that we don't have to parse the record again.
     // If record has no main_data, this offset equals rec.len().
-    pub main_data_offset: u32,
+    pub fn main_data_offset(&self) -> u32 {
+        u32::from_le_bytes(self.0[1..5].try_into().unwrap())
+    }
+
+    pub fn rec(&self) -> &[u8] {
+        &self.0[5..]
+    }
+
+    pub fn bytes(&self) -> &[u8] {
+        &self.0[..]
+    }
 }
 
 #[cfg(test)]

pageserver/src/restore_local_repo.rs

@@ -427,11 +427,11 @@ pub fn save_decoded_record(
             forknum: blk.forknum as u8,
         });
 
-        let rec = WALRecord {
+        let rec = WALRecord::new(
-            will_init: blk.will_init || blk.apply_image,
+            blk.will_init || blk.apply_image,
-            rec: recdata.clone(),
+            decoded.main_data_offset as u32,
-            main_data_offset: decoded.main_data_offset as u32,
+            &recdata[..],
-        };
+        );
 
         timeline.put_wal_record(lsn, tag, blk.blkno, rec)?;
     }
@@ -770,11 +770,7 @@ fn save_xact_record(
 
     let segno = pageno / pg_constants::SLRU_PAGES_PER_SEGMENT;
     let rpageno = pageno % pg_constants::SLRU_PAGES_PER_SEGMENT;
-    let rec = WALRecord {
+    let rec = WALRecord::new(false, decoded.main_data_offset as u32, &decoded.record[..]);
-        will_init: false,
-        rec: decoded.record.clone(),
-        main_data_offset: decoded.main_data_offset as u32,
-    };
     timeline.put_wal_record(
         lsn,
         RelishTag::Slru {
@@ -886,11 +882,7 @@ fn save_multixact_create_record(
     xlrec: &XlMultiXactCreate,
     decoded: &DecodedWALRecord,
 ) -> Result<()> {
-    let rec = WALRecord {
+    let rec = WALRecord::new(false, decoded.main_data_offset as u32, &decoded.record[..]);
-        will_init: false,
-        rec: decoded.record.clone(),
-        main_data_offset: decoded.main_data_offset as u32,
-    };
     let pageno = xlrec.mid / pg_constants::MULTIXACT_OFFSETS_PER_PAGE as u32;
     let segno = pageno / pg_constants::SLRU_PAGES_PER_SEGMENT;
     let rpageno = pageno % pg_constants::SLRU_PAGES_PER_SEGMENT;

pageserver/src/walredo.rs

@@ -317,7 +317,7 @@ impl PostgresRedoManager {
         }
         // Apply all collected WAL records
         for (_lsn, record) in records {
-            let mut buf = record.rec.clone();
+            let mut buf = Bytes::from(record.rec().to_vec());
 
             WAL_REDO_RECORD_COUNTER.inc();
 
@@ -328,7 +328,7 @@ impl PostgresRedoManager {
             //move to main data
             // TODO probably, we should store some records in our special format
             // to avoid this weird parsing on replay
-            let skip = (record.main_data_offset - pg_constants::SIZEOF_XLOGRECORD) as usize;
+            let skip = (record.main_data_offset() - pg_constants::SIZEOF_XLOGRECORD) as usize;
             if buf.remaining() > skip {
                 buf.advance(skip);
             }
@@ -574,7 +574,7 @@ impl PostgresRedoProcess {
             build_push_page_msg(tag, &img, &mut writebuf);
         }
         for (lsn, rec) in records.iter() {
-            build_apply_record_msg(*lsn, &rec.rec, &mut writebuf);
+            build_apply_record_msg(*lsn, rec.rec(), &mut writebuf);
         }
         build_get_page_msg(tag, &mut writebuf);
         WAL_REDO_RECORD_COUNTER.inc_by(records.len() as u64);

zenith_utils/src/chunked_buffer.rs

@@ -0,0 +1,173 @@
+use std::convert::TryInto;
+
+const CHUNK_SIZE: usize = 1024;
+
+///
+/// ChunkedBuffer is an expandable byte buffer. You can append to the end of it, and you
+/// can read at any byte position. The advantage over a plain Vec<u8> is that the
+/// buffer consists of smaller chunks, so that a big buffer doesn't require one huge
+/// allocation, and expanding doesn't require copying all the data.
+///
+#[derive(Debug, Default)]
+pub struct ChunkedBuffer {
+    // Clippy considers it unnecessary to have Box here, since the vector is stored
+    // on the heap anyway. But we have our reasons for that: we want each chunk to
+    // be allocated separately, so that we don't require one huge allocation, and so
+    // that expanding the array doesn't require copying all of the data. (Clippy
+    // knows about that and doesn't complain if the array is large enough, 4096
+    // bytes is the default threshold. Our chunk size is smaller than that so that
+    // heuristic doesn't save us.)
+    #[allow(clippy::vec_box)]
+    chunks: Vec<Box<[u8; CHUNK_SIZE]>>,
+
+    length: usize,
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub struct ChunkToken {
+    start: usize,
+    length: usize,
+}
+
+impl ChunkedBuffer {
+    pub fn read(&self, token: &ChunkToken) -> Vec<u8> {
+        let mut buf = Vec::with_capacity(token.length);
+
+        let chunk_idx = token.start / CHUNK_SIZE;
+        let mut chunk_iter = self.chunks[chunk_idx..].iter();
+        let mut bytes_remaining = token.length;
+        if bytes_remaining > 0 {
+            let start_offset = token.start % CHUNK_SIZE;
+            let chunk_bytes = &chunk_iter.next().unwrap()[start_offset..];
+            let bytes = &chunk_bytes[..chunk_bytes.len().min(bytes_remaining)];
+            buf.extend_from_slice(bytes);
+            bytes_remaining -= bytes.len();
+        }
+
+        while bytes_remaining > 0 {
+            let chunk_bytes = chunk_iter.next().unwrap();
+            let bytes = &chunk_bytes[..chunk_bytes.len().min(bytes_remaining)];
+            buf.extend_from_slice(bytes);
+            bytes_remaining -= bytes.len();
+        }
+
+        debug_assert_eq!(buf.len(), token.length);
+        buf
+    }
+
+    pub fn write(&mut self, mut buf: &[u8]) -> ChunkToken {
+        let token = ChunkToken {
+            start: self.length,
+            length: buf.len(),
+        };
+
+        while !buf.is_empty() {
+            let chunk_idx = self.length / CHUNK_SIZE;
+            let chunk = match self.chunks.get_mut(chunk_idx) {
+                Some(chunk) => chunk,
+                None => {
+                    debug_assert_eq!(self.length % CHUNK_SIZE, 0);
+                    debug_assert_eq!(chunk_idx, self.chunks.len());
+                    self.chunks.push(heap_alloc_chunk());
+                    self.chunks.last_mut().unwrap()
+                }
+            };
+
+            let offset = self.length % CHUNK_SIZE;
+            let length = buf.len().min(CHUNK_SIZE - offset);
+
+            chunk[offset..][..length].copy_from_slice(&buf[..length]);
+            buf = &buf[length..];
+            self.length += length;
+        }
+
+        token
+    }
+}
+
+fn heap_alloc_chunk() -> Box<[u8; CHUNK_SIZE]> {
+    vec![0u8; CHUNK_SIZE].into_boxed_slice().try_into().unwrap()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{ChunkToken, ChunkedBuffer, CHUNK_SIZE};
+
+    fn gen_bytes(len: usize) -> Vec<u8> {
+        let mut buf = vec![0u8; len];
+        for (idx, val) in buf.iter_mut().enumerate() {
+            *val = idx as u8;
+        }
+
+        buf
+    }
+
+    #[test]
+    fn one_item() {
+        fn test(data: &[u8]) {
+            let mut chunked_buffer = ChunkedBuffer::default();
+            let token = chunked_buffer.write(data);
+            assert_eq!(
+                ChunkToken {
+                    start: 0,
+                    length: data.len(),
+                },
+                token
+            );
+
+            let buf = chunked_buffer.read(&token);
+            assert_eq!(data, buf.as_slice());
+        }
+
+        test(b"");
+        test(b"a");
+        test(b"abc");
+
+        test(&gen_bytes(CHUNK_SIZE - 1));
+        test(&gen_bytes(CHUNK_SIZE));
+        test(&gen_bytes(CHUNK_SIZE + 1));
+
+        test(&gen_bytes(2 * CHUNK_SIZE - 1));
+        test(&gen_bytes(2 * CHUNK_SIZE));
+        test(&gen_bytes(2 * CHUNK_SIZE + 1));
+    }
+
+    #[test]
+    fn many_items() {
+        let mut chunked_buffer = ChunkedBuffer::default();
+        let mut start = 0;
+        let mut expected = Vec::new();
+
+        let mut test = |data: &[u8]| {
+            let token = chunked_buffer.write(data);
+            assert_eq!(
+                ChunkToken {
+                    start,
+                    length: data.len(),
+                },
+                token
+            );
+
+            expected.push((token, data.to_vec()));
+
+            for (token, expected_data) in &expected {
+                let buf = chunked_buffer.read(token);
+                assert_eq!(expected_data, buf.as_slice());
+            }
+
+            start += data.len();
+        };
+
+        test(b"abc");
+        test(b"");
+        test(b"a");
+
+        test(&gen_bytes(CHUNK_SIZE - 1));
+        test(&gen_bytes(CHUNK_SIZE));
+        test(&gen_bytes(CHUNK_SIZE + 1));
+
+        test(&gen_bytes(2 * CHUNK_SIZE - 1));
+        test(&gen_bytes(2 * CHUNK_SIZE));
+        test(&gen_bytes(2 * CHUNK_SIZE + 1));
+    }
+}

zenith_utils/src/lib.rs

@@ -11,6 +11,9 @@ pub mod seqwait;
 /// append only ordered map implemented with a Vec
 pub mod vec_map;
 
+/// expandable byte buffer consisting of fixed-size chunks
+pub mod chunked_buffer;
+
 // Async version of SeqWait. Currently unused.
 // pub mod seqwait_async;