From f0030ae003a2b0e10ce1267f918572fba07a4f66 Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Tue, 3 Aug 2021 13:59:51 +0300
Subject: [PATCH] Handle SLRU ZERO records directly by storing an all-zeros
 page image.

It's simpler than storing the original WAL record.
---
 pageserver/src/restore_local_repo.rs |  6 ++++--
 pageserver/src/walredo.rs            | 17 +++--------------
 2 files changed, 7 insertions(+), 16 deletions(-)

diff --git a/pageserver/src/restore_local_repo.rs b/pageserver/src/restore_local_repo.rs
index cf50af23d4..140172272a 100644
--- a/pageserver/src/restore_local_repo.rs
+++ b/pageserver/src/restore_local_repo.rs
@@ -25,6 +25,8 @@ use zenith_utils::lsn::Lsn;
 const MAX_MBR_BLKNO: u32 =
     pg_constants::MAX_MULTIXACT_ID / pg_constants::MULTIXACT_MEMBERS_PER_PAGE as u32;
 
+const ZERO_PAGE: Bytes = Bytes::from_static(&[0u8; 8192]);
+
 ///
 /// Import all relation data pages from local disk into the repository.
 ///
@@ -415,7 +417,7 @@ pub fn save_decoded_record(
                 rec: recdata.clone(),
                 main_data_offset: decoded.main_data_offset as u32,
             };
-            timeline.put_wal_record(tag, rec)?;
+            timeline.put_page_image(tag, lsn, ZERO_PAGE, false)?;
         } else {
             assert!(info == pg_constants::CLOG_TRUNCATE);
             checkpoint.oldestXid = buf.get_u32_le();
@@ -477,7 +479,7 @@ pub fn save_decoded_record(
             } else {
                 ObjectTag::MultiXactMembers(SlruBufferTag { blknum })
             };
-            timeline.put_wal_record(tag, rec)?;
+            timeline.put_page_image(tag, lsn, ZERO_PAGE, false)?;
         } else if info == pg_constants::XLOG_MULTIXACT_CREATE_ID {
             let xlrec = XlMultiXactCreate::decode(&mut buf);
             save_multixact_create_record(checkpoint, timeline, lsn, &xlrec, decoded)?;
diff --git a/pageserver/src/walredo.rs b/pageserver/src/walredo.rs
index 102c8eb347..4a2820aeba 100644
--- a/pageserver/src/walredo.rs
+++ b/pageserver/src/walredo.rs
@@ -314,13 +314,7 @@ impl PostgresRedoManagerInternal {
                     buf.advance(skip);
                 }
 
-                if xlogrec.xl_rmid == pg_constants::RM_CLOG_ID {
-                    let info = xlogrec.xl_info & !pg_constants::XLR_INFO_MASK;
-                    if info == pg_constants::CLOG_ZEROPAGE {
-                        // The only operation we need to implement is CLOG_ZEROPAGE
-                        page.copy_from_slice(&ZERO_PAGE);
-                    }
-                } else if xlogrec.xl_rmid == pg_constants::RM_XACT_ID {
+                if xlogrec.xl_rmid == pg_constants::RM_XACT_ID {
                     // Transaction manager stuff
                     let info = xlogrec.xl_info & pg_constants::XLOG_XACT_OPMASK;
                     let tag_blknum = match tag {
@@ -376,14 +370,9 @@ impl PostgresRedoManagerInternal {
                         }
                     }
                 } else if xlogrec.xl_rmid == pg_constants::RM_MULTIXACT_ID {
-                    // Multiexact operations
+                    // Multixact operations
                     let info = xlogrec.xl_info & pg_constants::XLR_RMGR_INFO_MASK;
-                    if info == pg_constants::XLOG_MULTIXACT_ZERO_OFF_PAGE
-                        || info == pg_constants::XLOG_MULTIXACT_ZERO_MEM_PAGE
-                    {
-                        // Just need to zero page
-                        page.copy_from_slice(&ZERO_PAGE);
-                    } else if info == pg_constants::XLOG_MULTIXACT_CREATE_ID {
+                    if info == pg_constants::XLOG_MULTIXACT_CREATE_ID {
                         let xlrec = XlMultiXactCreate::decode(&mut buf);
                         if let ObjectTag::MultiXactMembers(slru) = tag {
                             for i in 0..xlrec.nmembers {