From 9eea3da810fcda5f614344d310adede5977a4ee6 Mon Sep 17 00:00:00 2001
From: Bojan Serafimov <bojan@pop-os.localdomain>
Date: Mon, 2 May 2022 15:36:03 -0400
Subject: [PATCH] WIP

---
 Cargo.lock                        |  1 +
 pageserver/Cargo.toml             |  1 +
 pageserver/src/bin/linked_redo.rs |  4 ++++
 pageserver/src/walredo.rs         | 19 +++++++++++++++++++
 4 files changed, 25 insertions(+)
 create mode 100644 pageserver/src/bin/linked_redo.rs

diff --git a/Cargo.lock b/Cargo.lock
index 58125ca41c..3dfde91463 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1640,6 +1640,7 @@ dependencies = [
  "hyper",
  "itertools",
  "lazy_static",
+ "libloading",
  "metrics",
  "nix",
  "once_cell",
diff --git a/pageserver/Cargo.toml b/pageserver/Cargo.toml
index 23c16dd5be..114110e273 100644
--- a/pageserver/Cargo.toml
+++ b/pageserver/Cargo.toml
@@ -62,6 +62,7 @@ postgres_ffi = { path = "../libs/postgres_ffi" }
 metrics = { path = "../libs/metrics" }
 utils = { path = "../libs/utils" }
 workspace_hack = { version = "0.1", path = "../workspace_hack" }
+libloading = "0.7.0"
 
 [dev-dependencies]
 hex-literal = "0.3"
diff --git a/pageserver/src/bin/linked_redo.rs b/pageserver/src/bin/linked_redo.rs
new file mode 100644
index 0000000000..ecd1952e2f
--- /dev/null
+++ b/pageserver/src/bin/linked_redo.rs
@@ -0,0 +1,4 @@
+
+fn main() {
+    pageserver::walredo::linked_redo().unwrap();
+}
diff --git a/pageserver/src/walredo.rs b/pageserver/src/walredo.rs
index 6338b839ae..3805373400 100644
--- a/pageserver/src/walredo.rs
+++ b/pageserver/src/walredo.rs
@@ -163,6 +163,23 @@ pub enum WalRedoError {
     InvalidRecord,
 }
 
+pub fn linked_redo(
+    // key: Key,
+    // lsn: Lsn,
+    // base_img: Option<Bytes>,
+    // records: Vec<(Lsn, ZenithWalRecord)>,
+) -> Result<Bytes, WalRedoError> {
+    unsafe {
+        let pg_path = "/home/bojan/src/neondatabase/neon/tmp_install/bin/postgres";
+        let pg_lib = libloading::Library::new(pg_path).expect("failed loading pg");
+        // TODO add stringinfo arg
+        let apply_record_fn: libloading::Symbol<unsafe extern fn()> =
+            pg_lib.get(b"ApplyRecord").expect("failed loading ApplyRecord fn");
+    }
+    // TODO actually return something
+    Ok(Bytes::new())
+}
+
 ///
 /// Public interface of WAL redo manager
 ///
@@ -185,6 +202,8 @@ impl WalRedoManager for PostgresRedoManager {
             return Err(WalRedoError::InvalidRequest);
         }
 
+        // return linked_redo(key, lsn, base_img, records);
+
         let mut img: Option<Bytes> = base_img;
         let mut batch_zenith = can_apply_in_zenith(&records[0].1);
         let mut batch_start = 0;