Implement fastresume for postgres

Makefile

@@ -27,7 +27,7 @@ devserver-postgres:
 	echo -n '' > /tmp/rqbit-log && cargo run -- \
 		--log-file /tmp/rqbit-log \
 		--log-file-rust-log=debug,librqbit=trace \
-		server start --persistence-config postgres:///rqbit /tmp/scratch/
+		server start --fastresume --persistence-config postgres:///rqbit /tmp/scratch/
 
 @PHONY: clean
 clean:

crates/librqbit/src/session_persistence/postgres.rs

@@ -8,7 +8,7 @@ use anyhow::Context;
 use futures::{stream::BoxStream, StreamExt};
 use librqbit_core::Id20;
 use sqlx::{Pool, Postgres};
-use tracing::debug;
+use tracing::error_span;
 
 use super::{SerializedTorrent, SessionPersistenceStore};
 
@@ -55,12 +55,20 @@ impl PostgresSessionStorage {
             .connect(connection_string)
             .await?;
 
-        sqlx::query("CREATE SEQUENCE IF NOT EXISTS torrents_id AS integer;")
-            .execute(&pool)
-            .await
-            .context("error executing CREATE SEQUENCE")?;
+        macro_rules! exec {
+            ($q:expr) => {
+                sqlx::query($q)
+                    .execute(&pool)
+                    .await
+                    .context($q)
+                    .context("error running query")?;
+            };
+        }
 
-        let create_q = "CREATE TABLE IF NOT EXISTS torrents (
+        exec!("CREATE SEQUENCE IF NOT EXISTS torrents_id AS integer;");
+
+        exec!(
+            "CREATE TABLE IF NOT EXISTS torrents (
           id INTEGER PRIMARY KEY DEFAULT nextval('torrents_id'),
           info_hash BYTEA NOT NULL,
           torrent_bytes BYTEA NOT NULL,
@@ -68,11 +76,10 @@ impl PostgresSessionStorage {
           output_folder TEXT NOT NULL,
           only_files INTEGER[],
           is_paused BOOLEAN NOT NULL
-        )";
-        sqlx::query(create_q)
-            .execute(&pool)
-            .await
-            .context("error executing CREATE TABLE")?;
+        )"
+        );
+
+        exec!("ALTER TABLE torrents ADD COLUMN IF NOT EXISTS have_bitfield BYTEA");
 
         Ok(Self { pool })
     }
@@ -172,18 +179,131 @@ impl SessionPersistenceStore for PostgresSessionStorage {
     }
 }
 
+struct PgBitfield {
+    torrent_id: TorrentIdOrHash,
+    inmem: BF,
+    pool: Pool<Postgres>,
+}
+
+impl BitV for PgBitfield {
+    fn as_slice(&self) -> &bitvec::prelude::BitSlice<u8, bitvec::prelude::Msb0> {
+        self.inmem.as_bitslice()
+    }
+
+    fn as_slice_mut(&mut self) -> &mut bitvec::prelude::BitSlice<u8, bitvec::prelude::Msb0> {
+        self.inmem.as_mut_bitslice()
+    }
+
+    fn into_dyn(self) -> Box<dyn BitV> {
+        Box::new(self)
+    }
+
+    fn as_bytes(&self) -> &[u8] {
+        self.inmem.as_raw_slice()
+    }
+
+    fn flush(&mut self) -> anyhow::Result<()> {
+        // TODO: make flush async, and don't spawn this, to avoid allocations and capture the result.
+        crate::spawn_utils::spawn(
+            "pg",
+            error_span!("pg_update_bitfield", id=?self.torrent_id),
+            {
+                let hb = self.as_bytes().to_owned();
+                let pool = self.pool.clone();
+                let torrent_id = self.torrent_id;
+
+                macro_rules! exec {
+                    ($q:expr, $bf:expr, $id:expr) => {
+                        sqlx::query($q)
+                            .bind($bf)
+                            .bind($id)
+                            .execute(&pool)
+                            .await
+                            .context($q)
+                            .context("error executing query")
+                    };
+                }
+
+                async move {
+                    match torrent_id {
+                        TorrentIdOrHash::Id(id) => {
+                            let id: i32 = id.try_into()?;
+                            exec!(
+                                "UPDATE torrents SET have_bitfield = $1 WHERE id = $2",
+                                &hb,
+                                id
+                            )?;
+                        }
+                        TorrentIdOrHash::Hash(h) => {
+                            exec!(
+                                "UPDATE torrents SET have_bitfield = $1 WHERE info_hash = $2",
+                                &hb,
+                                &h.0[..]
+                            )?;
+                        }
+                    };
+                    Ok(())
+                }
+            },
+        );
+        Ok(())
+    }
+}
+
 #[async_trait::async_trait]
 impl BitVFactory for PostgresSessionStorage {
-    async fn load(&self, _: TorrentIdOrHash) -> anyhow::Result<Option<Box<dyn BitV>>> {
-        debug!("BitVFactory not implemented for PostgresSessionStorage: fastresume not available");
-        Ok(None)
+    async fn load(&self, id: TorrentIdOrHash) -> anyhow::Result<Option<Box<dyn BitV>>> {
+        #[derive(sqlx::FromRow)]
+        struct HaveBitfield {
+            have_bitfield: Option<Vec<u8>>,
+        }
+
+        macro_rules! exec {
+            ($q:expr, $v:expr) => {
+                sqlx::query_as($q)
+                    .bind($v)
+                    .fetch_one(&self.pool)
+                    .await
+                    .context($q)
+                    .context("error executing query")?
+            };
+        }
+
+        let hb: HaveBitfield = match id {
+            TorrentIdOrHash::Id(id) => {
+                let id: i32 = id.try_into()?;
+                exec!("SELECT have_bitfield FROM torrents WHERE id = $1", id)
+            }
+            TorrentIdOrHash::Hash(h) => {
+                exec!(
+                    "SELECT have_bitfield FROM torrents WHERE info_hash = $1",
+                    &h.0[..]
+                )
+            }
+        };
+
+        let hb = hb.have_bitfield;
+        Ok(hb.map(|b| {
+            PgBitfield {
+                torrent_id: id,
+                inmem: BF::from_boxed_slice(b.into_boxed_slice()),
+                pool: self.pool.clone(),
+            }
+            .into_dyn()
+        }))
     }
 
     async fn store_initial_check(
         &self,
-        _: TorrentIdOrHash,
+        id: TorrentIdOrHash,
         b: BF,
     ) -> anyhow::Result<Box<dyn BitV>> {
-        Ok(b.into_dyn())
+        let mut bf = PgBitfield {
+            torrent_id: id,
+            inmem: b,
+            pool: self.pool.clone(),
+        };
+        bf.flush()?;
+        Ok(bf.into_dyn())
     }
 }