Add beacon.watch (#3362)

> This is currently a WIP and all features are subject to alteration or removal at any time.

## Overview

The successor to #2873.

Contains the backbone of `beacon.watch` including syncing code, the initial API, and several core database tables.

See `watch/README.md` for more information, requirements and usage.

watch/src/block_packing/database.rs

@@ -0,0 +1,140 @@
+use crate::database::{
+    schema::{beacon_blocks, block_packing},
+    watch_types::{WatchHash, WatchSlot},
+    Error, PgConn, MAX_SIZE_BATCH_INSERT,
+};
+
+use diesel::prelude::*;
+use diesel::{Insertable, Queryable};
+use log::debug;
+use serde::{Deserialize, Serialize};
+use std::time::Instant;
+
+#[derive(Debug, Queryable, Insertable, Serialize, Deserialize)]
+#[diesel(table_name = block_packing)]
+pub struct WatchBlockPacking {
+    pub slot: WatchSlot,
+    pub available: i32,
+    pub included: i32,
+    pub prior_skip_slots: i32,
+}
+
+/// Insert a batch of values into the `block_packing` table.
+///
+/// On a conflict, it will do nothing, leaving the old value.
+pub fn insert_batch_block_packing(
+    conn: &mut PgConn,
+    packing: Vec<WatchBlockPacking>,
+) -> Result<(), Error> {
+    use self::block_packing::dsl::*;
+
+    let mut count = 0;
+    let timer = Instant::now();
+
+    for chunk in packing.chunks(MAX_SIZE_BATCH_INSERT) {
+        count += diesel::insert_into(block_packing)
+            .values(chunk)
+            .on_conflict_do_nothing()
+            .execute(conn)?;
+    }
+
+    let time_taken = timer.elapsed();
+    debug!("Block packing inserted, count: {count}, time taken: {time_taken:?}");
+    Ok(())
+}
+
+/// Selects the row from the `block_packing` table where `slot` is minimum.
+pub fn get_lowest_block_packing(conn: &mut PgConn) -> Result<Option<WatchBlockPacking>, Error> {
+    use self::block_packing::dsl::*;
+    let timer = Instant::now();
+
+    let result = block_packing
+        .order_by(slot.asc())
+        .limit(1)
+        .first::<WatchBlockPacking>(conn)
+        .optional()?;
+
+    let time_taken = timer.elapsed();
+    debug!("Block packing requested: lowest, time_taken: {time_taken:?}");
+    Ok(result)
+}
+
+/// Selects the row from the `block_packing` table where `slot` is maximum.
+pub fn get_highest_block_packing(conn: &mut PgConn) -> Result<Option<WatchBlockPacking>, Error> {
+    use self::block_packing::dsl::*;
+    let timer = Instant::now();
+
+    let result = block_packing
+        .order_by(slot.desc())
+        .limit(1)
+        .first::<WatchBlockPacking>(conn)
+        .optional()?;
+
+    let time_taken = timer.elapsed();
+    debug!("Block packing requested: highest, time_taken: {time_taken:?}");
+    Ok(result)
+}
+
+/// Selects a single row of the `block_packing` table corresponding to a given `root_query`.
+pub fn get_block_packing_by_root(
+    conn: &mut PgConn,
+    root_query: WatchHash,
+) -> Result<Option<WatchBlockPacking>, Error> {
+    use self::beacon_blocks::dsl::{beacon_blocks, root};
+    use self::block_packing::dsl::*;
+    let timer = Instant::now();
+
+    let join = beacon_blocks.inner_join(block_packing);
+
+    let result = join
+        .select((slot, available, included, prior_skip_slots))
+        .filter(root.eq(root_query))
+        .first::<WatchBlockPacking>(conn)
+        .optional()?;
+
+    let time_taken = timer.elapsed();
+    debug!("Block packing requested: {root_query}, time_taken: {time_taken:?}");
+    Ok(result)
+}
+
+/// Selects a single row of the `block_packing` table corresponding to a given `slot_query`.
+pub fn get_block_packing_by_slot(
+    conn: &mut PgConn,
+    slot_query: WatchSlot,
+) -> Result<Option<WatchBlockPacking>, Error> {
+    use self::block_packing::dsl::*;
+    let timer = Instant::now();
+
+    let result = block_packing
+        .filter(slot.eq(slot_query))
+        .first::<WatchBlockPacking>(conn)
+        .optional()?;
+
+    let time_taken = timer.elapsed();
+    debug!("Block packing requested: {slot_query}, time_taken: {time_taken:?}");
+    Ok(result)
+}
+
+/// Selects `slot` from all rows of the `beacon_blocks` table which do not have a corresponding
+/// row in `block_packing`.
+#[allow(dead_code)]
+pub fn get_unknown_block_packing(
+    conn: &mut PgConn,
+    slots_per_epoch: u64,
+) -> Result<Vec<Option<WatchSlot>>, Error> {
+    use self::beacon_blocks::dsl::{beacon_blocks, root, slot};
+    use self::block_packing::dsl::block_packing;
+
+    let join = beacon_blocks.left_join(block_packing);
+
+    let result = join
+        .select(slot)
+        .filter(root.is_null())
+        // Block packing cannot be retrieved for epoch 0 so we need to exclude them.
+        .filter(slot.ge(slots_per_epoch as i32))
+        .order_by(slot.desc())
+        .nullable()
+        .load::<Option<WatchSlot>>(conn)?;
+
+    Ok(result)
+}