From 83cce03f6f5b016535ff8973c82dab8d225c35c3 Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Wed, 18 Sep 2019 13:30:15 -0700
Subject: [PATCH] ircd::m::room::state: Add prefetch() support to
 state::history/state::space.

---
 include/ircd/m/room/state_history.h |  3 ++
 include/ircd/m/room/state_space.h   |  4 +++
 ircd/m_room.cc                      | 50 +++++++++++++++++++++++++++++
 3 files changed, 57 insertions(+)

diff --git a/include/ircd/m/room/state_history.h b/include/ircd/m/room/state_history.h
index 40b0cae7a..c054992e7 100644
--- a/include/ircd/m/room/state_history.h
+++ b/include/ircd/m/room/state_history.h
@@ -36,6 +36,9 @@ struct ircd::m::room::state::history
 	event::idx get(std::nothrow_t, const string_view &type, const string_view &state_key) const;
 	event::idx get(const string_view &type, const string_view &state_key) const;
 
+	bool prefetch(const string_view &type, const string_view &state_key) const;
+	bool prefetch(const string_view &type) const;
+
 	history(const m::room &, const int64_t &bound);
 	history(const m::room::id &, const m::event::id &);
 	history(const m::room &);
diff --git a/include/ircd/m/room/state_space.h b/include/ircd/m/room/state_space.h
index 3810d13df..21fdf6f7e 100644
--- a/include/ircd/m/room/state_space.h
+++ b/include/ircd/m/room/state_space.h
@@ -39,6 +39,10 @@ struct ircd::m::room::state::space
 	bool has(const string_view &type, const string_view &state_key) const;
 	bool has(const string_view &type) const;
 
+	bool prefetch(const string_view &type, const string_view &state_key, const int64_t &depth) const;
+	bool prefetch(const string_view &type, const string_view &state_key) const;
+	bool prefetch(const string_view &type) const;
+
 	space(const m::room &);
 };
 
diff --git a/ircd/m_room.cc b/ircd/m_room.cc
index 619dc9a76..55887cad4 100644
--- a/ircd/m_room.cc
+++ b/ircd/m_room.cc
@@ -2580,6 +2580,21 @@ ircd::m::room::state::history::history(const m::room &room,
 {
 }
 
+bool
+ircd::m::room::state::history::prefetch(const string_view &type)
+const
+{
+	return prefetch(type, string_view{});
+}
+
+bool
+ircd::m::room::state::history::prefetch(const string_view &type,
+                                        const string_view &state_key)
+const
+{
+	return space.prefetch(type, state_key, bound);
+}
+
 ircd::m::event::idx
 ircd::m::room::state::history::get(const string_view &type,
                                    const string_view &state_key)
@@ -2725,6 +2740,41 @@ ircd::m::room::state::space::space(const m::room &room)
 {
 }
 
+bool
+ircd::m::room::state::space::prefetch(const string_view &type)
+const
+{
+	return prefetch(type, string_view{});
+}
+
+bool
+ircd::m::room::state::space::prefetch(const string_view &type,
+                                      const string_view &state_key)
+const
+{
+	return prefetch(type, state_key, -1);
+}
+
+bool
+ircd::m::room::state::space::prefetch(const string_view &type,
+                                      const string_view &state_key,
+                                      const int64_t &depth)
+const
+{
+	const int64_t &_depth
+	{
+		type? depth : 0L
+	};
+
+	char buf[dbs::ROOM_STATE_SPACE_KEY_MAX_SIZE];
+	const string_view &key
+	{
+		dbs::room_state_space_key(buf, room.room_id, type, state_key, _depth, 0UL)
+	};
+
+	return db::prefetch(dbs::room_state_space, key);
+}
+
 bool
 ircd::m::room::state::space::has(const string_view &type)
 const