Add support for asynchronous notifications

If a notification handler is set using

  db:set_notifier(cb)

then the event loop will be kept alive until
db:close() is called or the event loop.

Prior to this a database connection would
never keep the event loop running.

https://www.postgresql.org/docs/current/libpq-notify.html

Signed-off-by: Asbjørn Sloth Tønnesen <ast@2e8.dk>

1 files changed, 20 insertions, 6 deletions

diff --git a/lem/postgres/queued.lua b/lem/postgres/queued.lua
index 2f597f4..f405dc0 100644
--- a/lem/postgres/queued.lua
+++ b/lem/postgres/queued.lua
@@ -1,6 +1,7 @@
 --
 -- This file is part of lem-postgres.
 -- Copyright 2011 Emil Renner Berthing
+-- Copyright 2020 Asbjørn Sloth Tønnesen
 --
 -- lem-postgres is free software: you can redistribute it and/or
 -- modify it under the terms of the GNU General Public License as
@@ -22,18 +23,32 @@ local postgres = require 'lem.postgres'
 local remove = table.remove
 local thisthread, suspend, resume = utils.thisthread, utils.suspend, utils.resume
 
+local Connection = postgres.Connection
+
 local QConnection = {}
 QConnection.__index = QConnection
 
+function QConnection:set_notifier(cb)
+	Connection.set_notifier(self.conn, cb)
+end
+
+local function cancel_all(t)
+	for i = 1, t.n - 1 do
+		resume(t[i])
+		t[i] = nil
+	end
+end
+
 function QConnection:close()
 	local ok, err = self.conn:close()
-	for i = 1, self.n - 1 do
-		resume(self[i])
-		self[i] = nil
-	end
+	cancel_all(self)
 	return ok, err
 end
-QConnection.__gc = QConnection.close
+
+function QConnection:__gc()
+	cancel_all(self)
+	self.conn = nil
+end
 
 local function lock(self)
 	local n = self.n
@@ -64,7 +79,6 @@ local function wrap(method)
 	end
 end
 
-local Connection = postgres.Connection
 QConnection.exec    = wrap(Connection.exec)
 QConnection.prepare = wrap(Connection.prepare)
 QConnection.run     = wrap(Connection.run)