util.smqueue: Refactor checkpoint logic and add tests The previous checkpoint logic used recursion, and the code was more complex than needed due to maintenance of the self._next_checkpoint field. This switches to a loop, which should be a bit more efficient, partly because there are fewer calls (although it was a tail call) and because table lookups can now be cached between each execution. _call_checkpoints() is now called unconditionally for every ack, which is simpler though adds a function call, it should be more than balanced out by the other changes.

-- Enables SQL query logging
--
-- luacheck: ignore 213/uri

module:set_global();

local engines = module:shared("/*/sql/connections");

for uri, engine in pairs(engines) do
	engine:debug(true);
end

setmetatable(engines, {
	__newindex = function (t, uri, engine)
		engine:debug(true);
		rawset(t, uri, engine);
	end
});

function module.unload()
	setmetatable(engines, nil);
	for uri, engine in pairs(engines) do
		engine:debug(false);
	end
end