util.dbuffer: Add efficient shortcuts for discard() in certain cases
If the buffer is already empty, nothing to do. If we're throwing away the
whole buffer, we can just empty it and avoid read_chunk() (which in turn
may collapse()). These shortcuts are much more efficient.
-- 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