You are correct in thinking that the solubility of a gas will decrease when a solution of the gas is heated but the solubility of a gas in a solution will decrease when the pressure over the solution is decreased.

This is Henry's law and it is easy to remember if you think about what happens when you open a container of pop. The carbon dioxide bubbles out of the solution...at times, faster than we want it to...because the pressure within the bottle or can is higher than atmospheric pressure. You have decreased the pressure over the solution.