A few corrections:
1. Not swords, but sabres. Polish Army hasn't used swords since XVI or even XV century and as the first army in Europe adopted sabers.
2. Not spears, but lances. Why did Polish cavalry use lances? What do you think? Its not so difficult

If somebody lies on the ground how would be easier to kill him? Using sabre or lance? Good answer - a lance. The same if you meet enemy cavalry group, which is armed with sabres only.
There should be not surprise for you. Polish cavalry was always a swift model for Poland's opponents. They learnt from Poles and tried to imitate Polish cavalry. The same Poland tried to imitate her opponent's infantry. However to be honest our opponents learnt faster, than we. There were many fundametalists in Poland, who didn't want to introduce military reforms and didn't obey a king...
The first major battle with Polish cavalry using lances took place in Albuhera in Spain, on May 16th 1811. In that day a small group of Polish cavalry defeated far advantegous British forces, breaking British infantry squares, killing a few thousand soldiers and capturing a few British banners. Nobody other achieved it again during the Napoleonic Wars...
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There were a few cavalry-cavalry engagements during Polish campaign in 1939. They ended (talking mildly) really not good for the Germans... Besides the lances were very useful to attack German infantry, that hid in swamp area.