Cucumbers are High in Potassium which is Alkalizing, but "IF" the cucumbers are raised with potassium nitrate, like is done commercially in most cases, then the cucumbers could also be high in Funny Protein, so "IF" you start having problems of becomming too Acidic from eating cucumbers, then they may be of poor quality!
But, "IF" the cucumbers taste sweet, then they are probably of Good Quality!