If you look at the music at Levy, you'll see this is not the Jolson song.

You can look at the Al Jolson Society web site and do a search for Mammy, you will find: "The song popularly known as "My Mammy," which to many people defines Al Jolson, was written in 1921 by Sam Lewis & Joe Young, with music by Walter Donaldson, and entitled "The Sun Shines East - The Sun Shines West." It was introduced by William Frawley, known to later generations as Fred Mertz on "I Love Lucy." Legend has it that it was spotted as a potential hit for Jolson, who introduced it in the show Sinbad that year."

I've seen the quote above (repeated elsewhere too) but I don't think it's true.

Mick