I think it's either Plas Johnson, Cornell Dupree or Bernard Purdie. Probably Plas. I think Purdie's 7,000 recording sessions may be an exaggeration. Plas claims over 5,000. Idris Muhammad must be up there somewhere, too.
Then there are all those guys like Bernie Glow, Al Klink and Romeo Penque, who seemed to work on every record ever made in Hollywood. 'Course, they may not count as jazz musicians
MG