To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a method, apparatus, article of manufacture, and data structure related to the maintenance of {HEAD ~ a plurality} of {TAIL ~ join indexes} 
To overcome the limitations in the prior art described above , and to overcome other limitations that will become apparent upon reading and understanding the present specification , the present invention discloses a method , apparatus , article of manufacture , and data structure related to the maintenance of { HEAD ~ a plurality } of { TAIL ~ join indexes }
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