Hash join: Difference between revisions
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Generic hash join. Arguments <code>left-key</code> and <code>right-key</code> are functions applied to the elements of the <code>left</code> and <code>right</code> sequences to retrieve the join key. |
Generic hash join. Arguments <code>left-key</code> and <code>right-key</code> are functions applied to the elements of the <code>left</code> and <code>right</code> sequences to retrieve the join key. |
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<lang txr>@(do |
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(28 Glory) |
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(18 Popeye) |
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(28 Alan))) |
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(defvar nemesis-name '((Jonah Whales) |
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(Jonah Spiders) |
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(Alan Ghosts) |
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(Alan Zombies) |
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(Glory Buffy))) |
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(defun hash-join (left left-key right right-key) |
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(let ((join-hash [group-by left-key left])) ;; hash phase |
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(append-each ((r-entry right)) ;; join phase |
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(collect-each ((l-entry [join-hash [right-key r-entry]])) |
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^(,l-entry ,r-entry))))) |
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(format t "~s\n" [hash-join age-name second nemesis-name first])</lang> |
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</lang> |
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{{out}} |
{{out}} |
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<pre>$ txr hash-join. |
<pre>$ txr hash-join.tl |
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(((27 Jonah) (Jonah Whales)) ((27 Jonah) (Jonah Spiders)) ((18 Alan) (Alan Ghosts)) ((28 Alan) (Alan Ghosts)) ((18 Alan) (Alan Zombies)) ((28 Alan) (Alan Zombies)) ((28 Glory) (Glory Buffy)))</pre> |
(((27 Jonah) (Jonah Whales)) ((27 Jonah) (Jonah Spiders)) ((18 Alan) (Alan Ghosts)) ((28 Alan) (Alan Ghosts)) ((18 Alan) (Alan Zombies)) ((28 Alan) (Alan Zombies)) ((28 Glory) (Glory Buffy)))</pre> |
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