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Task/Hash-join/Ruby/hash-join.rb

@@ -0,0 +1,22 @@
+def hashJoin(table1, index1, table2, index2)
+  # hash phase
+  h = table1.group_by {|s| s[index1]}
+  h.default = []
+  # join phase
+  table2.collect {|r|
+    h[r[index2]].collect {|s| [s, r]}
+  }.flatten(1)
+end
+
+table1 = [[27, "Jonah"],
+          [18, "Alan"],
+          [28, "Glory"],
+          [18, "Popeye"],
+          [28, "Alan"]]
+table2 = [["Jonah", "Whales"],
+          ["Jonah", "Spiders"],
+          ["Alan", "Ghosts"],
+          ["Alan", "Zombies"],
+          ["Glory", "Buffy"]]
+
+hashJoin(table1, 1, table2, 0).each { |row| p row }