Data commit

Task/Hash-join/Julia/hash-join-1.julia

@@ -0,0 +1,8 @@
+using DataFrames
+
+A = DataFrame(Age = [27, 18, 28, 18, 28], Name = ["Jonah", "Alan", "Glory", "Popeye", "Alan"])
+B = DataFrame(Name = ["Jonah", "Jonah", "Alan", "Alan", "Glory"],
+    Nemesis = ["Whales", "Spiders", "Ghosts", "Zombies", "Buffy"])
+AB = join(A, B, on = :Name)
+
+@show A B AB

Task/Hash-join/Julia/hash-join-2.julia

@@ -0,0 +1,19 @@
+function hashjoin(A::Array, ja::Int, B::Array, jb::Int)
+    M = Dict(t[jb] => filter(l -> l[jb] == t[jb], B) for t in B)
+    return collect([a, b] for a in A for b in get(M, a[ja], ()))
+end
+
+table1 = [(27, "Jonah"),
+          (18, "Alan"),
+          (28, "Glory"),
+          (18, "Popeye"),
+          (28, "Alan")]
+table2 = [("Jonah", "Whales"),
+          ("Jonah", "Spiders"),
+          ("Alan", "Ghosts"),
+          ("Alan", "Zombies"),
+          ("Glory", "Buffy")]
+
+for r in hashjoin(table1, 2, table2, 1)
+    println(r)
+end