Hash join: Difference between revisions

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=={{header|Ruby}}==

<lang ruby>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 }</lang>

{{out}}

<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"]]