Hash join: Difference between revisions

=={{header|Nim}}==

<lang Nim>import strformat, tables

type

Data1 = tuple[value: int; key: string]

Data2 = tuple[key: string; value: string]

proc `$`(d: Data1 | Data2): string = &"({d[0]}, {d[1]})"

iterator hashJoin(table1: openArray[Data1]; table2: openArray[Data2]): tuple[a: Data1; b: Data2] =

# Hash phase.

var h: Table[string, seq[Data1]]

for s in table1:

h.mgetOrPut(s.key, @[]).add(s)

# Join phase.

for r in table2:

for s in h[r.key]:

yield (s, r)

let table1 = [(27, "Jonah"),

(18, "Alan"),

(28, "Glory"),

(18, "Popeye"),

(28, "Alan")]

let table2 = [("Jonah", "Whales"),

("Jonah", "Spiders"),

("Alan", "Ghosts"),

("Alan", "Zombies"),

("Glory", "Buffy")]

for row in hashJoin(table1, table2):

echo row.a, " ", row.b</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)</pre>