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Add support for left and right joins #23

Merged
merged 8 commits into from
Jul 13, 2017
Merged

Add support for left and right joins #23

merged 8 commits into from
Jul 13, 2017

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jstcki
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@jstcki jstcki commented Jul 12, 2017

Fixes #21.

I also added a new test file. The results are the following:

# Left
./ndjson-join 'd.name' <(csv2json -n test/a.csv) <(csv2json -n test/c.csv) --left
[{"name":"Fred","color":"red"},{"name":"Fred","number":"42"}]
[{"name":"Alice","color":"green"},null]
[{"name":"Bob","color":"blue"},null]

# Right
./ndjson-join 'd.name' <(csv2json -n test/c.csv) <(csv2json -n test/a.csv) --right
[{"name":"Fred","number":"42"},{"name":"Fred","color":"red"}]
[null,{"name":"Alice","color":"green"}]
[null,{"name":"Bob","color":"blue"}]

# Inner (default)
./ndjson-join 'd.name' <(csv2json -n test/a.csv) <(csv2json -n test/c.csv)
[{"name":"Fred","color":"red"},{"name":"Fred","number":"42"}]

mbostock
mbostock reviewed Jul 12, 2017
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ndjson-join Outdated
@@ -13,6 +13,8 @@ commander
.usage("[options] [expression₀ [expression₁]] <file₀> <file₁>")
.description("Join two newline-delimited JSON streams into a stream of pairs.")
.option("-r, --require <name=module>", "require a module", requires, {d: undefined, i: -1})
.option("--left", "Perform a left join", false)
.option("--right", "Perform a right join", false)
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Lowercase “perform”.

mbostock
mbostock reviewed Jul 12, 2017
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ndjson-join Outdated
@@ -25,6 +27,8 @@ if (commander.args.length < 4) {
commander.args.splice(1, 0, commander.args[0]);
}

var join = commander.left ? leftJoin : commander.right ? rightJoin : innerJoin;

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So if both --left and --right are set, --left takes priority? Perhaps instead, if both are set we should do an outerJoin?

mbostock
mbostock reviewed Jul 12, 2017
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ndjson-join Outdated
map.forEach(function(value, key) {
value[0].forEach(function(v0) {
if (value[1].length === 0) {
output([v0, null])
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Missing semicolon.

mbostock
mbostock reviewed Jul 12, 2017
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ndjson-join Outdated
function leftJoin() {
map.forEach(function(value, key) {
value[0].forEach(function(v0) {
if (value[1].length === 0) {
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I’d invert the logic like so:

if (value[1].length) {
  …
} else {
  output([v0, null]);
}

mbostock
mbostock reviewed Jul 12, 2017
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ndjson-join Outdated
map.forEach(function(value, key) {
value[1].forEach(function(v1) {
if (value[0].length === 0) {
output([null, v1])
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Semicolon.

mbostock
mbostock reviewed Jul 12, 2017
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ndjson-join Outdated
function rightJoin() {
map.forEach(function(value, key) {
value[1].forEach(function(v1) {
if (value[0].length === 0) {
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Invert logic as above.

@mbostock
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Good stuff! Biggest suggestion would be to support outer join either as --left --right or as --outer. (If the latter, then the arguments should be exclusive and specifying multiple types of join should exit with an error.)

Can you update the README to document the new arguments?

@jstcki
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jstcki commented Jul 13, 2017

Done! Thanks for the feedback.

One thing I wondered: wouldn't it be better to output an empty object instead of null for missing values? That might be easier to handle later in the chain because for example Object.assign(null, {foo: 1}) will fail.

@mbostock mbostock merged commit a0b62dd into mbostock:master Jul 13, 2017
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Released in 0.3.1! Thank you!

@mbostock mbostock mentioned this pull request Jul 13, 2017
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@jstcki jstcki deleted the left-right-join branch July 17, 2017 09:42
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