JJoin performs relational joins on streams of JSON objects. This allows you to treat streams of JSON obects similarly to relational tables.
Join performs inner, outer, left-outer and right-outer along with symmetric difference and difference.
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Let's assume you have to files containing the following JSON:
file1:
{ "id": "L1", f1": "v1" }
{ "id": "L2", f1": "v2" }
file2:
{ "id": "R1", f1": "v1" }
{ "id": "R2", f1": "v3" }
The inner join returns:
> jjoin inner --left file1 --right file2 --using {{f1}}
{
"left": {
"f1": "v1",
"id": "L1"
},
"right": {
"f1": "v1",
"id": "R1"
}
}
The joins use two files containing JSON streams: --left and --right. These streams are
either dictionaries or simple strings. These can be shorted to -l and -r.
You can choose separate keys for the left and the right.
file1:
{ "hostname": "foo.example.com", "ip": "172.17.31.20" }
file2:
{ "instance": "i78648798734", "private-ip": "172.17.31.20" }
> jjoin inner --left file1 --right file2 --left-key {{ip}} --right-key {{private-ip}}
{
"left": {
"hostname": "foo.example.com",
"ip": "172.17.31.20"
},
"right": {
"instance": "i78648798734",
"private-ip": "172.17.31.20"
}
}
Keys are a dot separated path of components from outer to inner. The key
a.b.c would select v1 from the dictionary:
{
"a": {
"b": {
"c": {
"v1"
}
}
}
}
The key . allows you to join with a string stream:
file1:
{ "hostname": "bar.example.com"}
{ "hostname": "baz.example.com"}
file2:
"foo.example.com"
"bar.example.com"
"baz.example.com"
> jjoin inner --left file1 --right file2 --left-key {{hostname}} --right-key {{.}}
{
"left": {
"hostname": "baz.example.com"
}
"right": "baz.examle.com"
}
{
"left": {
"hostname": "bar.example.com"
}
"right": "bar.examle.com"
}
If the key does not exist within an object in the stream, then the object is excluded from the join.
All of these examples use the original files:
file1:
{ "id": "L1", f1": "v1" }
{ "id": "L2", f1": "v2" }
file2:
{ "id": "R1", f1": "v1" }
{ "id": "R2", f1": "v3" }
The outer join returns:
> jjoin outer --left file1 --right file2 --using f1
{
"left": {
"f1": "v1",
"id": "L1"
},
"right": {
"f1": "v1",
"id": "R1"
}
}
{
"left": {
"f1": "v2",
"id": "L2"
},
"right": null
}
{
"left": null,
"right": {
"f1": "v3",
"id": "R2"
}
}
The left-outer join returns:
> jjoin left-outer --left file1 --right file2 --using f1
{
"left": {
"f1": "v1",
"id": "L1"
},
"right": {
"f1": "v1",
"id": "R1"
}
}
{
"left": {
"f1": "v2",
"id": "L2"
},
"right": null
}
The right-outer join returns:
> jjoin right-outer --left file1 --right file2 --using {{f1}}
{
"left": {
"f1": "v1",
"id": "L1"
},
"right": {
"f1": "v1",
"id": "R1"
}
}
{
"left": null,
"right": {
"f1": "v3",
"id": "R2"
}
}
The symm-diff join returns:
> jjoin symm-diff --left file1 --right file2 --using {{f1}}
{
"left": {
"f1": "v2",
"id": "L2"
},
"right": null
}
{
"left": null,
"right": {
"f1": "v3",
"id": "R2"
}
}
The subtract join returns:
> jjoin subtract --left file1 --right file2 --using {{f1}}
{
"f1": "v2",
"id": "L2"
}