Projectig certain sub documents in Kusto - azure-data-explorer

Question

I have a timeseries data which looks like follows
"data": {
"a": {
"T": [
1652167964645,
1652168781684,
1652168781720,
1652169266156,
1652169267146,
1652169272796,
1652169299338
],
"V": [
1,
2,
3,
10,
6,
1252,
1555
]
},
"b": {
"T": [
1652167961657,
1652168781720,
1652168781818,
1652168787377,
1652168835734,
1652169266108,
1652169266125,
1652169272798,
1652169299328
],
"V": [
1,
3,
4,
6,
12,
15,
16,
17,
1
]
},
"c": {
"T": [
1652167960194,
1652168787377,
1652169266108,
1652169272798,
1652169299328
],
"V": [
1,
3,
17,
18,
1
]
}}
inside the sub documents there are time and values
I can process the data in total. but if I want tp process only two sub document how can i do that ?
I can project like following
| project data["a"],data["b"] but then I can not process the time. how can i accomplish it ?
Expected output:
One column with time, and other column ( i.e a, b ) for the values
Time , A , B
0:55, 1,2

Answer 1

let requested_columns = dynamic(["a","b"]);
datatable(data:dynamic)
[
dynamic
(
{
"a": {
"T": [
1652167964645,
1652168781684,
1652168781720,
1652169266156,
1652169267146,
1652169272796,
1652169299338
],
"V": [
1,
2,
3,
10,
6,
1252,
1555
]
},
"b": {
"T": [
1652167961657,
1652168781720,
1652168781818,
1652168787377,
1652168835734,
1652169266108,
1652169266125,
1652169272798,
1652169299328
],
"V": [
1,
3,
4,
6,
12,
15,
16,
17,
1
]
},
"c": {
"T": [
1652167960194,
1652168787377,
1652169266108,
1652169272798,
1652169299328
],
"V": [
1,
3,
17,
18,
1
]
}
}
)
]
| mv-expand data
| extend key = tostring(bag_keys(data)[0])
| where key in (requested_columns)
| mv-expand T = data[key].T to typeof(long), V = data[key].V to typeof(long)
| evaluate pivot(key, take_any(V), T)
| order by T asc
T
a
b
1652167961657
1
1652167964645
1
1652168781684
2
1652168781720
3
3
1652168781818
4
1652168787377
6
1652168835734
12
1652169266108
15
1652169266125
16
1652169266156
10
1652169267146
6
1652169272796
1252
1652169272798
17
1652169299328
1
1652169299338
1555
Fiddle