How do I iterate through array in Kusto?

Question

I need to iterate through managed data disks in Azure Resource Graph Explorer (https://preview.portal.azure.com/). My query is below but it returns JSON array, I need to extract name of disk and type of storage account which is being used (sample JSON return is below). So I'd like to see on screen grouping by machine name, disk name and then storage account type. My current query is below but obviously it does not work due to return of JSON

where type =~ 'Microsoft.Compute/virtualmachines' |
extend disks = properties.storageProfile.dataDisks |
project name, disks

Same JSON output

[
    {
        "name": "COMP02_DDisk1",
        "createOption": "Attach",
        "diskSizeGB": 400,
        "managedDisk": {
            "id": "/subscriptions/5f5c5be9-77d4db790171/resourceGroups/BRAZILSOUTHDB/providers/Microsoft.Compute/disks/COMP02_DDisk1",
            "storageAccountType": "Premium_LRS"
        },
        "caching": "None",
        "toBeDetached": false,
        "lun": 0,
        "writeAcceleratorEnabled": false
    },
    {
        "name": "COMP02_DDisk2",
        "createOption": "Attach",
        "diskSizeGB": 400,
        "managedDisk": {
            "id": "/subscriptions/5f5c5be9-77d4db790171/resourceGroups/BRAZILSOUTHDB/providers/Microsoft.Compute/disks/COMP02_DDisk2",
            "storageAccountType": "Premium_LRS"
        },
        "caching": "None",
        "toBeDetached": false,
        "lun": 1,
        "writeAcceleratorEnabled": false
    }
]

Answer 1

in such cases, it's usually helpful to use mv-expand to expand the array and then apply the dynamic-property accessors foreach record.

https://docs.microsoft.com/en-us/azure/kusto/query/mvexpandoperator

example:

print d = dynamic([
    {
        "name": "COMP02_DDisk1",
        "createOption": "Attach",
        "diskSizeGB": 400,
        "managedDisk": {
            "id": "/subscriptions/5f5c5be9-77d4db790171/resourceGroups/BRAZILSOUTHDB/providers/Microsoft.Compute/disks/COMP02_DDisk1",
            "storageAccountType": "Premium_LRS"
        },
        "caching": "None",
        "toBeDetached": false,
        "lun": 0,
        "writeAcceleratorEnabled": false
    },
    {
        "name": "COMP02_DDisk2",
        "createOption": "Attach",
        "diskSizeGB": 400,
        "managedDisk": {
            "id": "/subscriptions/5f5c5be9-77d4db790171/resourceGroups/BRAZILSOUTHDB/providers/Microsoft.Compute/disks/COMP02_DDisk2",
            "storageAccountType": "Premium_LRS"
        },
        "caching": "None",
        "toBeDetached": false,
        "lun": 1,
        "writeAcceleratorEnabled": false
    }
])
| mv-expand d
| project d.name, d.managedDisk.storageAccountType

which will output:

| d_name        | d_managedDisk_storageAccountType |
|---------------|----------------------------------|
| COMP02_DDisk1 | Premium_LRS                      |
| COMP02_DDisk2 | Premium_LRS                      |