combine multi value field with single value field in json

[Cbr1sg]

Hi all,

I have this json file like below:

rootfield: [[-]	
     {[-]	       
       field 1: A       
       field 2: [[-]	
         value1
         value2	
       ]
     }
     {[-]	       
       field 1: B       
       field 2: [[-]	
         value1
         value2
         value3
         value4
       ]
     }
     {[-]	       
       field 1: C       
       field 2: [[-]	
         value1
         value3
         value4
       ]
     }

I want to extract the result to look like this

A_value1,value2
B_value1,value2,value3,value4
C_value1,value3,value4

i know combination of spath and mvexpand will work but I want to avoid mvexpand because it's eating memory and our json file is huge. Would be nice to be able to get the data without mvexpand.

Thanks