take a long runtime for vLookup from another table

Dear Community,

I have 2 table. Table A have 2 column (ID and jobnumber)

Table B is the details of ID. I created a new column (Count Job) in table B  to count how many jobnumber inside the ID. 

DAX I used, 
Count Job = CALCULATE(DISTINCTCOUNT(TableA[JobNumber]),FILTER(TableA,TableA[ID]=Table[ID]))

Example (Table A)

Table B 

Since I have huge data, the runtime for this DAX is more than 3 hours. 
So would like to ask is any other way to get the same solution.

Thanks for your attention. Any help provided will be greatly appreciated.