Shell Programming and Scripting

I have a file arg_file
a1, b1, c1...
a2, b2, c2...
a3, b3, c3...
a4, b4, c4...
a5, b5, c5...
a6, b6, c6...
a7, b7, c7...
a8, b8, c8...
a9, b9, c9...

I have another file pat_file
a2
a5
a9

I want to create an output file which does not contains the values found pat_file :
a1, b1, c1...
a3, b3, c3...
a4, b4, c4...
a6, b6, c6...
a7, b7, c7...
a8, b8, c8...

Currently I am using `grep -v -f pat_file arg_file > outputfile`. But this is taking very long to process ..is there an efficient soultion to this.
My files may contain peak time approx. 90K records too.

Thanks
Amruta

Code:

awk -F, 'NR==FNR{arr[$1]=$0} NR!=FNR{arr[$1]=""} END{for(i in arr) if(arr[i]!="") print arr[i]} filename1 filename2
filename1 --> file with all the data (arg_file)
filename2 --> file with columns that needs to be removed (pat_file)

Code:

awk -F"," ' FNR == NR { arr[$0]=1; next } !arr[$1] ' pat_file arg_file

Code:

join -t, -1 1 -v 1 arg_file pat_file