Why are events duplicating when running | collect command using output_format=hec?

[Pavankumar]

HI 

I am facing issue when running collect command event are double in new index

test  | collect index=test_1 output_format=hec

if in test index there are 100 event when running collect command  with output_format=hec then event are 200 in test_1 index.

how can I resolved this event duplication.