How to get unique values from loop function for watcher subject

Elastic Stack Elasticsearch
1 

I have used {{#ctx.payload.hits.hits}} {{_source.name}} {{/ctx.payload.hits.hits}} function in the subject of the watcher. Its printing all values with duplicates, can someone please help me how to get Unique values from result set of above.

e.g: 
{{#ctx.payload.hits.hits}} {{_source.name}} {{/ctx.payload.hits.hits}} returning like below
{0:alpha} {0:alpha} {0:beta} {0:alpha}

I need only {0:alpha} {0:beta} vlaues

Thank you in advance
2

Please can someone give me some idea, how to proceed further.

Thank you!