How to reference to doc ids in reduce() function in view

I have a map function like this
map(doc, meta){
emit(doc.txId, null);

I want to get a list of doc ids by grouping on txId. How does my reduce function look like? Is emitting the doc id as value the only way to do that?



So yes if you need it, the only way that I know is to emit it as a value.

But why not query your index on the txId directly and get the list of id from the query instead of a reduce function?

If you do a query, on your index with a specific doc.txId it will return all doc ID for this tx no?