The following makes sense, but looking for suggestions for a workaround that won't affect performance: I have a Map/Reduce script, it is creating invoices from sales orders. We use auto generated numbers but allow override of invoice number. Map/Reduce is creating invoices with duplicate transaction numbers. Currently running in 1 queue which defeats the purpose of a Map/Reduce script but does solve the duplicates for the time being.

If you can place a check before creation, that the invoice has not already been created and only then create. You might wanna use 'Applying Transaction' for this in your search. (I hope you are using a saved search in your getInputData())

Thank you