App engine bulk loader download warning “No descending index on __key__, performing serial download”

Question

I\'m using the following to download all instances of one of my kinds:

appcfg.py download_data --config_file=bulkloader.yaml --kind=ModelName --filename=Mode         


        

Answer 1

As the error describes, without a descending index on __key__ for the model you're downloading, the bulkloader has to download serially. If you add the index as described, it will be able to download in parallel. If you don't, it will work fine, but will be slower to download, as it operates serially.

Note that an additional index has only a small impact on latency, as index rows are written in parallel to the entity write, meaning the write only takes as long as the slowest update.