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NebulousLabs / Sia

Blockchain-based marketplace for file storage. Project has moved to GitLab: https://gitlab.com/NebulousLabs/Sia
https://sia.tech
MIT License
2.71k stars 442 forks source link

Don't aggregate inputs via a parent tx when sending Siacoins #3143

Open huetsch opened 6 years ago

huetsch commented 6 years ago

Currently the wallet module builds 2 transactions each time a user wants to send Siacoins. It does this via the FundSiacoins function. The first transaction aggregates all inputs into an output equalling the desired amount to be sent (and potentially a refund). The second transaction spends the desired amount output from the first transaction and creates an output to the actual desired recipient.

To the best of my knowledge, FundSiacoins is built this way to conveniently support transactions without outputs. In the frequent case where someone just wants to send Siacoins elsewhere, SendSiacoins and SendSiacoinsMulti in their current form seem to create twice as many transactions as necessary. This unnecessarily bloats the blockchain and can slow down the 2nd party's receipt of the Siacoins.

This PR creates a specialized function FundSiacoinsForOutputs to be used in the special case of a transaction that just sends Siacoins to an output or a set of outputs. FundSiacoinsForOutputs eliminates the double transaction issue.

Please let me know if I've missed an intentional design reason for the way the old code worked!

DavidVorick commented 5 years ago

We never built specialized functions for sending siacoins because we were putting our dev hours elsewhere. I haven't looked at this code yet, but there's nothing fundamentally wrong with the idea of using specialized functions to reduce the total overhead of sending money around the Sia platform - it is on our long term todo list.