While others saying 50T DB is relatively normal, personally I can't imagine myself dealing with that sort of data which is always online. If I were them, I'd ask myself, could we archive this data into split chunks? Is this archive even required to be online? What is the size of a subset that has actuality? And so on. Of course they have answers to that and they are generally "no", but my imagination just stops here.
Some time ago when I studied bitcoin ledger structure, I was confused about how it does sum up all transactions to get the balance so quickly, like we in accounting usually do, with the help of some period caching, which is another point of failure and maintenance. Bitcoin is a large enough database to not do that easily. Few docs later I realized that it doesn't do this:
mining -> A 1
A -> B 0.2
(sum(A) == 0.8)
And instead it does this:
mining -> A 1
A -> (B 0.2; A 0.8)
(last(A) == 0.8)
No sums required, all balances are checked by essentially "lookup the latest appearance in a db", where lookup also involves some merkle trees optimization, which I didn't understand enough to remember.
I was confused about how it does sum up all transactions to get the balance so quickly, like we in accounting usually do
For what it's worth, in a system design context, this is called event sourcing (in more general terms it's just a fold, though the idea of event sourcing doesn't preclude caching). I worked at a bank for a few years and this was how we calculated balances too.
And instead it does this:
I don't quite follow you here. It does something distinct from either a fold or caching the current total? (Do you mean that each transaction encodes the resultant balance?)
If the input is worth 50 BTC but you only want to send 25 BTC, Bitcoin will create two outputs worth 25 BTC: one to the destination, and one back to you (known as "change", though you send it to yourself). Any input bitcoins not redeemed in an output is considered a transaction fee; whoever generates the block can claim it by inserting it into the coinbase transaction of that block.
I.e. any "input" is spent completely by a transaction and this makes it irrelevant to future calculations.
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While others saying 50T DB is relatively normal, personally I can't imagine myself dealing with that sort of data which is always online. If I were them, I'd ask myself, could we archive this data into split chunks? Is this archive even required to be online? What is the size of a subset that has actuality? And so on. Of course they have answers to that and they are generally "no", but my imagination just stops here.
Some time ago when I studied bitcoin ledger structure, I was confused about how it does sum up all transactions to get the balance so quickly, like we in accounting usually do, with the help of some period caching, which is another point of failure and maintenance. Bitcoin is a large enough database to not do that easily. Few docs later I realized that it doesn't do this:
And instead it does this: No sums required, all balances are checked by essentially "lookup the latest appearance in a db", where lookup also involves some merkle trees optimization, which I didn't understand enough to remember.For what it's worth, in a system design context, this is called event sourcing (in more general terms it's just a fold, though the idea of event sourcing doesn't preclude caching). I worked at a bank for a few years and this was how we calculated balances too.
I don't quite follow you here. It does something distinct from either a fold or caching the current total? (Do you mean that each transaction encodes the resultant balance?)
Not the entire balance, because a single wallet may have many "inputs", but that's just an implementation detail, as far as I understand it.
https://en.bitcoin.it/wiki/Transaction
If the input is worth 50 BTC but you only want to send 25 BTC, Bitcoin will create two outputs worth 25 BTC: one to the destination, and one back to you (known as "change", though you send it to yourself). Any input bitcoins not redeemed in an output is considered a transaction fee; whoever generates the block can claim it by inserting it into the coinbase transaction of that block.
I.e. any "input" is spent completely by a transaction and this makes it irrelevant to future calculations.
See also: https://bitcoin.stackexchange.com/questions/13069/how-does-t...