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From: Peter R <peter_r@gmx.com>
In-Reply-To: <CAAS2fgTga_vTfOKrFu_hEzXSfTfg9FRfJ6aL6ginuGFqnbm7=w@mail.gmail.com>
Date: Thu, 29 Oct 2015 21:04:22 -0700
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References: <5631C363.5060705@neomailbox.net>
	<201510290803.52734.luke@dashjr.org>
	<5632DE33.7030600@bitcartel.com>
	<CAAS2fgTga_vTfOKrFu_hEzXSfTfg9FRfJ6aL6ginuGFqnbm7=w@mail.gmail.com>
To: Gregory Maxwell <gmaxwell@gmail.com>
Cc: Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>,
	telemaco <telemaco@neomailbox.net>
Subject: Re: [bitcoin-dev] [patch] Switching Bitcoin Core to sqlite db
Precedence: list


> On Oct 29, 2015, at 8:35 PM, Gregory Maxwell via bitcoin-dev =
<bitcoin-dev@lists.linuxfoundation.org> wrote:
>=20
> On Fri, Oct 30, 2015 at 3:04 AM, Simon Liu via bitcoin-dev
> <bitcoin-dev@lists.linuxfoundation.org> wrote:
>> Given that UTXO storage is considered critical, it seems reasonable =
to
>=20
> This sounds like a misunderstanding of what consensus criticial means.
> It does not mean that it must be right (though obviously that is
> preferable) but that it must be _consistent_, between all nodes.

Can you give a specific example of how nodes that used different =
database technologies might determine different answers to whether a =
given transaction is valid or invalid?  I=E2=80=99m not a database =
expert, but to me it would seem that if all the unspent outputs can be =
found in the database, and if the relevant information about each output =
can be retrieved without corruption, then that=E2=80=99s all that really =
matters as far as the database is concerned.

Let=E2=80=99s use an unspent pay-to-pubkey-hash output as an example: =
Alice spends this to Bob (she signs it properly), the TX propagates =
across the network and=E2=80=A6then what?  Do some nodes disagree on =
whether or not the TX is valid?  What exactly would they disagree on?  =
Are you suggesting that a database bug would cause some nodes to think =
the output was actually already spent, while others can correctly see =
that it=E2=80=99s unspent?  Or maybe some nodes think the output =
doesn=E2=80=99t exist while others do?  Or are you suggesting that the =
details about this output might be retrieved with errors from certain =
databases but correctly from others? =20

I=E2=80=99d like a concrete example to help me understand why more than =
one implementation of something like the UTXO database would be =
unreasonable.   =20

Peter