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Date: Tue, 12 May 2015 12:50:16 -0700
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Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] A suggestion for reducing the size of the
UTXO database
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Having thousands of utxos floating around for a single address is clearly a
bad thing - it creates a lot of memory load on bitcoin nodes.
However, having only one utxo for an address is also a bad thing, for
concurrent operations.
Having "several" utxos available to spend is good for parallelism, so that
2 or more tasks which are spending from the same address don't have to line
up single file waiting for one of the tasks to publish a tx first so that
the next task can spend the (unconfirmed) change output of the first.
Requiring/Forcing/Having a single output carry the entire balance of an
address does not work at scale. (Yes, this presumes that the tasks are
coordinated so that they don't attempt to spend the same outputs. Internal
coordination is solvable.)
In multiple replies, you push for having "all" utxos of an address spent in
one transaction. Why all? If the objective is to reduce the size of the
utxo pool, it would be sufficient simply to recommend that wallets and
other spenders consume more utxos than they create, on average.
I'm ok with "consume more utxos than you generate" as a good citizen / best
practices recommendation, but a requirement that all prior outputs must be
spent in one transaction seems excessive and impractical.
-Danny
On Sat, May 9, 2015 at 10:09 AM, Jim Phillips <jim@ergophobia.org> wrote:
> Forgive me if this idea has been suggested before, but I made this
> suggestion on reddit and I got some feedback recommending I also bring it
> to this list -- so here goes.
>
> I wonder if there isn't perhaps a simpler way of dealing with UTXO growth.
> What if, rather than deal with the issue at the protocol level, we deal
> with it at the source of the problem -- the wallets. Right now, the typical
> wallet selects only the minimum number of unspent outputs when building a
> transaction. The goal is to keep the transaction size to a minimum so that
> the fee stays low. Consequently, lots of unspent outputs just don't get
> used, and are left lying around until some point in the future.
>
> What if we started designing wallets to consolidate unspent outputs? When
> selecting unspent outputs for a transaction, rather than choosing just the
> minimum number from a particular address, why not select them ALL? Take all
> of the UTXOs from a particular address or wallet, send however much needs
> to be spent to the payee, and send the rest back to the same address or a
> change address as a single output? Through this method, we should wind up
> shrinking the UTXO database over time rather than growing it with each
> transaction. Obviously, as Bitcoin gains wider adoption, the UTXO database
> will grow, simply because there are 7 billion people in the world, and
> eventually a good percentage of them will have one or more wallets with
> spendable bitcoin. But this idea could limit the growth at least.
>
> The vast majority of users are running one of a handful of different
> wallet apps: Core, Electrum; Armory; Mycelium; Breadwallet; Coinbase;
> Circle; Blockchain.info; and maybe a few others. The developers of all
> these wallets have a vested interest in the continued usefulness of
> Bitcoin, and so should not be opposed to changing their UTXO selection
> algorithms to one that reduces the UTXO database instead of growing it.
>
> From the miners perspective, even though these types of transactions would
> be larger, the fee could stay low. Miners actually benefit from them in
> that it reduces the amount of storage they need to dedicate to holding the
> UTXO. So miners are incentivized to mine these types of transactions with a
> higher priority despite a low fee.
>
> Relays could also get in on the action and enforce this type of behavior
> by refusing to relay or deprioritizing the relay of transactions that don't
> use all of the available UTXOs from the addresses used as inputs. Relays
> are not only the ones who benefit the most from a reduction of the UTXO
> database, they're also in the best position to promote good behavior.
>
> --
> *James G. Phillips IV*
> <https://plus.google.com/u/0/113107039501292625391/posts>
>
> *"Don't bunt. Aim out of the ball park. Aim for the company of immortals."
> -- David Ogilvy*
>
> *This message was created with 100% recycled electrons. Please think
> twice before printing.*
>
>
> ------------------------------------------------------------------------------
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>
>
--001a1140e85ebaf0f60515e7cd35
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
<div dir=3D"ltr">Having thousands of utxos floating around for a single add=
ress is clearly a bad thing - it creates a lot of memory load on bitcoin no=
des.=C2=A0<div><br></div><div>However, having only one utxo for an address =
is also a bad thing, for concurrent operations.=C2=A0<div><br></div><div>Ha=
ving "several" utxos available to spend is good for parallelism, =
so that 2 or more tasks which are spending from the same address don't =
have to line up single file waiting for one of the tasks to publish a tx fi=
rst so that the next task can spend the (unconfirmed) change output of the =
first. Requiring/Forcing/Having a single output carry the entire balance of=
an address does not work at scale. (Yes, this presumes that the tasks are =
coordinated so that they don't attempt to spend the same outputs. Inter=
nal coordination is solvable.)<br></div><div><br></div><div>In multiple rep=
lies, you push for having "all" utxos of an address spent in one =
transaction.=C2=A0 Why all?=C2=A0 If the objective is to reduce the size of=
the utxo pool, it would be sufficient simply to recommend that wallets and=
other spenders consume more utxos than they create, on average. =C2=A0</di=
v><div><br></div><div>I'm ok with "consume more utxos than you gen=
erate" as a good citizen / best practices recommendation, but a requir=
ement that all prior outputs must be spent in one transaction seems excessi=
ve and impractical.</div><div><br></div><div>-Danny</div></div><div class=
=3D"gmail_extra"><br><div class=3D"gmail_quote">On Sat, May 9, 2015 at 10:0=
9 AM, Jim Phillips <span dir=3D"ltr"><<a href=3D"mailto:jim@ergophobia.o=
rg" target=3D"_blank">jim@ergophobia.org</a>></span> wrote:<br><blockquo=
te class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc so=
lid;padding-left:1ex"><div dir=3D"ltr"><div>Forgive me if this idea has bee=
n suggested before, but I made this suggestion on reddit and I got some fee=
dback recommending I also bring it to this list -- so here goes.</div><div>=
<br></div><div>I wonder if there isn't perhaps a simpler way of dealing=
with UTXO growth. What if, rather than deal with the issue at the protocol=
level, we deal with it at the source of the problem -- the wallets. Right =
now, the typical wallet selects only the minimum number of unspent outputs =
when building a transaction. The goal is to keep the transaction size to a =
minimum so that the fee stays low. Consequently, lots of unspent outputs ju=
st don't get used, and are left lying around until some point in the fu=
ture.</div><div><br></div><div>What if we started designing wallets to cons=
olidate unspent outputs? When selecting unspent outputs for a transaction, =
rather than choosing just the minimum number from a particular address, why=
not select them ALL? Take all of the UTXOs from a particular address or wa=
llet, send however much needs to be spent to the payee, and send the rest b=
ack to the same address or a change address as a single output? Through thi=
s method, we should wind up shrinking the UTXO database over time rather th=
an growing it with each transaction. Obviously, as Bitcoin gains wider adop=
tion, the UTXO database will grow, simply because there are 7 billion peopl=
e in the world, and eventually a good percentage of them will have one or m=
ore wallets with spendable bitcoin. But this idea could limit the growth at=
least.</div><div><br></div><div>The vast majority of users are running one=
of a handful of different wallet apps: Core, Electrum; Armory; Mycelium; B=
readwallet; Coinbase; Circle; Blockchain.info; and maybe a few others. The =
developers of all these wallets have a vested interest in the continued use=
fulness of Bitcoin, and so should not be opposed to changing their UTXO sel=
ection algorithms to one that reduces the UTXO database instead of growing =
it.</div><div><br></div><div>From the miners perspective, even though these=
types of transactions would be larger, the fee could stay low. Miners actu=
ally benefit from them in that it reduces the amount of storage they need t=
o dedicate to holding the UTXO. So miners are incentivized to mine these ty=
pes of transactions with a higher priority despite a low fee.</div><div><br=
></div><div>Relays could also get in on the action and enforce this type of=
behavior by refusing to relay or deprioritizing the relay of transactions =
that don't use all of the available UTXOs from the addresses used as in=
puts. Relays are not only the ones who benefit the most from a reduction of=
the UTXO database, they're also in the best position to promote good b=
ehavior.</div><div><div><div><br></div><div>--<div><b>James G. Phillips IV<=
/b>=C2=A0<a href=3D"https://plus.google.com/u/0/113107039501292625391/posts=
" style=3D"font-size:x-small" target=3D"_blank"><img src=3D"https://ssl.gst=
atic.com/images/icons/gplus-16.png"></a>=C2=A0</div></div><div><font size=
=3D"1"><i>"Don't bunt. Aim out of the ball park. Aim for the compa=
ny of immortals." -- David Ogilvy<br></i></font><div><font size=3D"1">=
<br></font></div></div><div><font size=3D"1"><img src=3D"http://findicons.c=
om/files/icons/1156/fugue/16/leaf.png">=C2=A0<em style=3D"font-family:verda=
na,geneva,sans-serif;line-height:16px;color:green;background-color:rgb(255,=
255,255)">This message was created with 100% recycled electrons. Please thi=
nk twice before printing.</em></font></div></div></div>
</div>
<br>-----------------------------------------------------------------------=
-------<br>
One dashboard for servers and applications across Physical-Virtual-Cloud<br=
>
Widest out-of-the-box monitoring support with 50+ applications<br>
Performance metrics, stats and reports that give you Actionable Insights<br=
>
Deep dive visibility with transaction tracing using APM Insight.<br>
<a href=3D"http://ad.doubleclick.net/ddm/clk/290420510;117567292;y" target=
=3D"_blank">http://ad.doubleclick.net/ddm/clk/290420510;117567292;y</a><br>=
_______________________________________________<br>
Bitcoin-development mailing list<br>
<a href=3D"mailto:Bitcoin-development@lists.sourceforge.net">Bitcoin-develo=
pment@lists.sourceforge.net</a><br>
<a href=3D"https://lists.sourceforge.net/lists/listinfo/bitcoin-development=
" target=3D"_blank">https://lists.sourceforge.net/lists/listinfo/bitcoin-de=
velopment</a><br>
<br></blockquote></div><br></div></div>
--001a1140e85ebaf0f60515e7cd35--
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