transactions – What would stop some major company from blacklisting specific Bitcoins based on the “inputs” used and their “origins”?

I remember news about some exchange actually banning users based on some kind of “reputation score” on the inputs/coin parts they controlled/used, or got Bitcoin sent to them from. So even years and years back, they had this mapped out somehow.

Why can’t they do the same today? Aren’t they? If not, why? Why do they not take this obvious path to harassing and restricting people to only use Bitcoin in “approved” ways with “approved” people/entities?

Did they stop doing it for some reason? What stops them from doing this and thus locking out tons of people who have “dealt with undesirables”?

transactions – Confused about UTXO management and consolidation

UTXO management is not a singular goal. instead, it’s a method for balancing multiple priorities, including privacy, short-term fee savings and long-term fee savings.

Having lots of UTXOs is probably better for privacy, especially if they’re each in different addresses. But like you said, that will cost more in fees if you want to send your entire balance.

On the other hand, having all your bitcoin in one UTXO is probably not best for privacy or security.

Coin Control is a feature of some wallets, that allows users to directly control their UTXO management strategy. Wallets that don’t use coin control make those decisions for the user instead, so Coin Control is usually best for advanced users who know what UTXO management strategy they want.

mysql – Can two transactions lock rows in the same table in parallel?

I am trying to grasp the concept of MySQL locks and came across this section in the docs: https://dev.mysql.com/doc/refman/8.0/en/innodb-locks-set.html:

A locking read, an UPDATE, or a DELETE generally set record locks on every index record that is scanned in the processing of the SQL statement. It does not matter whether there are WHERE conditions in the statement that would exclude the row. InnoDB does not remember the exact WHERE condition, but only knows which index ranges were scanned.

That leads me to the conclusion that two transactions can never lock rows in the same table in parallel. Let me explain it on the following example:

Assume I have the following table:

CREATE TABLE t1 (id INT, PRIMARY KEY (id)) ENGINE = InnoDB;

Further, lets assume I have 7 rows inserted. This is the balanced tree of the primary key:

enter image description here

Now assume we lock row with id 3:

SELECT * FROM t1 WHERE id=3 FOR UPDATE

From the above paragrph

A locking read (..) set record locks on every index record that is scanned in the processing of the SQL statement.

I would guess that there is an exclusive lock on row 3,5,10. Is that right?

If that would be the case, then

SELECT * FROM t1 WHERE id=100 FOR UPDATE

would try to set an exclusive lock on row 10, because it scanned in the process to find 100. But that means, it has to wait for the other transaction to be finished.

This implies, any transaction that locks a row in table t1 will always first lock row with id 10. Thus, its not possible that two transactions lock two different rows in parallel.

My questions are:

  • Is that actually true?
  • How can I actually see the balanced index tree, so I can do some local testing?

Will nodes configured with a larger-than-default mempool automatically retransmit transactions that have been dropped from the default mempool?

If a transaction is sent and droppped from the default mempool before it is included in a block, but nodes with a larger-than-default mempool size exist that still have the transaction, will those nodes retransmit that transaction eventually?

This is a matter of policy, so different Bitcoin implementations may have different behaviors. I’m most curious about Bitcoin Core, since it’s very common, but if other node implementations differ, I’m curious about them too.

If such transactions aren’t retransmitted, I’m also curious why not, since it seems like such behavior might be useful.

coinbase.com – Unable to view coinbase transactions on blockchain.com

I’m trying to view some of the transactions I’ve made on coinbase on blockchain.com. I copied my btc wallet address from coinbase and searched it on blockchain.com — nothing showed up.

Why is this the case?

Per my understanding, given that coinbase stores my btc inside blockchain-powered wallets after I buy them, I should have been able to see all of my transactions.

unconfirmed transactions – How can I send less than 0.001 BTC from my Bitcoin Core Wallet

I recently managed to recover my wallet.dat and passphrase and have been trying to send the 0.00126913 BTC balance from my Bitcoin Core wallet into my Binance account, however the transactions stay unconfirmed for several days with no luck.

I’ve tried enabling ‘coin control features’ and sending 1-3 amounts at a time, however still no luck.

Is there anything I could do to increase the chance of my transactions being included into a block?