Smaller disk usage on start

[dpc]

At Fedimint we test against esplora as one of the support backends. This makes it part of our integration tests and "devimint" dev environment, and we spin up and down such environment frequently.

On start devimint environment would have less than 200 empty regtest blocks, yet:

15:49:11 …esplora/regtest/newindex
> du -cksh *
286M    cache
286M    history
286M    txstore
858M    total

That's kind of a lot for indexing... practically nothing yet. Is this some pre-allocation or is it supposed to be this way? If it's a tunable could there be (is there) an option to minimize it? In our test env we're not really concerned about raw throughput.

[dpc]

https://github.com/Blockstream/electrs/blob/fd35014283c7d3a7a85c77b9fd647c9f09de12c9/src/new_index/db.rs#L92 I think.

I'm sorry. I think I should have opened this issue in that repo.