z_importwallet takes an unreasonable amount of time

[Greg Slepak]

Describe the issue

Please provide a general summary of the issue you're experiencing

Can you reliably reproduce the issue?

If so, please list the steps to reproduce below:

1. Import a previously exported wallet using z_importwallet

Expected behaviour

The wallet should import. Ideally in under 1 minute.

Actual behaviour + errors

At the current rate, which has significantly slowed down, it will take 133 days to for the "Still rescanning" thing to finish. It may in fact take longer, because the rate has been slowing down. In the meantime, the zcash node has become completely unusable. This is on fast hardware that has an SSD. It does not seem acceptable for a wallet import to render the node unusable for 1/3 of a year (or longer). What do I do now?

EDIT: thankfully it didn't take 133 days, apparently there is section that goes by very slowly. It did take more than 48 hours though, and for some people that might be way too long.

The version of Zcash you were using:

v5.6.1

Machine specs:

• OS name + version: Fedora 38 (Server Edition)
• CPU: 4 core 2.7GHz Intel
• RAM: 16GB
• Disk size: ?
• Disk Type (HD/SDD): SSD
• Linux kernel version (uname -a): 6.4.6-200.fc38.x86_64
• Compiler version (gcc --version): not relevant (using container)
• Linker version (ld -v): not relevant (using container)
• Assembler version (as --version): not relevant (using container)

[Greg Slepak]

Shutting down the node and bringing it back up doesn't fix it. The rescan continues. Does this mean that both exporting wallets and importing wallets is pointless because it will destroy the node?

Seems related to #6052. Is there any way to stop the rescan?