Perf/sorted batch

[asdacap]

• The write batch keys are sorted before putting into rocksdb. This improve throughput as rocksdb's skiplist has a fast path when keys are sorted in order.
• However, with path based layout, the size of the key doubled and the number of key doubled. This causes the overhead of sorting to be high enough that disabling it improve throughput.
• Additionally, with path based layout the keys are already partially ordered when inserted, making this sort not very useful.
• Disabling this optimization improve sync throughput for path based layout by about 20% to 25%.
• Perform exactly the same on hash based layout.

Changes

• Extract the sort logic to its own class.
• Enable it for TrieStore and receipt tx index.

Types of changes

What types of changes does your code introduce?

• Optimization

Testing

Requires testing

• Yes
• No

If yes, did you write tests?

• Yes
• No

[LukaszRozmej]

Isn't this something similar to: https://github.com/facebook/rocksdb/wiki/Write-Batch-With-Index ?

[asdacap]

Well, it does add the same functionality, but we're just interested in the sorting which increase throughput from about 0.9 to 1.25 mil keys per second. Already check if using the write batch with index automatically sort it, nope does not work.