Rocksdb experiment, watching consumed disk space

.gitignore

/target
/db
/Cargo.lock

build-rs.py

#!/usr/bin/env python
import os
import subprocess

rc = os.system('cargo build --release')
if rc != 0:
  exit(rc)

rc = subprocess.call('target/release/rocks.exe')
if rc != 0:
  exit(rc)

Cargo.toml

[package]
name = "rocks"
version = "0.1.0"
edition = "2021"

[[bin]]
name = "rocks"
path = "rocks.rs"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
glob = "0.3"
gstuff = {version = "0.7", features = ["nightly", "rdtsc"]}
rocksdb = {version = "0.17", default-features = false, features = ["zstd"]}

rocks.rs

use glob::glob;
use gstuff::rdtsc;
use rocksdb::{DB, DBCompressionType, Options};

fn size_on_disk() -> u64 {
    let mut size = 0;
    for file in glob (r"db/*") .unwrap() {
        if let Ok (file) = file {
            if let Ok (meta) = file.metadata() {
                if !meta.is_file() {continue}
                size += meta.len() as u64
            }
        }
    }
    size
}

fn main() {
    // https://docs.rs/rocksdb/latest/rocksdb/struct.Options.html
    // https://github.com/facebook/rocksdb/wiki/Universal-Compaction
    let mut opts = Options::default();
    opts.create_if_missing(true);
    opts.set_compression_type(DBCompressionType::Zstd);
    //opts.set_disable_auto_compactions(true);
    let db = DB::open(&opts, "db").unwrap();

    let mut cnt = 0_u64;
    let mut size = 0_u64;
    let mut last_id: Option<u64> = None;
    while cnt < 1_000_000_000 {
        let id = rdtsc();
        let write: [u8; 8] = unsafe { std::mem::transmute(id.to_be()) };

        let payload = vec![100; 10000];
        db.put(write, payload).unwrap();

        if let Some(last) = last_id {
            let last_key: [u8; 8] = unsafe { std::mem::transmute(last.to_be()) };
            db.delete(last_key).unwrap();
        }
        last_id = Some(id);

        if cnt % 1_000 == 0 {
            let cur_size = size_on_disk();
            if cnt % 1_000_000 == 0 {
                println!("{}", cur_size);
            }
            if cur_size < size {
                println!("db shrunk! From {} to {} MiB", size / 1024 / 1024, cur_size / 1024 / 1024);
            }
            size = cur_size;
        }
        cnt += 1;
    }
}