Function memo_query

crates/bench/src/sqlite.rs:226–254

Reduce latency of query formatting, for queries that are complicated to build.

(bench_name: BenchName, table_id: &str, generate_query: F)

#[inline(never)]
/// Reduce latency of query formatting, for queries that are complicated to build.
fn memo_query<F: FnOnce() -> String>(bench_name: BenchName, table_id: &str, generate_query: F) -> Arc<str> {
    // fast path
    let queries = QUERIES.read().unwrap();

    if let Some(bench_queries) = queries.get(&bench_name)
        && let Some(query) = bench_queries.get(table_id)
    {
        return query.clone();
    }

    // slow path
    drop(queries);
    let mut queries = QUERIES.write().unwrap();

    let bench_queries = if let Some(bench_queries) = queries.get_mut(&bench_name) {
        bench_queries
    } else {
        queries.insert(bench_name, HashMap::default());
        queries.get_mut(&bench_name).unwrap()
    };

    if let Some(query) = bench_queries.get(table_id) {
        query.clone()
    } else {
        let query = generate_query();
        bench_queries.insert(table_id.to_string(), (&query[..]).into());
        bench_queries[table_id].clone()
    }
}

lazy_static! {
    // bench_name -> table_id -> query.