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Author: gabotechs

benchmarks/src/util/memory.rs

@@ -24,6 +24,16 @@ static CACHE: LazyLock<DashMap<Key, Value>> = LazyLock::new(DashMap::default);
 
 /// Caches all the record batches in a global [CACHE] on the first run, and serves
 /// them from the cache in any subsequent run.
+/// The order of events looks like this:
+///   1. A first query is run.
+///   2. Data is not cached, so it is gathered from the underlying node.
+///   3. The cache is populated with the recently gathered data.
+///   4. A second query is run.
+///   5. The cache is hit, and data is returned from there.
+///
+/// The cache key includes the result of "explaining" the underlying node, so different
+/// nodes applying different filters under the same parquet files will be cached
+/// independently.
 #[derive(Debug, Clone)]
 pub struct InMemoryCacheExec {
     inner: Arc<dyn ExecutionPlan>,