adriangb commented on code in PR #18192:
URL: https://github.com/apache/datafusion/pull/18192#discussion_r2446640086
##########
datafusion/proto/src/physical_plan/mod.rs:
##########
@@ -101,6 +102,42 @@ use datafusion_physical_plan::{ExecutionPlan,
InputOrderMode, PhysicalExpr, Wind
use prost::bytes::BufMut;
use prost::Message;
+/// Context for decoding physical expressions with caching support.
+///
+/// This struct wraps a `TaskContext` and maintains a cache of previously
deserialized
+/// physical expressions. The cache is keyed by the expression's ID (derived
from the
+/// Arc pointer during serialization), allowing duplicate expressions in a
plan to be
+/// deserialized only once.
+pub struct DecodeContext<'a> {
+ task_context: &'a TaskContext,
+ cache: Mutex<HashMap<u64, Arc<dyn PhysicalExpr>>>,
+}
+
+impl<'a> DecodeContext<'a> {
+ /// Create a new DecodeContext wrapping the given TaskContext.
+ pub fn new(task_context: &'a TaskContext) -> Self {
+ Self {
+ task_context,
+ cache: Mutex::new(HashMap::new()),
+ }
+ }
+
+ /// Get the underlying TaskContext reference.
+ pub fn task_context(&self) -> &'a TaskContext {
+ self.task_context
+ }
+
+ /// Attempt to retrieve a cached physical expression by its ID.
+ pub fn get_cached_expr(&self, id: u64) -> Option<Arc<dyn PhysicalExpr>> {
+ self.cache.lock().unwrap().get(&id).cloned()
+ }
+
+ /// Insert a physical expression into the cache with the given ID.
+ pub fn insert_cached_expr(&self, id: u64, expr: Arc<dyn PhysicalExpr>) {
+ self.cache.lock().unwrap().insert(id, expr);
+ }
Review Comment:
This does assume there's no other reader/writer so it's safe to check
`get()` then call `insert()` later and it's not possible that someone else
inserted before us.
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