prepared: wrap result metadata with ArcSwap

In the following commit, the result metadata will be updated during reprepare. We make use of `ArcSwap`, which is a mechanism used for shared data which is rarely updated.
scylladb · Feb 7, 2024 · a9a2a6c · a9a2a6c
1 parent c001c80
commit a9a2a6c
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Showing 3 changed files with 8 additions and 7 deletions.
diff --git a/scylla/src/statement/prepared_statement.rs b/scylla/src/statement/prepared_statement.rs
@@ -1,3 +1,4 @@
+use arc_swap::ArcSwap;
 use bytes::{Bytes, BytesMut};
 use scylla_cql::errors::{BadQuery, QueryError};
 use scylla_cql::frame::types::RawValue;
@@ -37,7 +38,7 @@ pub struct PreparedStatement {
 #[derive(Debug)]
 struct PreparedStatementSharedData {
     metadata: PreparedMetadata,
-    result_metadata: ResultMetadata,
+    result_metadata: ArcSwap<ResultMetadata>,
     statement: String,
 }
 
@@ -69,7 +70,7 @@ impl PreparedStatement {
             id,
             shared: Arc::new(PreparedStatementSharedData {
                 metadata,
-                result_metadata,
+                result_metadata: ArcSwap::from_pointee(result_metadata),
                 statement,
             }),
             prepare_tracing_ids: Vec::new(),
@@ -310,8 +311,8 @@ impl PreparedStatement {
     }
 
     /// Access metadata about the result of prepared statement returned by the database
-    pub fn get_result_metadata(&self) -> &ResultMetadata {
-        &self.shared.result_metadata
+    pub fn get_result_metadata(&self) -> Arc<ResultMetadata> {
+        self.shared.result_metadata.load_full()
     }
 
     /// Get the name of the partitioner used for this statement.

diff --git a/scylla/src/transport/caching_session.rs b/scylla/src/transport/caching_session.rs
@@ -197,7 +197,7 @@ where
                 id: prepared.get_id().clone(),
                 is_confirmed_lwt: prepared.is_confirmed_lwt(),
                 metadata: prepared.get_prepared_metadata().clone(),
-                result_metadata: prepared.get_result_metadata().clone(),
+                result_metadata: prepared.get_result_metadata().as_ref().clone(),
                 partitioner_name: prepared.get_partitioner_name().clone(),
             };
             self.cache.insert(query_contents, raw);

diff --git a/scylla/src/transport/connection.rs b/scylla/src/transport/connection.rs
@@ -720,7 +720,7 @@ impl Connection {
                 &execute_frame,
                 true,
                 prepared_statement.config.tracing,
-                cached_metadata,
+                cached_metadata.as_deref(),
             )
             .await?;
 
@@ -737,7 +737,7 @@ impl Connection {
                     &execute_frame,
                     true,
                     prepared_statement.config.tracing,
-                    cached_metadata,
+                    cached_metadata.as_deref(),
                 )
                 .await
             }