RESET PREPARED: clear the cache with default config, never reuse statement names

pgdog/src/admin/parser.rs

@@ -255,6 +255,12 @@ mod tests {
         assert!(matches!(result, Ok(ParseResult::ResetQueryCache(_))));
     }
 
+    #[test]
+    fn parses_reset_prepared_command() {
+        let result = Parser::parse("RESET PREPARED");
+        assert!(matches!(result, Ok(ParseResult::ResetPrepared(_))));
+    }
+
     #[test]
     fn rejects_unknown_admin_command() {
         let result = Parser::parse("FOO BAR");

pgdog/src/admin/reset_prepared.rs

@@ -1,5 +1,4 @@
 //! RESET PREPARED.
-use crate::config::config;
 use crate::frontend::prepared_statements::PreparedStatements;
 
 use super::prelude::*;
@@ -17,10 +16,40 @@ impl Command for ResetPrepared {
     }
 
     async fn execute(&self) -> Result<Vec<Message>, Error> {
-        let config = config();
-        PreparedStatements::global()
-            .write()
-            .close_unused(config.config.general.prepared_statements_limit);
+        // Deliberately not the configured limit: RESET clears everything
+        // not in use regardless of it.
+        PreparedStatements::global().write().close_unused(0);
         Ok(vec![])
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::net::messages::Parse;
+
+    #[tokio::test]
+    async fn reset_prepared_clears_released_statements() {
+        let held;
+        let released;
+        {
+            let global = PreparedStatements::global();
+            let mut cache = global.write();
+            held = cache.insert(&Parse::named("s", "SELECT 'rp_held'")).1;
+            released = cache.insert(&Parse::named("s", "SELECT 'rp_released'")).1;
+            cache.close(&released);
+        }
+
+        // Default prepared_statements_limit is unlimited;
+        // the command must clear released statements anyway.
+        ResetPrepared.execute().await.unwrap();
+
+        let global = PreparedStatements::global();
+        let cache = global.read();
+        assert!(
+            cache.parse(&released).is_none(),
+            "released statement cleared"
+        );
+        assert!(cache.parse(&held).is_some(), "statement in use survives");
+    }
+}

pgdog/src/frontend/prepared_statements/global_cache.rs

@@ -232,7 +232,9 @@ impl GlobalCache {
         }
     }
 
-    /// Clear the global cache.
+    /// Clear the global cache. Test-only: rolling the name counter back
+    /// would reuse global statement names.
+    #[cfg(test)]
     pub fn reset(&mut self) {
         self.statements.clear();
         self.names.clear();
@@ -310,14 +312,10 @@ impl GlobalCache {
         }
     }
 
-    /// Close all unused statements exceeding capacity.
+    /// Close unused statements until the cache is down to `capacity` entries;
+    /// `0` removes everything not in use. Statements in use stay, and global
+    /// names are never reused.
     pub fn close_unused(&mut self, capacity: usize) -> usize {
-        if capacity == 0 {
-            let removed = self.len();
-            self.reset();
-            return removed;
-        }
-
         let over = self.len().saturating_sub(capacity);
         let remove = self.unused.iter().take(over).copied().collect::<Vec<_>>();
 
@@ -362,6 +360,23 @@ impl GlobalCache {
 mod test {
     use super::*;
 
+    #[test]
+    fn test_close_unused_zero_keeps_in_use_and_counter() {
+        let mut cache = GlobalCache::default();
+
+        let (_, held) = cache.insert(&Parse::named("s", "SELECT 'held'"));
+        let (_, released) = cache.insert(&Parse::named("s", "SELECT 'released'"));
+        cache.close(&released);
+
+        assert_eq!(cache.close_unused(0), 1, "only the released statement goes");
+        assert!(cache.parse(&held).is_some(), "statements in use survive");
+        assert!(cache.parse(&released).is_none());
+
+        // A reused name could hand a server connection a different query.
+        let (_, next) = cache.insert(&Parse::named("s", "SELECT 'next'"));
+        assert_eq!(next, "__pgdog_3", "global names are never reused");
+    }
+
     #[test]
     fn test_prep_stmt_cache_close() {
         let mut cache = GlobalCache::default();