Refactored calls to 'mysql_stmt_close' into function holding preparation of 'MYSQL_STMT*' parameter #3525

include/gen_utils.h

@@ -229,6 +229,23 @@ inline unsigned long long realtime_time() {
   clock_gettime(CLOCK_REALTIME, &ts);
   return (((unsigned long long) ts.tv_sec) * 1000000) + (ts.tv_nsec / 1000);
 }
+
+/**
+ * @brief ProxySQL replacement function for 'mysql_stmt_close'. Closes a
+ *   MYSQL_STMT avoiding any blocking commands that are sent by default
+ *   'mysql_stmt_close'.
+ *
+ *   NOTE: This function is not safe, caller must check that the supplied
+ *   argument is not NULL.
+ *
+ * @param mysql_stmt An already initialized 'MYSQL_STMT'. Caller must ensure
+ *   that the supplied argument is not NULL.
+ *
+ * @return The result of calling 'mysql_stmt_close' function over the internally
+ *   modified 'MYSQL_STMT'.
+ */
+my_bool proxy_mysql_stmt_close(MYSQL_STMT* mysql_stmt);
+
 #endif /* __GEN_FUNCTIONS */
 
 bool Proxy_file_exists(const char *);

lib/MySQL_PreparedStatement.cpp

@@ -691,12 +691,7 @@ MySQL_STMTs_local_v14::~MySQL_STMTs_local_v14() {
 			it != global_stmt_to_backend_stmt.end(); ++it) {
 			uint64_t global_stmt_id = it->first;
 			MYSQL_STMT *stmt = it->second;
-			if (stmt->mysql) {
-				stmt->mysql->stmts =
-				    list_delete(stmt->mysql->stmts, &stmt->list);
-			}
-			stmt->mysql = NULL;
-			mysql_stmt_close(stmt);
+			proxy_mysql_stmt_close(stmt);
 			GloMyStmt->ref_count_server(global_stmt_id, -1);
 		}
 	}

lib/gen_utils.cpp

@@ -219,3 +219,15 @@ bool Proxy_file_regular(const char *path) {
 		if (sb.st_mode & S_IFREG) return true;
 	return false;
 }
+
+my_bool proxy_mysql_stmt_close(MYSQL_STMT* stmt) {
+	// Clean internal structures for 'stmt->mysql->stmts'.
+	if (stmt->mysql) {
+		stmt->mysql->stmts =
+			list_delete(stmt->mysql->stmts, &stmt->list);
+	}
+	// Nullify 'mysql' field to avoid sending a blocking command to the server.
+	stmt->mysql = NULL;
+	// Perform the regular close operation.
+	return mysql_stmt_close(stmt);
+}

lib/mysql_connection.cpp

@@ -2151,7 +2151,7 @@ void MySQL_Connection::async_free_result() {
 			// initialized, it must be freed. For more context see #3525.
 			if (this->async_state_machine == ASYNC_STMT_PREPARE_FAILED) {
 				if (query.stmt != NULL) {
-					mysql_stmt_close(query.stmt);
+					proxy_mysql_stmt_close(query.stmt);
 				}
 			}
 			query.stmt=NULL;