Using cursor causes OOM mybatis#2812

src/test/java/org/apache/ibatis/submitted/cursor_cache_oom/CursorOomTest.java

@@ -0,0 +1,114 @@
+/*
+ *    Copyright 2009-2023 the original author or authors.
+ *
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
+ *
+ *       https://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+package org.apache.ibatis.submitted.cursor_cache_oom;
+
+import java.io.IOException;
+import java.io.Reader;
+import java.lang.reflect.Field;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.ibatis.BaseDataTest;
+import org.apache.ibatis.cache.CacheKey;
+import org.apache.ibatis.cursor.Cursor;
+import org.apache.ibatis.cursor.defaults.DefaultCursor;
+import org.apache.ibatis.executor.resultset.DefaultResultSetHandler;
+import org.apache.ibatis.io.Resources;
+import org.apache.ibatis.session.SqlSession;
+import org.apache.ibatis.session.SqlSessionFactory;
+import org.apache.ibatis.session.SqlSessionFactoryBuilder;
+import org.apache.ibatis.session.defaults.DefaultSqlSession;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+@SuppressWarnings("ALL")
+class CursorOomTest {
+
+    private static SqlSessionFactory sqlSessionFactory;
+
+    @BeforeAll
+    static void setUp() throws Exception {
+        // create an SqlSessionFactory
+        try (Reader reader = Resources.getResourceAsReader(
+                "org/apache/ibatis/submitted/cursor_cache_oom/mybatis-config.xml")) {
+            sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
+        }
+
+        // populate in-memory database
+        BaseDataTest.runScript(
+                sqlSessionFactory.getConfiguration().getEnvironment().getDataSource(),
+                "org/apache/ibatis/submitted/cursor_cache_oom/CreateDB.sql"
+        );
+    }
+
+    private static Map<CacheKey, Object> getNestedResultObjects(Cursor<User> users) throws IllegalAccessException,
+            NoSuchFieldException {
+        DefaultCursor<User> defaultCursor = (DefaultCursor<User>) users;
+        Field resultSetHandlerField = DefaultCursor.class.getDeclaredField("resultSetHandler");
+        resultSetHandlerField.setAccessible(true);
+        DefaultResultSetHandler defaultResultSetHandler =
+                (DefaultResultSetHandler) resultSetHandlerField
+                        .get(defaultCursor);
+        Field nestedResultObjectsField = DefaultResultSetHandler.class.getDeclaredField("nestedResultObjects");
+        nestedResultObjectsField.setAccessible(true);
+        return (Map<CacheKey, Object>) nestedResultObjectsField
+                .get(defaultResultSetHandler);
+    }
+
+    private static List<Cursor<?>> getCursors(SqlSession sqlSession)
+            throws NoSuchFieldException, IllegalAccessException {
+        DefaultSqlSession session = (DefaultSqlSession) sqlSession;
+        Field cursorListField = DefaultSqlSession.class.getDeclaredField("cursorList");
+        cursorListField.setAccessible(true);
+        List<Cursor<?>> cursorList =
+                (List<Cursor<?>>) cursorListField.get(session);
+        return cursorList;
+    }
+
+    @Test
+    void shouldNotCacheAllDataForWholeSessionWhileUsingCursor() throws IOException, NoSuchFieldException,
+            IllegalAccessException {
+        try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
+            Mapper mapper = sqlSession.getMapper(Mapper.class);
+            try (Cursor<User> users = mapper.fetchUsers()) {
+                for (User user : users) {
+                    consumeUser(user);
+                }
+                Map nestedResultObjects = getNestedResultObjects(users);
+
+                Assertions.assertFalse(nestedResultObjects.isEmpty());
+
+                // does not pass now
+                // will be great, if cursor will use constant memory instead of linear one
+//                Assertions.assertTrue(nestedResultObjects.size() <= 2);
+            }
+
+            List<Cursor<?>> cursorList = getCursors(sqlSession);
+
+            // expect that either reference to the cursor itselfis gone or cursor does not contains all the fetched data
+            // the most preferrable way will be not to cache data, when the row is already processed (see commented
+            // line above)
+            Assertions.assertTrue(
+                    cursorList.isEmpty() || getNestedResultObjects((Cursor<User>) cursorList.get(0)).isEmpty()
+            );
+        }
+    }
+
+    private void consumeUser(User user) {
+        // do nothing
+    }
+}

src/test/java/org/apache/ibatis/submitted/cursor_cache_oom/Friend.java

@@ -0,0 +1,29 @@
+/*
+ *    Copyright 2009-2022 the original author or authors.
+ *
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
+ *
+ *       https://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+package org.apache.ibatis.submitted.cursor_cache_oom;
+
+public class Friend {
+
+  private String name;
+
+  public String getName() {
+    return name;
+  }
+
+  public void setName(String name) {
+    this.name = name;
+  }
+}

src/test/java/org/apache/ibatis/submitted/cursor_cache_oom/Mapper.java

@@ -0,0 +1,27 @@
+/*
+ *    Copyright 2009-2022 the original author or authors.
+ *
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
+ *
+ *       https://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+package org.apache.ibatis.submitted.cursor_cache_oom;
+
+import org.apache.ibatis.cursor.Cursor;
+
+public interface Mapper {
+
+  User getUser(Integer id);
+
+  void insertUser(User user);
+
+  Cursor<User> fetchUsers();
+}

src/test/java/org/apache/ibatis/submitted/cursor_cache_oom/User.java

@@ -0,0 +1,47 @@
+/*
+ *    Copyright 2009-2022 the original author or authors.
+ *
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
+ *
+ *       https://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+package org.apache.ibatis.submitted.cursor_cache_oom;
+
+public class User {
+
+    private Integer id;
+    private String name;
+    private Friend friend;
+
+    public Integer getId() {
+        return id;
+    }
+
+    public void setId(Integer id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public Friend getFriend() {
+        return friend;
+    }
+
+    public void setFriend(Friend friend) {
+        this.friend = friend;
+    }
+}

src/test/resources/org/apache/ibatis/submitted/cursor_cache_oom/CreateDB.sql

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+--
+--    Copyright 2009-2022 the original author or authors.
+--
+--    Licensed under the Apache License, Version 2.0 (the "License");
+--    you may not use this file except in compliance with the License.
+--    You may obtain a copy of the License at
+--
+--       https://www.apache.org/licenses/LICENSE-2.0
+--
+--    Unless required by applicable law or agreed to in writing, software
+--    distributed under the License is distributed on an "AS IS" BASIS,
+--    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+--    See the License for the specific language governing permissions and
+--    limitations under the License.
+--
+
+drop table users if exists;
+
+create table users (
+  id int,
+  name varchar(20),
+  friend_id int
+);
+
+create sequence IF NOT EXISTS cursor_cache_oom START WITH 1 INCREMENT BY 1;
+
+insert into users (id, name, friend_id)
+SELECT nr, 'test' + nr, mod((nr + 1), 10000) + 1
+from unnest(sequence_array(1, 10000, 1)) as i(nr);

src/test/resources/org/apache/ibatis/submitted/cursor_cache_oom/Mapper.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+       Copyright 2009-2022 the original author or authors.
+
+       Licensed under the Apache License, Version 2.0 (the "License");
+       you may not use this file except in compliance with the License.
+       You may obtain a copy of the License at
+
+          https://www.apache.org/licenses/LICENSE-2.0
+
+       Unless required by applicable law or agreed to in writing, software
+       distributed under the License is distributed on an "AS IS" BASIS,
+       WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+       See the License for the specific language governing permissions and
+       limitations under the License.
+
+-->
+<!DOCTYPE mapper
+    PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
+    "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
+
+<mapper namespace="org.apache.ibatis.submitted.cursor_cache_oom.Mapper">
+
+    <select id="getUser" resultType="org.apache.ibatis.submitted.cursor_cache_oom.User">
+        select * from users where id = #{id}
+    </select>
+
+    <insert id="insertUser">
+        insert into users values(#{id}, #{name})
+    </insert>
+
+    <select id="fetchUsers" resultMap="User">
+        select u.id as id, u.name as name, f.name as friend_name
+        from users as u
+        left join users as f on u.friend_id = f.id
+    </select>
+
+    <resultMap id="User" type="org.apache.ibatis.submitted.cursor_cache_oom.User">
+        <id property="id" column="id"/>
+        <result property="name" column="name"/>
+        <association property="friend" resultMap="Friend"/>
+    </resultMap>
+
+    <resultMap id="Friend" type="org.apache.ibatis.submitted.cursor_cache_oom.Friend">
+        <result property="name" column="friend_name"/>
+    </resultMap>
+</mapper>

src/test/resources/org/apache/ibatis/submitted/cursor_cache_oom/mybatis-config.xml

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+<?xml version="1.0" encoding="UTF-8" ?>
+<!--
+
+       Copyright 2009-2022 the original author or authors.
+
+       Licensed under the Apache License, Version 2.0 (the "License");
+       you may not use this file except in compliance with the License.
+       You may obtain a copy of the License at
+
+          https://www.apache.org/licenses/LICENSE-2.0
+
+       Unless required by applicable law or agreed to in writing, software
+       distributed under the License is distributed on an "AS IS" BASIS,
+       WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+       See the License for the specific language governing permissions and
+       limitations under the License.
+
+-->
+<!DOCTYPE configuration
+    PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
+    "https://mybatis.org/dtd/mybatis-3-config.dtd">
+
+<configuration>
+
+    <environments default="development">
+        <environment id="development">
+            <transactionManager type="JDBC">
+                <property name="" value="" />
+            </transactionManager>
+            <dataSource type="UNPOOLED">
+                <property name="driver" value="org.hsqldb.jdbcDriver" />
+                <property name="url" value="jdbc:hsqldb:mem:basetest" />
+                <property name="username" value="sa" />
+            </dataSource>
+        </environment>
+    </environments>
+
+    <mappers>
+        <mapper class="org.apache.ibatis.submitted.cursor_cache_oom.Mapper" />
+    </mappers>
+
+</configuration>