[+]增加索引模块 (#13)

* 增加错误基类、简单的记录接口

* 增加.gitignore

* 完成记录的mock

* 增加记录接口的简易单元测试

* 引入Slf4j、log4j、jbbp外部库

* [+]add table mock and unit test

* 增加Travis配置

* fix: transform java14 to java11

* 更新Gradle配置以允许Scan ToS

* 删除冗余Travis配置

* README增加Travis Badge

* 增加UTF-8 gradle配置

* 对于数据项管理的mock和测试部分

* 修改测试用例的文件名

* index mock

* 增加事务的Mock

* testPage

* index mock plus test

* 对于数据项管理的mock和测试部分的修改

* testPage1.01

* dataitem模块修改建议

* 修正编码风格

* 对于数据项管理的mock和测试部分

* 对于数据项管理的mock和测试部分

* Index审计、修改建议

* 增加JBBP的使用示例

* page模块审计、修改建议

* 删除table模块，更改record模块

* recovery模块审计

* transaction模块审计

* 对于日志恢复的接口和测试

* 完善事务模块接口

* testPage1.02

* testPage1.03

* 复审recovery,tx

* 格式化代码

* 更新README

* 修改异常名称

* 修正编译失败

* 表创建、表头解析以及页头解析

* 索引审计修改

* RumbaseException增加错误原因

* 完善事务模块接口，增加事务模块测试用例

* 修正事务接口

* 修正事务接口

* 测试用例修改

* B+树索引，没有flush，没有锁，用synchronized并发也有小问题

* 改进测试用例

* synchronized修改

* 加了pin和unpin,听从lmx建议取消了root页作为成员

* 加了flush,完善了pin和unpin,添加了相对更为复杂的并发测试，由于mock的限制，flush和pin功能并不能得到良好的保证

* 修正、改进单元测试

* 缩小单元测试规模，解决文件冲突

Co-authored-by: Kevin Axel Manjaro <kevinaxel@163.com>
Co-authored-by: Kevin Axel <41867249+KveinAxel@users.noreply.github.com>
Co-authored-by: xiaoxineryi <529086017@qq.com>
Co-authored-by: DctorWei1314 <61504793+DctorWei1314@users.noreply.github.com>
Co-authored-by: Criterionist <1229089076@qq.com>
Co-authored-by: XuanLaoYee <1115810634@qq.com>

src/main/java/net/kaaass/rumbase/index/Index.java

@@ -1,9 +1,17 @@
 package net.kaaass.rumbase.index;
 
+import net.kaaass.rumbase.index.btree.BPlusTreeIndex;
 import net.kaaass.rumbase.index.exception.IndexAlreadyExistException;
 import net.kaaass.rumbase.index.exception.IndexNotFoundException;
 import net.kaaass.rumbase.index.mock.MockBtreeIndex;
+import net.kaaass.rumbase.page.Page;
+import net.kaaass.rumbase.page.PageManager;
+import net.kaaass.rumbase.page.PageStorage;
+import net.kaaass.rumbase.page.exception.FileException;
 
+import javax.swing.*;
+import java.io.File;
+import java.io.IOException;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
@@ -23,10 +31,16 @@ public interface Index extends Iterable<Pair> {
      * @throws IndexNotFoundException
      */
     static Index getIndex(String indexFileName) throws IndexNotFoundException {
-        if (MockBtreeIndex.MOCK_BTREE_INDEX_MAP.get(indexFileName) == null) {
-            throw new IndexNotFoundException(1);
-        }
-        return MockBtreeIndex.MOCK_BTREE_INDEX_MAP.get(indexFileName);
+            if (BPlusTreeIndex.B_PLUS_TREE_INDEX_MAP.get(indexFileName) != null) {
+                return BPlusTreeIndex.B_PLUS_TREE_INDEX_MAP.get(indexFileName);
+            } else {
+                BPlusTreeIndex bPlusTreeIndex = new BPlusTreeIndex(indexFileName);
+                if (!bPlusTreeIndex.isIndexedFile()) {
+                    throw new IndexNotFoundException(1);
+                }
+                BPlusTreeIndex.B_PLUS_TREE_INDEX_MAP.put(indexFileName, bPlusTreeIndex);
+                return bPlusTreeIndex;
+            }
     }
 
     /**
@@ -36,7 +50,7 @@ static Index getIndex(String indexFileName) throws IndexNotFoundException {
      * @return
      */
     static boolean exists(String indexFileName) {
-        return MockBtreeIndex.MOCK_BTREE_INDEX_MAP.get(indexFileName) != null;
+        return new File(indexFileName).exists();
     }
 
     /**
@@ -47,12 +61,13 @@ static boolean exists(String indexFileName) {
      * @throws IndexAlreadyExistException
      */
     static Index createEmptyIndex(String indexFileName) throws IndexAlreadyExistException {
-        if (MockBtreeIndex.MOCK_BTREE_INDEX_MAP.get(indexFileName) == null) {
-            MockBtreeIndex.MOCK_BTREE_INDEX_MAP.put(indexFileName, new MockBtreeIndex());
-        } else {
+        BPlusTreeIndex bPlusTreeIndex = new BPlusTreeIndex(indexFileName);
+        if (bPlusTreeIndex.isIndexedFile()) {
             throw new IndexAlreadyExistException(1);
         }
-        return MockBtreeIndex.MOCK_BTREE_INDEX_MAP.get(indexFileName);
+        bPlusTreeIndex.initPage();
+        BPlusTreeIndex.B_PLUS_TREE_INDEX_MAP.put(indexFileName, bPlusTreeIndex);
+        return bPlusTreeIndex;
     }
 
     /**