[Page File Management] 재즈(함석명) 미션 제출합니다.

build.gradle

@@ -23,4 +23,4 @@ java {
 
 test {
     useJUnitPlatform()
-}
+}

src/main/java/database/BufferPool.java

@@ -0,0 +1,53 @@
+package database;
+
+import java.util.Map;
+
+public class BufferPool {
+
+    private static final int BUFFER_SIZE = 40;
+
+    private final Map<PageId, Page> bufferPool;
+    private final PageManager pageManager;
+
+    public BufferPool(PageManager pageManager) {
+        this.bufferPool = new LRUCache<>(BUFFER_SIZE, 0.75f, true, pageManager);
+        this.pageManager = pageManager;
+    }
+
+    public Page getPage(PageId pageId) {
+        Page page = bufferPool.computeIfAbsent(pageId, id -> pageManager.loadPage(pageId));
+        page.pin();
+        return page;
+    }
+
+    public void modifyPage(PageId pageId) {
+        Page page = getPage(pageId);
+        /*
+          ..modify..
+         */
+        page.setDirty(true);
+        page.unPin();
+    }
+
+    /**
+     * 플러시 리스트 플러시
+     */
+    public void flush() {
+        for (Map.Entry<PageId, Page> entry : bufferPool.entrySet()) {
+            Page page = entry.getValue();
+
+            if (!page.isPinned() && page.isDirty()) {
+                pageManager.savePage(entry.getKey(), page);
+                page.setDirty(false);
+            }
+        }
+    }
+
+    public Map<PageId, Page> getBufferPool() {
+        return bufferPool;
+    }
+
+    public PageManager getPageManager() {
+        return pageManager;
+    }
+}

src/main/java/database/FileManager.java

@@ -0,0 +1,62 @@
+package database;
+
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.io.RandomAccessFile;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+public class FileManager {
+
+    private static final String DIRECTORY_PATH = "data/files/";
+    private static final String FILE_EXTENSION = ".ibd";
+
+    public FileManager() {
+        createDirectory();
+    }
+
+    private void createDirectory() {
+        Path directory = Paths.get(DIRECTORY_PATH);
+        if (Files.notExists(directory)) {
+            try {
+                Files.createDirectories(directory);
+            } catch (IOException e) {
+                throw new RuntimeException(e);
+            }
+        }
+    }
+
+    public Page readPage(PageId pageId) {
+        Path filePath = Paths.get(DIRECTORY_PATH, pageId.getFileName() + FILE_EXTENSION);
+
+        try (RandomAccessFile file = new RandomAccessFile(filePath.toString(), "r")) {
+            long offset = (long) pageId.getPageNum() * Page.PAGE_SIZE;
+            file.seek(offset);
+
+            try (ObjectInputStream ois = new ObjectInputStream(new FileInputStream(file.getFD()))) {
+                return (Page) ois.readObject();
+            }
+        } catch (IOException | ClassNotFoundException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public void writePage(PageId pageId, Page page) {
+        Path filePath = Paths.get(DIRECTORY_PATH, pageId.getFileName() + FILE_EXTENSION);
+
+        try (RandomAccessFile file = new RandomAccessFile(filePath.toString(), "rw")) {
+            long offset = (long) pageId.getPageNum() * Page.PAGE_SIZE;
+            file.seek(offset);
+
+            try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(file.getFD()))) {
+                oos.writeObject(page);
+            }
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
+}

src/main/java/database/LRUCache.java

@@ -0,0 +1,34 @@
+package database;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+public class LRUCache<K, V> extends LinkedHashMap<K, V> {
+
+    private final int bufferSize;
+    private final PageManager pageManager;
+
+    public LRUCache(int initialCapacity, float loadFactor, boolean accessOrder, PageManager pageManager) {
+        super(initialCapacity, loadFactor, accessOrder);
+        this.pageManager = pageManager;
+        this.bufferSize = initialCapacity;
+    }
+
+    @Override
+    protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
+        boolean isBufferPoolOverCapacity = size() > bufferSize;
+        boolean isUnpinned = !((Page) eldest.getValue()).isPinned();
+
+        if (isBufferPoolOverCapacity && isUnpinned) {
+            flushIfDirty((PageId) eldest.getKey(), (Page) eldest.getValue());
+            return true;
+        }
+        return false;
+    }
+
+    private void flushIfDirty(PageId pageId, Page page) {
+        if (page.isDirty()) {
+            pageManager.savePage(pageId, page);
+        }
+    }
+}

src/main/java/database/Page.java

@@ -0,0 +1,92 @@
+package database;
+
+import java.io.Serializable;
+import java.util.ArrayList;
+import java.util.List;
+
+public class Page implements Serializable {
+
+    public static final int PAGE_SIZE = 16 * 1024;
+
+    private final PageHeader header;
+    private final List<Record> records;
+    private int freeSpace;
+    private int pinCount;
+
+    public Page(int pageNum, PageType pageType) {
+        this.header = new PageHeader(pageNum, pageType);
+        this.records = new ArrayList<>();
+        this.freeSpace = PAGE_SIZE - header.getHeaderSize();
+    }
+
+    public boolean addRecord(Record record) {
+        if (freeSpace >= record.getSize()) {
+            records.add(record);
+            freeSpace -= record.getSize();
+
+            header.incrementRecordCount();
+            header.setDirty(true);
+
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    public boolean deleteRecord(Record record) {
+        if (records.remove(record)) {
+            freeSpace += record.getSize();
+
+            header.setDirty(true);
+            header.decrementRecordCount();
+
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    public void pin() {
+        this.pinCount++;
+    }
+
+    public void unPin() {
+        this.pinCount--;
+    }
+
+    public boolean isPinned() {
+        return this.pinCount > 0;
+    }
+
+    public PageHeader getHeader() {
+        return header;
+    }
+
+    public List<Record> getRecords() {
+        return records;
+    }
+
+    public int getFreeSpace() {
+        return freeSpace;
+    }
+
+    public int getPinCount() {
+        return pinCount;
+    }
+
+    public void setDirty(boolean isDirty) {
+        header.setDirty(isDirty);
+    }
+
+    public boolean isDirty() {
+        return header.isDirty();
+    }
+
+    public PageType getPageType() {
+        return header.getPageType();
+    }
+
+    public int getPageNum() {
+        return header.getPageNum();
+    }
+}

src/main/java/database/PageHeader.java

@@ -0,0 +1,52 @@
+package database;
+
+import java.io.Serializable;
+
+public class PageHeader implements Serializable {
+
+    public static final int HEADER_SIZE = 13;
+
+    private final int pageNum;
+    private final PageType pageType;
+    private int recordCount;
+    private boolean isDirty;
+
+    public PageHeader(int pageNum, PageType pageType) {
+        this.pageNum = pageNum;
+        this.pageType = pageType;
+        this.recordCount = 0;
+        this.isDirty = false;
+    }
+
+    public void incrementRecordCount() {
+        this.recordCount++;
+    }
+
+    public void decrementRecordCount() {
+        this.recordCount--;
+    }
+
+    public void setDirty(boolean isDirty) {
+        this.isDirty = isDirty;
+    }
+
+    public int getPageNum() {
+        return pageNum;
+    }
+
+    public PageType getPageType() {
+        return pageType;
+    }
+
+    public int getRecordCount() {
+        return recordCount;
+    }
+
+    public boolean isDirty() {
+        return isDirty;
+    }
+
+    public int getHeaderSize() {
+        return HEADER_SIZE;
+    }
+}

src/main/java/database/PageId.java

@@ -0,0 +1,39 @@
+package database;
+
+import java.util.Objects;
+
+public class PageId {
+
+    private final String fileName;
+    private final int PageNum;
+
+    public PageId(String fileName, int pageNum) {
+        this.fileName = fileName;
+        this.PageNum = pageNum;
+    }
+
+    public String getFileName() {
+        return fileName;
+    }
+
+    public int getPageNum() {
+        return PageNum;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        PageId pageId = (PageId) o;
+        return PageNum == pageId.PageNum && Objects.equals(fileName, pageId.fileName);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(fileName, PageNum);
+    }
+}

src/main/java/database/PageManager.java

@@ -0,0 +1,18 @@
+package database;
+
+public class PageManager {
+
+    private final FileManager fileManager;
+
+    public PageManager(FileManager fileManager) {
+        this.fileManager = fileManager;
+    }
+
+    public Page loadPage(PageId pageId) {
+        return fileManager.readPage(pageId);
+    }
+
+    public void savePage(PageId pageId, Page page) {
+        fileManager.writePage(pageId, page);
+    }
+}

src/main/java/database/PageType.java

@@ -0,0 +1,8 @@
+package database;
+
+public enum PageType {
+
+    CLUSTERED_INDEX,
+    SECONDARY_INDEX,
+    UNDO_LOG;
+}

src/main/java/database/Record.java

@@ -0,0 +1,26 @@
+package database;
+
+import java.io.Serializable;
+
+public class Record implements Serializable {
+
+    private final int recordId;
+    private final byte[] data;
+
+    public Record(int recordId, byte[] data) {
+        this.recordId = recordId;
+        this.data = data;
+    }
+
+    public int getRecordId() {
+        return recordId;
+    }
+
+    public byte[] getData() {
+        return data;
+    }
+
+    public int getSize() {
+        return data.length;
+    }
+}