Page eviction

src/main/java/me/doubledutch/pikadb/Column.java

@@ -3,6 +3,10 @@
 import java.util.*;
 import java.io.*;
 
+import me.doubledutch.pikadb.page.Page;
+import me.doubledutch.pikadb.page.PageFile;
+
+
 public class Column{
 	private PageFile pageFile;
 	public int rootId;

src/main/java/me/doubledutch/pikadb/Soup.java

@@ -2,6 +2,10 @@
 
 import java.io.*;
 import java.util.*;
+
+import me.doubledutch.pikadb.page.Page;
+import me.doubledutch.pikadb.page.PageFile;
+
 import org.json.*;
 
 public class Soup{

src/main/java/me/doubledutch/pikadb/Test.java

@@ -2,6 +2,10 @@
 
 import java.io.*;
 import java.util.*;
+
+import me.doubledutch.pikadb.page.Page;
+import me.doubledutch.pikadb.page.PageFile;
+
 import org.json.*;
 
 public class Test{
@@ -229,6 +233,17 @@ public static void main(String args[]){
 			obj=soup.scan(RECORDS/2);
 			// System.out.println(obj);
 
+			int totalHit, totalMiss;
+			totalHit = totalMiss = 0;
+			for (Map.Entry<Integer,Page> entry : f.pageMap.entrySet()){
+				Page page=entry.getValue();
+				totalHit += page.getCacheHits();
+				totalMiss += page.getCacheMisses();
+				//if (page.cacheMiss > 0 || page.cacheHit > 0){
+				//	System.out.println("Page "+entry.getKey()+": "+page.cacheHit+" hits, "+page.cacheMiss+" misses");
+				//}
+			}
+			System.out.println(" -- Cache hit ratio: "+(float)totalHit/(totalMiss+totalHit));
 			f.close();
 
 			/*

src/main/java/me/doubledutch/pikadb/Variant.java

@@ -1,7 +1,11 @@
 package me.doubledutch.pikadb;
 
 import java.io.*;
+
+import me.doubledutch.pikadb.page.Page;
+
 import org.json.*;
+
 import java.util.*;
 
 public abstract class Variant implements Comparable<Variant>{

src/main/java/me/doubledutch/pikadb/WriteAheadLog.java

@@ -1,5 +1,7 @@
 package me.doubledutch.pikadb;
 
+import me.doubledutch.pikadb.page.PageDiff;
+
 public class WriteAheadLog{
 	public WriteAheadLog(String filename){
 

src/main/java/me/doubledutch/pikadb/page/LRUPageCache.java

@@ -0,0 +1,35 @@
+package me.doubledutch.pikadb.page;
+
+import java.util.ArrayDeque;
+import java.util.Deque;
+import java.util.Map;
+
+class LRUPageCache implements PageCache{
+	private int size;
+	private Map<Integer, Page> pageMap;
+	private Deque<Integer> pageCache;
+
+	public LRUPageCache(Map<Integer, Page> map, int size){
+		this.size=size;
+		this.pageMap=map;
+		this.pageCache=new ArrayDeque<Integer>();
+	}
+
+	public boolean Set(int id){
+		if (!pageMap.containsKey(id)){
+			return false;
+		}
+		boolean cached=false;
+		if (pageCache.contains(id)){
+			pageCache.remove(id);
+			cached=true;
+		}
+		pageCache.addFirst(id);
+		if (pageCache.size() > size){
+			Integer evictID=pageCache.removeLast();
+			Page evict=pageMap.get(evictID);
+			evict.unloadRawData();
+		}
+		return cached;
+	}
+}	

src/main/java/me/doubledutch/pikadb/page/NoopPageCache.java

@@ -0,0 +1,8 @@
+package me.doubledutch.pikadb.page;
+
+
+class NoopPageCache implements PageCache{
+	public boolean Set(int id) {
+		return false;
+	}
+}

src/main/java/me/doubledutch/pikadb/Page.java → src/main/java/me/doubledutch/pikadb/page/Page.java

@@ -1,8 +1,10 @@
-package me.doubledutch.pikadb;
+package me.doubledutch.pikadb.page;
 
 import java.util.*;
 import java.io.*;
 
+import me.doubledutch.pikadb.WriteAheadLog;
+
 public class Page{
 	public static int UNSORTED=0;
 	public static int SORTED=1;
@@ -29,6 +31,8 @@ public class Page{
 
 	private List<PageDiff> diffList=new LinkedList<PageDiff>();
 
+	private int cacheMiss, cacheHit;
+
 	public Page(int id,long offset,RandomAccessFile pageFile,PageFile pageHandler) throws IOException{
 		this.id=id;
 		this.offset=offset;
@@ -74,9 +78,12 @@ protected void unloadRawData(){
 	private void loadRawData() throws IOException{
 		if(rawData==null){
 			pageHandler.trimPageSet(id);
+			cacheMiss++;
 			rawData=new byte[PAYLOAD];
 			pageFile.seek(offset+HEADER);
 			pageFile.readFully(rawData);
+		} else {
+			cacheHit++;
 		}
 	}
 
@@ -181,4 +188,12 @@ public void appendData(byte[] data){
 		dirty=true;
 		// System.out.println("currentFill: "+id+" "+currentFill+" "+data.length);
 	}
+
+	public int getCacheHits() {
+		return cacheHit;
+	}
+
+	public int getCacheMisses() {
+		return cacheMiss;
+	}
 }

src/main/java/me/doubledutch/pikadb/page/PageCache.java

@@ -0,0 +1,10 @@
+package me.doubledutch.pikadb.page;
+
+interface PageCache{
+	/**
+	 * Sets an item in the cache
+	 * @param id id of cached item
+	 * @return whether or not item is cached
+	 */
+	boolean Set(int id);
+}

src/main/java/me/doubledutch/pikadb/PageDiff.java → src/main/java/me/doubledutch/pikadb/page/PageDiff.java

@@ -1,4 +1,4 @@
-package me.doubledutch.pikadb;
+package me.doubledutch.pikadb.page;
 
 public class PageDiff{
 	private int offset;

src/main/java/me/doubledutch/pikadb/PageFile.java → src/main/java/me/doubledutch/pikadb/page/PageFile.java

@@ -1,15 +1,20 @@
-package me.doubledutch.pikadb;
+package me.doubledutch.pikadb.page;
 
 import java.io.*;
 import java.nio.channels.*;
 import java.util.*;
 
+import me.doubledutch.pikadb.Column;
+import me.doubledutch.pikadb.WriteAheadLog;
+
 public class PageFile{
-	private Map<Integer,Page> pageMap=new HashMap<Integer,Page>();
+	public Map<Integer,Page> pageMap=new HashMap<Integer,Page>();
 	private RandomAccessFile pageFile;
 	private FileChannel pageFileChannel;
 	private String filename;
 	private WriteAheadLog wal=null;
+	private PageCache cache;
+	private static int CACHE_SIZE = 500;
 
 	public PageFile(String filename) throws IOException{
 		this.filename=filename;
@@ -22,15 +27,15 @@ public PageFile(String filename) throws IOException{
 			ftest.delete();
 			wal=null;
 		}
+		this.cache=new SLRUPageCache(pageMap, CACHE_SIZE);
 	}
 
 	private void recoverTransaction(){
 		// Replay everything in the write ahead log
 	}
 
-
-	private void trimPageSet(int id){
-
+	protected void trimPageSet(int id){
+		cache.Set(id);
 	}
 
 	public Page getPage(int id) throws IOException{
@@ -71,7 +76,7 @@ public void saveChanges(boolean sort) throws IOException{
 				page.flatten();
 				Column.sort(page);
 			}
-		 	page.commitChanges(wal);
+			page.commitChanges(wal);
 		}
 		wal.closeTransaction();
 		// Write to page file

src/main/java/me/doubledutch/pikadb/page/SLRUPageCache.java

@@ -0,0 +1,49 @@
+package me.doubledutch.pikadb.page;
+
+import java.util.ArrayDeque;
+import java.util.Deque;
+import java.util.Map;
+
+class SLRUPageCache implements PageCache{
+	private int size;
+	private Map<Integer, Page> pageMap;
+	private Deque<Integer> l1, l2;
+
+	public SLRUPageCache(Map<Integer, Page> map, int size){
+		this.size=size;
+		this.pageMap=map;
+		this.l1=new ArrayDeque<Integer>();
+		this.l2=new ArrayDeque<Integer>();
+	}
+
+	public boolean Set(int id){
+		if (!pageMap.containsKey(id)){
+			return false;
+		}
+		// If the page exists in L1, move it to L2
+		// If L2 at size, move end to back of L1
+		if (l1.contains(id)){
+			l1.remove(id);
+			l2.addLast(id);
+			if (l2.size() > size){
+				l1.addFirst(l2.removeLast());
+			}
+			return true;
+		}
+		// If page exists in L2, move to L2 front
+		if (l2.contains(id)){
+			l2.remove(id);
+			l2.addFirst(id);
+			return true;
+		}
+		// Put at front of L1 cache
+		l1.addFirst(id);
+		// If L1 size is at maximum, evict last page
+		if (l1.size() > size){
+			Integer evictID=l1.removeLast();
+			Page evict=pageMap.get(evictID);
+			evict.unloadRawData();
+		}
+		return false;
+	}
+}