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From Shevek <she...@anarres.org>
Subject Cache patch for Peer.vm
Date Wed, 12 May 2004 13:43:21 GMT
I had a problem with requesting the same object twice and getting
different copies of the object. This causes inconsistency of data, data
loss, etc. I wrote a patch. It should guarantee that when you ask for the 
same object twice, you get the same object.

It would probably be good to have some sort of garbage collector on 
cleared SoftReferences. Usually walking over the cache every 1000 requests 
is adequate.

S.

-- 
Shevek                                    http://www.anarres.org/
I am the Borg.                         http://www.gothnicity.org/


--- Peer.vm.orig	2004-05-12 13:06:56.608192160 +0100
+++ Peer.vm	2004-05-12 14:27:28.962562632 +0100
@@ -1,5 +1,8 @@
 package ${package};
 
+import java.lang.ref.Reference;
+import java.lang.ref.SoftReference;
+
 import java.math.BigDecimal;
 import java.sql.Connection;
 import java.sql.SQLException;
@@ -8,6 +11,8 @@
 import java.util.Iterator;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.Map;
+import java.util.HashMap;
 
 import org.apache.torque.NoRowsException;
 import org.apache.torque.TooManyRowsException;
@@ -219,6 +224,74 @@
     #end
   #end
 
+
+
+
+
+  #if ($table.IdMethod.equals("none") || $table.PrimaryKey.size() == 0)
+        /* No caching possible without primary keys. */
+  #else
+    #set ($cacheDebug = 0)
+
+	/* Cache stuff. */
+
+	/** A map from ObjectKeys to weak object references. */
+	private static Map		objectCache = new HashMap();
+
+	private static ${table.JavaName} cacheGet(ObjectKey key) {
+		Reference	ref = (Reference)objectCache.get(key);
+		if (ref == null) {
+	#if ($cacheDebug != 0)
+			System.out.println("${table.JavaName}.cacheGet(" + key +
+							"): not in cache");
+	#end
+			return null;
+		}
+		$table.JavaName	ob = (${table.JavaName})ref.get();
+		if (ob == null) {
+	#if ($cacheDebug != 0)
+			System.out.println("${table.JavaName}.cacheGet(" + key +
+							"): cleared reference");
+	#end
+			cacheRemove(key);
+			return null;
+		}
+	#if ($cacheDebug != 0)
+		System.out.println("${table.JavaName}.cacheGet(" + key +
+						"): got object");
+	#end
+		return ob;
+	}
+
+	private static void cachePut(ObjectKey key, $table.JavaName ob) {
+	#if ($cacheDebug != 0)
+		System.out.println("${table.JavaName}.cachePut(" + key + ", " + ob.getId() + ")");
+	#end
+		Reference	ref = (Reference)objectCache.get(key);
+		if (ref != null)
+			if (ref.get() == ob)
+				return;
+		objectCache.put(key, new SoftReference(ob));
+	}
+
+	private static void cacheRemove(ObjectKey key) {
+	#if ($cacheDebug != 0)
+		System.out.println("${table.JavaName}.cacheRemove(" + key +")");
+	#end
+		objectCache.remove(key);
+	}
+
+  #end
+
+
+
+
+
+
+
+
+
+
     /**
      * Method to do inserts.
      *
@@ -336,6 +409,12 @@
         {
             $table.JavaName obj = ($table.JavaName) cls.newInstance();
             ${table.JavaName}Peer.populateObject(row, offset, obj);
+			ObjectKey	key = obj.getPrimaryKey();
+			$table.JavaName	cached = cacheGet(key);
+			if (cached != null)
+				return cached;
+			else
+				cachePut(key, obj);
   #if ($addSaveMethod)
                 obj.setModified(false);
   #end
@@ -794,6 +873,7 @@
         doInsert(buildCriteria(obj));
   #else
         obj.setPrimaryKey(doInsert(buildCriteria(obj)));
+		cachePut(obj.getPrimaryKey(), obj);
   #end
         obj.setNew(false);
         obj.setModified(false);
@@ -817,6 +897,9 @@
      */
     public static void doDelete($table.JavaName obj) throws TorqueException
     {
+  #if (! $table.IdMethod.equals("none") && $table.PrimaryKey.size() > 0)
+		cacheRemove(obj.getPrimaryKey());
+  #end
         doDelete(buildCriteria(obj));
     }
 
@@ -837,6 +920,7 @@
         doInsert(buildCriteria(obj), con);
   #else
         obj.setPrimaryKey(doInsert(buildCriteria(obj), con));
+		cachePut(obj.getPrimaryKey(), obj);
   #end
         obj.setNew(false);
         obj.setModified(false);
@@ -872,6 +956,9 @@
     public static void doDelete($table.JavaName obj, Connection con)
         throws TorqueException
     {
+  #if (! $table.IdMethod.equals("none") && $table.PrimaryKey.size() > 0)
+		cacheRemove(obj.getPrimaryKey());
+  #end
         doDelete(buildCriteria(obj), con);
     }
 
@@ -884,6 +971,7 @@
      */
     public static void doDelete(ObjectKey pk) throws TorqueException
     {
+		cacheRemove(pk);
         $basePrefix${table.JavaName}Peer
            .doDelete(pk, (Connection) null);
     }
@@ -901,6 +989,7 @@
     public static void doDelete(ObjectKey pk, Connection con)
         throws TorqueException
     {
+		cacheRemove(pk);
         doDelete(buildCriteria(pk), con);
     }
 
@@ -1003,6 +1092,10 @@
     public static $table.JavaName ${retrieveMethod}(ObjectKey pk, Connection con)
         throws TorqueException, NoRowsException, TooManyRowsException
     {
+		$table.JavaName	obj = cacheGet(pk);
+		if (obj != null)
+			return obj;
+
         Criteria criteria = buildCriteria(pk);
         List v = doSelect(criteria, con);
         if (v.size() == 0)

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