From 405555278dbe6e44653c6b35c04209572376afa7 Mon Sep 17 00:00:00 2001
From: hns <hannesw@gmail.com>
Date: Fri, 9 Mar 2001 16:05:31 +0000
Subject: [PATCH] Implemented caching of null nodes in getNode (Node, String,
Relation). A singleton nullNode is used to cache Node objects in the
application cache if they don't exist.
---
src/helma/objectmodel/db/NodeManager.java | 28 +++++++++++++++++++++--
1 file changed, 26 insertions(+), 2 deletions(-)
diff --git a/src/helma/objectmodel/db/NodeManager.java b/src/helma/objectmodel/db/NodeManager.java
index eb11405f..5d32ae2b 100644
--- a/src/helma/objectmodel/db/NodeManager.java
+++ b/src/helma/objectmodel/db/NodeManager.java
@@ -38,6 +38,9 @@ public final class NodeManager {
// a wrapper that catches some Exceptions while accessing this NM
public final WrappedNodeManager safe;
+ // an instance of Node that's used to cache null values
+ private Node nullNode;
+
public NodeManager (Application app, String dbHome, Properties props) throws DbException {
this.app = app;
int cacheSize = Integer.parseInt (props.getProperty ("cachesize", "1000"));
@@ -47,6 +50,7 @@ public final class NodeManager {
app.logEvent ("set up node cache ("+cacheSize+")");
safe = new WrappedNodeManager (this);
+ nullNode = new Node ("nullNode", "nullNode", null, safe);
// get the initial id generator value
String idb = props.getProperty ("idBaseValue");
@@ -222,15 +226,35 @@ public final class NodeManager {
// check if node is already in cache with primary key
Node oldnode = (Node) cache.put (primKey, node);
// no need to check for oldnode != node because we fetched a new node from db
- if (oldnode != null && oldnode.getState () != Node.INVALID) {
+ if (oldnode != null && oldnode != nullNode && oldnode.getState () != Node.INVALID) {
cache.put (primKey, oldnode);
if (!keyIsPrimary)
cache.put (key, oldnode);
node = oldnode;
- } else if (!keyIsPrimary) // cache node with secondary key
+ } else if (!keyIsPrimary) {
+ // cache node with secondary key
cache.put (key, node);
+ }
} // synchronized
+ } else {
+ // node fetched from db is null, cache result using nullNode
+ synchronized (cache) {
+ Node oldnode = (Node) cache.put (key, nullNode);
+ // for the rare case that some other thread created the node in the meantime
+ if (oldnode != null && oldnode != nullNode && oldnode.getState () != Node.INVALID) {
+ Key primKey = oldnode.getKey ();
+ boolean keyIsPrimary = primKey.equals (key);
+ cache.put (oldnode.getKey (), oldnode);
+ if (!keyIsPrimary)
+ cache.put (key, oldnode);
+ node = oldnode;
+ } else {
+ return null;
+ }
+ }
}
+ } else if (node == nullNode) {
+ return null;
} else {
// update primary key in cache to keep it from being flushed, see above
if (!rel.usesPrimaryKey ()) {