[GitHub] [uima-ruta] reckart commented on a change in pull request #9: [UIMA-6231] introducing new static cache for reusing Pattern objects in REGEXP and RegExpRule

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reckart commented on a change in pull request #9:
URL: https://github.com/apache/uima-ruta/pull/9#discussion_r426876898



##########
File path: ruta-core/src/main/java/org/apache/uima/ruta/RutaPatternCache.java
##########
@@ -0,0 +1,61 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ * 
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.uima.ruta;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.regex.Pattern;
+
+/**
+ * Cache and centralize creation of regex patterns in order to reuse them in different language
+ * elements
+ *
+ */
+public class RutaPatternCache {
+
+  protected static final Map<String, Pattern> CACHE = new HashMap<>();

Review comment:
       I think it would be better to create a PatternCacheKey class here in which the pattern and eventual flags are modelled explicitly instead of constructing a String key.

##########
File path: ruta-core/src/main/java/org/apache/uima/ruta/RutaPatternCache.java
##########
@@ -0,0 +1,61 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ * 
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.uima.ruta;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.regex.Pattern;
+
+/**
+ * Cache and centralize creation of regex patterns in order to reuse them in different language
+ * elements
+ *
+ */
+public class RutaPatternCache {
+
+  protected static final Map<String, Pattern> CACHE = new HashMap<>();

Review comment:
       Using a static cache without any strategy for removing cached data is a potential memory leak. Unless we have a good reason not to do so, I would suggest using the Caffeine library where we can define different types of expunging strategies (time based, load based, size-based). Or some other type of cache scoping would be required. One possibility could be to attach the cache to a UIMA context available through an UimaContextHolder. In that case, the context could be used as a key in a WeakHashMap causing cached patterns to be garbage collected when the context goes away.




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