[GitHub] ottobackwards commented on a change in pull request #3277: NIFI-5801: Improved performance of Expression Language evaluation by …

[GitBox <gi...@apache.org>]

ottobackwards commented on a change in pull request #3277: NIFI-5801: Improved performance of Expression Language evaluation by …
URL: https://github.com/apache/nifi/pull/3277#discussion_r252051248
 
 

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 File path: nifi-commons/nifi-expression-language/src/main/java/org/apache/nifi/attribute/expression/language/MultiValueLookup.java
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+/*
+ * 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.nifi.attribute.expression.language;
+
+import org.apache.nifi.flowfile.FlowFile;
+import org.apache.nifi.registry.VariableDescriptor;
+import org.apache.nifi.registry.VariableRegistry;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+public class MultiValueLookup implements ValueLookup {
+    final List<Map<String, String>> maps = new ArrayList<>();
+    final VariableRegistry registry;
+
+    /**
+     * Constructs a ValueLookup where values are looked up first based any
+     * provided additional maps, then flowfile properties, then flowfile
+     * attributes, then based on the provided variable registry. The lookup is
+     * immutable and operations which attempt to alter state will throw
+     * UnsupportedOperationException
+     *
 
 Review comment:
   Is this class thread safe?

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