[GitHub] [lucene-solr] zhaih commented on a change in pull request #1613: LUCENE-8574 Cache ExpressionFunctionValues

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

zhaih commented on a change in pull request #1613:
URL: https://github.com/apache/lucene-solr/pull/1613#discussion_r448525027



##########
File path: lucene/expressions/src/java/org/apache/lucene/expressions/CachingExpressionValueSource.java
##########
@@ -0,0 +1,70 @@
+/*
+ * 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.lucene.expressions;
+
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.apache.lucene.index.LeafReaderContext;
+import org.apache.lucene.search.DoubleValues;
+import org.apache.lucene.search.DoubleValuesSource;
+
+final class CachingExpressionValueSource extends ExpressionValueSource {
+
+  CachingExpressionValueSource(Bindings bindings, Expression expression) {
+    super(bindings, expression);
+  }
+
+  CachingExpressionValueSource(DoubleValuesSource[] variables, Expression expression, boolean needsScores) {
+    super(variables, expression, needsScores);
+  }
+
+  public CachingExpressionValueSource(ExpressionValueSource expressionValueSource) {
+    super(expressionValueSource.variables, expressionValueSource.expression, expressionValueSource.needsScores);
+  }
+
+  @Override
+  public DoubleValues getValues(LeafReaderContext readerContext, DoubleValues scores) throws IOException {
+    return getValuesWithCache(readerContext, scores, new HashMap<>());
+  }
+
+  public DoubleValues getValuesWithCache(LeafReaderContext readerContext, DoubleValues scores,
+                                                  Map<String, DoubleValues> valuesCache) throws IOException {
+    DoubleValues[] externalValues = new DoubleValues[expression.variables.length];
+
+    for (int i = 0; i < variables.length; ++i) {
+      String externalName = expression.variables[i];
+      DoubleValues values = valuesCache.get(externalName);
+      if (values == null) {
+        if (variables[i] instanceof CachingExpressionValueSource) {
+          values = ((CachingExpressionValueSource)variables[i]).getValuesWithCache(readerContext, scores, valuesCache);
+        } else {
+          values = variables[i].getValues(readerContext, scores);
+        }
+        if (values == null) {
+          throw new RuntimeException("Internal error. External (" + externalName + ") does not exist.");

Review comment:
       Yeah I think this error is happened because of a dependent variable was not bound. The message is actually inherited from `ExpressionValueSource#getValue` so I believe we'd better not change it or change both?




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