Github user albertostratio commented on a diff in the pull request:
https://github.com/apache/metamodel/pull/85#discussion_r49311167
--- Diff: core/src/main/java/org/apache/metamodel/query/ConcatFunction.java
---
@@ -0,0 +1,79 @@
+/**
+ * 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.metamodel.query;
+
+import org.apache.metamodel.data.Row;
+import org.apache.metamodel.schema.Column;
+import org.apache.metamodel.schema.ColumnType;
+import org.apache.metamodel.util.CollectionUtils;
+import org.apache.metamodel.util.Predicate;
+
+import java.util.List;
+
+/**
+ * Represents a function that concatenates values.
+ */
+public final class ConcatFunction extends DefaultScalarFunction {
+
+ @Override
+ public Object evaluate(Row row, Object[] parameters, SelectItem
operandItem) {
+ SelectItem[] selectItems = row.getSelectItems();
+ if (parameters.length == 0) {
+ throw new IllegalArgumentException("Expecting some parameters
to CONCAT function");
+ }
+ StringBuilder strBuilder = new StringBuilder();
+ for (Object parameter: parameters) {
+ String parameterAsString = parameter.toString();
--- End diff --
In this function the parameters are not only Strings they are either
Columns (for the column parameters) or Strings (for the literals). Then in the
method depending of whether the param is a Column or a literal we append the
value get from the row or just the literal.
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