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https://issues.apache.org/jira/browse/METAMODEL-224?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15093973#comment-15093973
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ASF GitHub Bot commented on METAMODEL-224:
------------------------------------------
Github user kaspersorensen commented on a diff in the pull request:
https://github.com/apache/metamodel/pull/85#discussion_r49461420
--- Diff: core/src/main/java/org/apache/metamodel/query/ConcatFunction.java
---
@@ -0,0 +1,65 @@
+/**
+ * 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) {
+ if (parameters.length == 0) {
+ throw new IllegalArgumentException("Expecting some parameters
to CONCAT function");
+ }
+ StringBuilder strBuilder = new StringBuilder();
+ for (Object parameter: parameters) {
+ final Object valueToConcat;
+ if (parameter instanceof SelectItem) {
+ valueToConcat = row.getValue((SelectItem) parameter);
+ } else if (parameter instanceof Column) {
+ valueToConcat = row.getValue((Column) parameter);
+ } else {
+ valueToConcat = parameter;
+ }
+ strBuilder.append(valueToConcat.toString());
+ }
+ return strBuilder;
+ }
+
+ @Override
+ public ColumnType getExpectedColumnType(ColumnType type) {
+ // the column type cannot be inferred so null is returned
+ return null;
--- End diff --
I would say that it should return ColumnType.STRING since it's always going
to be a String.
> Support CONCAT function
> -----------------------
>
> Key: METAMODEL-224
> URL: https://issues.apache.org/jira/browse/METAMODEL-224
> Project: Apache MetaModel
> Issue Type: New Feature
> Reporter: Alberto
> Priority: Minor
>
> As we now support scalar functions it would be great to add support for a
> CONCAT function that allow us to concatenate and append strings to the query
> results.
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