[INLONG-11229][SDK] Transform Support ELT Function (apache#11248)

inlong-sdk/transform-sdk/src/main/java/org/apache/inlong/sdk/transform/process/function/EltFunction.java

@@ -0,0 +1,67 @@
+/*
+ * 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.inlong.sdk.transform.process.function;
+
+import org.apache.inlong.sdk.transform.decode.SourceData;
+import org.apache.inlong.sdk.transform.process.Context;
+import org.apache.inlong.sdk.transform.process.operator.OperatorTools;
+import org.apache.inlong.sdk.transform.process.parser.ValueParser;
+
+import net.sf.jsqlparser.expression.Expression;
+import net.sf.jsqlparser.expression.Function;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * EltFunction -> elt(index, expr[, exprs]*)
+ * description:
+ * - Returns the index-th expression.
+ * - index must be an integer between 1 and the number of expressions.
+ * - Returns NULL if index is NULL or out of range.
+ */
+@TransformFunction(names = {"elt"})
+public class EltFunction implements ValueParser {
+
+    private ValueParser indexParser;
+    private List<ValueParser> exprParsers;
+
+    public EltFunction(Function expr) {
+        List<Expression> expressions = expr.getParameters().getExpressions();
+        indexParser = OperatorTools.buildParser(expressions.get(0));
+        exprParsers = new ArrayList<>();
+        for (int i = 1; i < expressions.size(); i++) {
+            exprParsers.add(OperatorTools.buildParser(expressions.get(i)));
+        }
+    }
+
+    @Override
+    public Object parse(SourceData sourceData, int rowIndex, Context context) {
+        Object indexObject = indexParser.parse(sourceData, rowIndex, context);
+        if (indexObject == null) {
+            return null;
+        }
+
+        int index = OperatorTools.parseBigDecimal(indexObject).intValue();
+        if (index < 1 || index > exprParsers.size()) {
+            return null;
+        }
+
+        return exprParsers.get(index - 1).parse(sourceData, rowIndex, context);
+    }
+}

inlong-sdk/transform-sdk/src/test/java/org/apache/inlong/sdk/transform/process/function/string/TestEltFunction.java

@@ -0,0 +1,85 @@
+/*
+ * 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.inlong.sdk.transform.process.function.string;
+
+import org.apache.inlong.sdk.transform.decode.SourceDecoderFactory;
+import org.apache.inlong.sdk.transform.encode.SinkEncoderFactory;
+import org.apache.inlong.sdk.transform.pojo.TransformConfig;
+import org.apache.inlong.sdk.transform.process.TransformProcessor;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.HashMap;
+import java.util.List;
+
+public class TestEltFunction extends AbstractFunctionStringTestBase {
+
+    @Test
+    public void testEltFunction() throws Exception {
+        String transformSql = null, data = null;
+        TransformConfig config = null;
+        TransformProcessor<String, String> processor = null;
+        List<String> output = null;
+
+        // case1: elt(2, 'a', 'b', 'c')
+        transformSql = "select elt(numeric1, string1, string2, string3) from source";
+        config = new TransformConfig(transformSql);
+        processor = TransformProcessor
+                .create(config, SourceDecoderFactory.createCsvDecoder(csvSource),
+                        SinkEncoderFactory.createKvEncoder(kvSink));
+        data = "a|b|c|2";
+        output = processor.transform(data, new HashMap<>());
+        Assert.assertEquals(1, output.size());
+        Assert.assertEquals("result=b", output.get(0));
+
+        // case2: elt(4, 'a', 'b', 'c') - index out of range
+        data = "a|b|c|4";
+        output = processor.transform(data, new HashMap<>());
+        Assert.assertEquals(1, output.size());
+        Assert.assertEquals("result=", output.get(0));
+
+        // case3: elt(null, 'a', 'b', 'c') - index is null
+        data = "a|b|c|";
+        output = processor.transform(data, new HashMap<>());
+        Assert.assertEquals(1, output.size());
+        Assert.assertEquals("result=", output.get(0));
+
+        // case4: elt(2, 1, 2, 3) - expressions are numbers
+        transformSql = "select elt(numeric1, numeric1, numeric2, numeric3) from source";
+        config = new TransformConfig(transformSql);
+        processor = TransformProcessor
+                .create(config, SourceDecoderFactory.createCsvDecoder(csvSource),
+                        SinkEncoderFactory.createKvEncoder(kvSink));
+        data = "a|b|c|2|2|3";
+        output = processor.transform(data, new HashMap<>());
+        Assert.assertEquals(1, output.size());
+        Assert.assertEquals("result=2", output.get(0));
+
+        // case5: elt(1, 'a', 2, 'c') - mixed types
+        transformSql = "select elt(numeric1, string1, numeric1, string2) from source";
+        config = new TransformConfig(transformSql);
+        processor = TransformProcessor
+                .create(config, SourceDecoderFactory.createCsvDecoder(csvSource),
+                        SinkEncoderFactory.createKvEncoder(kvSink));
+        data = "a|2|c|1";
+        output = processor.transform(data, new HashMap<>());
+        Assert.assertEquals(1, output.size());
+        Assert.assertEquals("result=a", output.get(0));
+    }
+}