[GitHub] [pinot] kirkrodrigues commented on a diff in pull request #11006: Add CLPDecodeRewriter to make it easier to call clpDecode with a column-group name rather than the individual columns.

["kirkrodrigues (via GitHub)" <gi...@apache.org>]

kirkrodrigues commented on code in PR #11006:
URL: https://github.com/apache/pinot/pull/11006#discussion_r1248344244


##########
pinot-common/src/main/java/org/apache/pinot/sql/parsers/rewriter/CLPDecodeRewriter.java:
##########
@@ -0,0 +1,176 @@
+/**
+ * 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.pinot.sql.parsers.rewriter;
+
+import java.util.List;
+import javax.annotation.Nullable;
+import org.apache.pinot.common.function.TransformFunctionType;
+import org.apache.pinot.common.request.Expression;
+import org.apache.pinot.common.request.ExpressionType;
+import org.apache.pinot.common.request.Function;
+import org.apache.pinot.common.request.Identifier;
+import org.apache.pinot.common.request.Literal;
+import org.apache.pinot.common.request.PinotQuery;
+import org.apache.pinot.sql.parsers.SqlCompilationException;
+
+
+/**
+ * Query rewriter to rewrite clpDecode so that users can pass in the name of a CLP-encoded column group instead of the
+ * names of all the columns in the group.
+ * <p>
+ * Usage:
+ * <pre>
+ *   clpDecode("columnGroupName"[, defaultValue])
+ * </pre>
+ * which will be rewritten to:
+ * <pre>
+ *   clpDecode("columnGroupName_logtype", "columnGroupName_dictionaryVars", "columnGroupName_encodedVars"[,
+ *   defaultValue])
+ * </pre>
+ * The "defaultValue" is optional. See
+ * {@link org.apache.pinot.core.operator.transform.function.CLPDecodeTransformFunction} for its description.
+ * <p>
+ * Sample queries:
+ * <pre>
+ *   SELECT clpDecode("message") FROM table
+ *   SELECT clpDecode("message", 'null') FROM table
+ * </pre>
+ * See {@link org.apache.pinot.core.operator.transform.function.CLPDecodeTransformFunction} for details about the
+ * underlying clpDecode transformer.
+ */
+public class CLPDecodeRewriter implements QueryRewriter {
+  public static final String LOGTYPE_COLUMN_SUFFIX = "_logtype";
+  public static final String DICTIONARY_VARS_COLUMN_SUFFIX = "_dictionaryVars";
+  public static final String ENCODED_VARS_COLUMN_SUFFIX = "_encodedVars";
+
+  private static final String _CLPDECODE_LOWERCASE_TRANSFORM_NAME =
+      TransformFunctionType.CLPDECODE.getName().toLowerCase();
+
+  @Override
+  public PinotQuery rewrite(PinotQuery pinotQuery) {
+    List<Expression> selectExpressions = pinotQuery.getSelectList();
+    if (null != selectExpressions) {
+      for (Expression e : selectExpressions) {
+        tryRewritingExpression(e);
+      }
+    }
+    List<Expression> groupByExpressions = pinotQuery.getGroupByList();
+    if (null != groupByExpressions) {
+      for (Expression e : groupByExpressions) {
+        tryRewritingExpression(e);
+      }
+    }
+    List<Expression> orderByExpressions = pinotQuery.getOrderByList();
+    if (null != orderByExpressions) {
+      for (Expression e : orderByExpressions) {
+        tryRewritingExpression(e);
+      }
+    }
+    tryRewritingExpression(pinotQuery.getFilterExpression());
+    tryRewritingExpression(pinotQuery.getHavingExpression());
+    return pinotQuery;
+  }
+
+  /**
+   * Rewrites any instances of clpDecode in the given expression
+   * @param expression Expression which may contain instances of clpDecode
+   */
+  private void tryRewritingExpression(Expression expression) {
+    if (null == expression) {
+      return;
+    }
+    Function function = expression.getFunctionCall();
+    if (null == function) {
+      return;
+    }
+
+    String functionName = function.getOperator();
+    if (functionName.equals(_CLPDECODE_LOWERCASE_TRANSFORM_NAME)) {
+      rewriteCLPDecodeFunction(expression);
+    } else {
+      // Function isn't a CLP function that needs rewriting, but the arguments might be, so we recursively process them.
+      for (Expression op : function.getOperands()) {
+        tryRewritingExpression(op);
+      }
+    }
+  }
+
+  /**
+   * Rewrites the given instance of clpDecode as described in the class docstring

Review Comment:
   Ah, I think it's a [general term](https://en.wikipedia.org/wiki/Docstring) for API documentation comments, but the more specific term in Java is a Javadoc, so switched to that.



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