huaxingao commented on code in PR #6252: URL: https://github.com/apache/iceberg/pull/6252#discussion_r1037692461
########## api/src/main/java/org/apache/iceberg/expressions/AggregateUtil.java: ########## @@ -0,0 +1,142 @@ +/* + * 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.iceberg.expressions; + +import java.util.List; +import org.apache.iceberg.Table; +import org.apache.iceberg.exceptions.ValidationException; +import org.apache.iceberg.types.Type; +import org.apache.iceberg.types.Types; + +/** Aggregate utility methods. */ +public class AggregateUtil { + private AggregateUtil() {} + + /** + * Create a NestedField for this Aggregate Expression. This NestedField is used to build the + * pushed down aggregate schema. + * + * <p>e.g. SELECT COUNT(*), MAX(col1), MIN(col1), MAX(col2), MIN(col3) FROM table; + * + * <p>Suppose the table schema is Schema( Types.NestedField.required(1, "col1", + * Types.IntegerType.get()), Types.NestedField.required(2, "col2", Types.StringType.get()), + * Types.NestedField.required(3, "col3", Types.StringType.get()) ); + * + * <p>The returned NestedField for the aggregates are Types.NestedField.required(1, COUNT(*), + * Types.LongType.get()) Types.NestedField.required(2, MAX(col1), Types.IntegerType.get()) + * Types.NestedField.required(3, MIN(col1), Types.IntegerType.get()) Types.NestedField.required(4, + * MAX(col2), Types.StringType.get()) Types.NestedField.required(5, MIN(col3), + * Types.StringType.get()) + */ + public static Types.NestedField getAggregateNestedField(Expression expr, int index) { + return ExpressionVisitors.visit(expr, new AggregateNestedFieldVisitor(index)); + } + + /** + * Returns the column name this aggregate function is on. e.g. SELECT Max(col3) FROM table; This + * method returns col3 + */ + public static String getAggregateColumnName(Expression expr) { + return ExpressionVisitors.visit(expr, new AggregateColumnNameVisitor()); + } + + /** + * Returns the data type of this Aggregate Expression. The data type for COUNT is always Long. The + * data type for MAX and MIX are the same as the data type of the column this aggregate is applied + * on. + */ + public static Type getAggregateType(Expression expr) { + return ExpressionVisitors.visit(expr, new AggregateTypeVisitor()); + } + + /** + * Returns the index of this Aggregate column in table schema. e.g. SELECT Max(col3) FROM table; + * Suppose the table has columns (col1, col2, col3), this method returns 2. + */ + public static int columnIndexInTableSchema(Expression expr, Table table, boolean caseSensitive) { + return ExpressionVisitors.visit(expr, new AggregateColumnIndexVisitor(table, caseSensitive)); + } + + private static class AggregateNestedFieldVisitor Review Comment: I removed the visitors. I am not sure if I should implement this [eval](https://github.com/apache/iceberg/blob/898df4695e87dc615a631892a1529259ca61c10b/api/src/main/java/org/apache/iceberg/expressions/BoundAggregate.java#L31). It seems easier to get the values directly. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: issues-unsubscr...@iceberg.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@iceberg.apache.org For additional commands, e-mail: issues-h...@iceberg.apache.org
