hanyuzheng7 commented on code in PR #23173: URL: https://github.com/apache/flink/pull/23173#discussion_r1492749138
########## flink-table/flink-table-runtime/src/main/java/org/apache/flink/table/runtime/functions/scalar/ArrayExceptFunction.java: ########## @@ -0,0 +1,161 @@ +/* + * 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.flink.table.runtime.functions.scalar; + +import org.apache.flink.annotation.Internal; +import org.apache.flink.table.api.DataTypes; +import org.apache.flink.table.api.Expressions; +import org.apache.flink.table.data.ArrayData; +import org.apache.flink.table.data.GenericArrayData; +import org.apache.flink.table.functions.BuiltInFunctionDefinitions; +import org.apache.flink.table.functions.FunctionContext; +import org.apache.flink.table.functions.SpecializedFunction; +import org.apache.flink.table.types.CollectionDataType; +import org.apache.flink.table.types.DataType; +import org.apache.flink.util.FlinkRuntimeException; + +import javax.annotation.Nullable; + +import java.lang.invoke.MethodHandle; +import java.util.ArrayList; +import java.util.HashSet; +import java.util.List; +import java.util.Set; + +import static org.apache.flink.table.api.Expressions.$; + +/** Implementation of {@link BuiltInFunctionDefinitions#ARRAY_EXCEPT}. */ +@Internal +public class ArrayExceptFunction extends BuiltInScalarFunction { + private final ArrayData.ElementGetter elementGetter; + private final SpecializedFunction.ExpressionEvaluator hashcodeEvaluator; + private final SpecializedFunction.ExpressionEvaluator equalityEvaluator; + private transient MethodHandle hashcodeHandle; + + private transient MethodHandle equalityHandle; + + public ArrayExceptFunction(SpecializedFunction.SpecializedContext context) { + super(BuiltInFunctionDefinitions.ARRAY_EXCEPT, context); + final DataType dataType = + ((CollectionDataType) context.getCallContext().getArgumentDataTypes().get(0)) + .getElementDataType() + .toInternal(); + elementGetter = ArrayData.createElementGetter(dataType.toInternal().getLogicalType()); + hashcodeEvaluator = + context.createEvaluator( + Expressions.call("$HASHCODE$1", $("element1")), + DataTypes.INT(), + DataTypes.FIELD("element1", dataType.notNull().toInternal())); + equalityEvaluator = + context.createEvaluator( + $("element1").isEqual($("element2")), + DataTypes.BOOLEAN(), + DataTypes.FIELD("element1", dataType.notNull().toInternal()), + DataTypes.FIELD("element2", dataType.notNull().toInternal())); + } + + @Override + public void open(FunctionContext context) throws Exception { + hashcodeHandle = hashcodeEvaluator.open(context); + equalityHandle = equalityEvaluator.open(context); + } + + public @Nullable ArrayData eval(ArrayData arrayOne, ArrayData arrayTwo) { + try { + if (arrayOne == null) { + return null; + } + + List<Object> list = new ArrayList<>(); + Set<ObjectContainer> seen = new HashSet<>(); + + boolean isNullPresentInArrayTwo = false; + if (arrayTwo != null) { + for (int pos = 0; pos < arrayTwo.size(); pos++) { + final Object element = elementGetter.getElementOrNull(arrayTwo, pos); + if (element == null) { + isNullPresentInArrayTwo = true; + } else { + ObjectContainer objectContainer = new ObjectContainer(element); + seen.add(objectContainer); + } + } + } + boolean isNullPresentInArrayOne = false; + for (int pos = 0; pos < arrayOne.size(); pos++) { + final Object element = elementGetter.getElementOrNull(arrayOne, pos); + if (element == null) { + isNullPresentInArrayOne = true; + } else { + ObjectContainer objectContainer = new ObjectContainer(element); + if (!seen.contains(objectContainer)) { + seen.add(objectContainer); + list.add(element); + } + } + } + if (!isNullPresentInArrayTwo && isNullPresentInArrayOne) { + list.add(null); + } Review Comment: Ok I have already done some research, here is what I find in others DBs. For snowflake: [](https://docs.snowflake.com/en/sql-reference/functions/array_except) ``` Returns This function returns an ARRAY that contains the elements from source_array that are not in array_of_elements_to_exclude. If no elements remain after excluding the elements in array_of_elements_to_exclude from source_array, the function returns an empty ARRAY. If one or both arguments are NULL, the function returns NULL. The order of the values within the returned array is unspecified. ``` So for snowflake the the order of the values within the returned array is unspecified. for Databrick: [](https://docs.databricks.com/en/sql/language-manual/functions/array_except.html) it also not explain the null situation and the order of the values within the returned array for spark: [](https://spark.apache.org/docs/3.1.3/api/python/reference/api/pyspark.sql.functions.array_except.html) it also not explain the null situation and the order of the values within the returned array for prestodb: [](https://prestodb.io/docs/current/search.html?q=array_except#) it also not explain the null situation and the order of the values within the returned array for Doris: [](https://doris.apache.org/docs/1.2/sql-manual/sql-functions/array-functions/array_except/) The order of order of the values within the returned array is specified. the order is same as array1 But if any input array is null, it will return null in the end. -- This is an automated message from the Apache Git Service. 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