dawidwys commented on code in PR #23173: URL: https://github.com/apache/flink/pull/23173#discussion_r1496017400
########## 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: I see there is one more question to answear from Snowflake's docs: > ARRAY_EXCEPT compares arrays by using multi-set semantics (sometimes called “bag semantics”). If source_array includes multiple copies of a value, the function only removes the number of copies of that value that are specified in array_of_elements_to_exclude. > In other words, if source_array has N copies of a value and array_of_elements_to_exclude has M copies of the same value, the function excludes M copies of the value from the returned array. The number of copies of the value in the returned array is N - M or, if M is larger than N, 0. > For example, if source_array contains 5 elements with the value 'A' and array_of_elements_to_exclude contains 2 elements with the value 'A', the returned array contains 3 elements with the value 'A'. Do we want that behaviour or deduplicate behaviour? cc @MartijnVisser WDYT? 1. Should we deduplicate (set semantics) or remove only the number of elements from array2 (multi-set) ? 2. What should be the order in the resulting array? -- This is an automated message from the Apache Git Service. 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