morrySnow commented on code in PR #10947: URL: https://github.com/apache/doris/pull/10947#discussion_r923272111
########## fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/CaseWhen.java: ########## @@ -0,0 +1,122 @@ +// 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.doris.nereids.trees.expressions; + +import org.apache.doris.nereids.exceptions.UnboundException; +import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitor; +import org.apache.doris.nereids.types.DataType; + +import com.google.common.base.Preconditions; +import com.google.common.collect.ImmutableList; + +import java.util.ArrayList; +import java.util.List; +import java.util.Optional; +import java.util.stream.Collectors; + +/** + * The internal representation of + * CASE [expr] WHEN expr THEN expr [WHEN expr THEN expr ...] [ELSE expr] END + * Each When/Then is stored as two consecutive children (whenExpr, thenExpr). + * If a case expr is given, convert it to equalTo(caseExpr, whenExpr) and set it to whenExpr. + * If an else expr is given then it is the last child. + */ +public class CaseWhen extends Expression { + public CaseWhen(List<WhenClause> whenClauses) { + super(ExpressionType.CASE, whenClauses.toArray(new Expression[0])); + } + + public CaseWhen(List<WhenClause> whenClauses, Expression defaultValue) { + super(ExpressionType.CASE, + ImmutableList.builder().addAll(whenClauses).add(defaultValue).build().toArray(new Expression[0])); + } + + public List<WhenClause> getWhenClauses() { + List<WhenClause> whenClauses = children().stream() + .filter(e -> e instanceof WhenClause) + .map(e -> (WhenClause) e) + .collect(Collectors.toList()); + return whenClauses; + } + + public Optional<Expression> getDefaultValue() { + int lastIndex = children.size() - 1; Review Comment: maybe use a attribute to record default result offset is better ########## fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/CaseWhen.java: ########## @@ -0,0 +1,122 @@ +// 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.doris.nereids.trees.expressions; + +import org.apache.doris.nereids.exceptions.UnboundException; +import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitor; +import org.apache.doris.nereids.types.DataType; + +import com.google.common.base.Preconditions; +import com.google.common.collect.ImmutableList; + +import java.util.ArrayList; +import java.util.List; +import java.util.Optional; +import java.util.stream.Collectors; + +/** + * The internal representation of + * CASE [expr] WHEN expr THEN expr [WHEN expr THEN expr ...] [ELSE expr] END + * Each When/Then is stored as two consecutive children (whenExpr, thenExpr). + * If a case expr is given, convert it to equalTo(caseExpr, whenExpr) and set it to whenExpr. + * If an else expr is given then it is the last child. + */ +public class CaseWhen extends Expression { + public CaseWhen(List<WhenClause> whenClauses) { + super(ExpressionType.CASE, whenClauses.toArray(new Expression[0])); + } + + public CaseWhen(List<WhenClause> whenClauses, Expression defaultValue) { + super(ExpressionType.CASE, + ImmutableList.builder().addAll(whenClauses).add(defaultValue).build().toArray(new Expression[0])); + } + + public List<WhenClause> getWhenClauses() { + List<WhenClause> whenClauses = children().stream() + .filter(e -> e instanceof WhenClause) + .map(e -> (WhenClause) e) + .collect(Collectors.toList()); + return whenClauses; + } + + public Optional<Expression> getDefaultValue() { + int lastIndex = children.size() - 1; + if (child(lastIndex) instanceof WhenClause) { + return Optional.empty(); + } + return Optional.of(child(lastIndex)); + } + + public <R, C> R accept(ExpressionVisitor<R, C> visitor, C context) { + return visitor.visitCaseWhen(this, context); + } + + @Override + public DataType getDataType() { + return child(0).getDataType(); + } + + @Override + public boolean nullable() { + for (Expression child : children()) { + if (child.nullable()) { + return true; + } + } + return false; + } + + @Override + public String toString() { + return toSql(); + } + + @Override + public String toSql() throws UnboundException { + StringBuilder output = new StringBuilder("case"); Review Comment: ```suggestion StringBuilder output = new StringBuilder("CASE "); ``` ########## fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/WhenClause.java: ########## @@ -0,0 +1,91 @@ +// 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.doris.nereids.trees.expressions; + +import org.apache.doris.nereids.exceptions.UnboundException; +import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitor; +import org.apache.doris.nereids.types.DataType; + +import com.google.common.base.Preconditions; + +import java.util.List; +import java.util.Objects; + +/** + * captures info of a single WHEN expr THEN expr clause. + */ +public class WhenClause extends Expression implements BinaryExpression { + public WhenClause(Expression operand, Expression result) { + super(ExpressionType.WHEN_CLAUSE, operand, result); + } + + @Override + public String toSql() { + return "when " + left().toSql() + " then " + right().toSql(); Review Comment: nit: ```suggestion return "WHEN " + left().toSql() + " THEN " + right().toSql(); ``` ########## fe/fe-core/src/main/java/org/apache/doris/nereids/glue/translator/ExpressionTranslator.java: ########## @@ -213,6 +218,23 @@ public Expr visitStringRegexPredicate(StringRegexPredicate stringRegexPredicate, stringRegexPredicate.right().accept(this, context)); } + @Override + public Expr visitCaseWhen(CaseWhen caseWhen, PlanTranslatorContext context) { + List<CaseWhenClause> caseWhenClauses = new ArrayList<>(); + for (WhenClause whenClause : caseWhen.getWhenClauses()) { + caseWhenClauses.add(new CaseWhenClause( + whenClause.left().accept(this, context), + whenClause.right().accept(this, context) + )); + } + Expr elseExpr = null; + Optional<Expression> defaultValue = caseWhen.getDefaultValue(); Review Comment: nit: Optional is unnecessary -- This is an automated message from the Apache Git Service. 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