ExpressionVisitors.java

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package org.apache.doris.nereids.trees.expressions.visitor;

import org.apache.doris.nereids.trees.expressions.Expression;
import org.apache.doris.nereids.trees.expressions.WindowExpression;
import org.apache.doris.nereids.trees.expressions.functions.agg.AggregateFunction;

import java.util.Map;

/**
 * This is the factory for all ExpressionVisitor instance.
 * All children instance of DefaultExpressionVisitor or ExpressionVisitor for common usage
 * should be here and expose self by class static final field.
 */
public class ExpressionVisitors {

    public static final ContainsAggregateChecker CONTAINS_AGGREGATE_CHECKER = new ContainsAggregateChecker();
    public static final ExpressionMapReplacer EXPRESSION_MAP_REPLACER = new ExpressionMapReplacer();

    private static class ContainsAggregateChecker extends DefaultExpressionVisitor<Boolean, Void> {
        @Override
        public Boolean visit(Expression expr, Void context) {
            boolean needAggregate = false;
            for (Expression child : expr.children()) {
                needAggregate = needAggregate || child.accept(this, context);
            }
            return needAggregate;
        }

        @Override
        public Boolean visitWindow(WindowExpression windowExpression, Void context) {
            boolean needAggregate = false;
            for (Expression child : windowExpression.getExpressionsInWindowSpec()) {
                needAggregate = needAggregate || child.accept(this, context);
            }
            return needAggregate;
        }

        @Override
        public Boolean visitAggregateFunction(AggregateFunction aggregateFunction, Void context) {
            return true;
        }
    }

    /**
     * replace sub expr by Map
     */
    public static class ExpressionMapReplacer
            extends DefaultExpressionRewriter<Map<Expression, Expression>> {

        private ExpressionMapReplacer() {
        }

        @Override
        public Expression visit(Expression expr, Map<Expression, Expression> replaceMap) {
            if (replaceMap.containsKey(expr)) {
                return replaceMap.get(expr);
            }
            return super.visit(expr, replaceMap);
        }
    }
}