Max.java

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package org.apache.doris.nereids.trees.expressions.functions.agg;

import org.apache.doris.catalog.FunctionSignature;
import org.apache.doris.catalog.Type;
import org.apache.doris.nereids.exceptions.AnalysisException;
import org.apache.doris.nereids.trees.expressions.Expression;
import org.apache.doris.nereids.trees.expressions.functions.CustomSignature;
import org.apache.doris.nereids.trees.expressions.functions.Function;
import org.apache.doris.nereids.trees.expressions.functions.window.SupportWindowAnalytic;
import org.apache.doris.nereids.trees.expressions.shape.UnaryExpression;
import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitor;
import org.apache.doris.nereids.types.DataType;
import org.apache.doris.nereids.types.DecimalV2Type;
import org.apache.doris.nereids.types.DecimalV3Type;

import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;

import java.util.List;

/** max agg function. */
public class Max extends NullableAggregateFunction
        implements UnaryExpression, CustomSignature, SupportWindowAnalytic, RollUpTrait {
    public Max(Expression child) {
        this(false, false, child);
    }

    public Max(boolean distinct, Expression arg) {
        this(distinct, false, arg);
    }

    private Max(boolean distinct, boolean alwaysNullable, Expression arg) {
        super("max", false, alwaysNullable, arg);
    }

    @Override
    public void checkLegalityBeforeTypeCoercion() {
        if (getArgumentType(0).isOnlyMetricType()) {
            throw new AnalysisException(Type.OnlyMetricTypeErrorMsg);
        }
    }

    @Override
    public FunctionSignature customSignature() {
        DataType dataType = getArgument(0).getDataType();
        if (dataType instanceof DecimalV2Type) {
            dataType = DecimalV3Type.forType(dataType);
        }
        return FunctionSignature.ret(dataType).args(dataType);
    }

    @Override
    protected List<DataType> intermediateTypes() {
        return ImmutableList.of(getDataType());
    }

    @Override
    public Max withDistinctAndChildren(boolean distinct, List<Expression> children) {
        Preconditions.checkArgument(children.size() == 1);
        return new Max(distinct, alwaysNullable, children.get(0));
    }

    @Override
    public NullableAggregateFunction withAlwaysNullable(boolean alwaysNullable) {
        return new Max(distinct, alwaysNullable, children.get(0));
    }

    @Override
    public <R, C> R accept(ExpressionVisitor<R, C> visitor, C context) {
        return visitor.visitMax(this, context);
    }

    @Override
    public Function constructRollUp(Expression param, Expression... varParams) {
        return new Max(this.distinct, this.alwaysNullable, param);
    }

    @Override
    public boolean canRollUp() {
        return true;
    }
}