AggregateFunction.java

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

import org.apache.doris.nereids.exceptions.UnboundException;
import org.apache.doris.nereids.trees.expressions.Expression;
import org.apache.doris.nereids.trees.expressions.functions.BoundFunction;
import org.apache.doris.nereids.trees.expressions.typecoercion.ExpectsInputTypes;
import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitor;
import org.apache.doris.nereids.types.DataType;
import org.apache.doris.nereids.types.PartialAggType;
import org.apache.doris.nereids.types.VarcharType;

import com.google.common.collect.ImmutableList;

import java.util.List;
import java.util.Objects;
import java.util.stream.Collectors;

/**
 * The function which consume arguments in lots of rows and product one value.
 */
public abstract class AggregateFunction extends BoundFunction implements ExpectsInputTypes {

    protected final boolean distinct;

    public AggregateFunction(String name, Expression... arguments) {
        this(name, false, arguments);
    }

    public AggregateFunction(String name, boolean distinct, Expression... arguments) {
        super(name, arguments);
        this.distinct = distinct;
    }

    public AggregateFunction(String name, List<Expression> children) {
        this(name, false, children);
    }

    public AggregateFunction(String name, boolean distinct, List<Expression> children) {
        super(name, children);
        this.distinct = distinct;
    }

    protected List<DataType> intermediateTypes() {
        return ImmutableList.of(VarcharType.SYSTEM_DEFAULT);
    }

    @Override
    public AggregateFunction withChildren(List<Expression> children) {
        return withDistinctAndChildren(distinct, children);
    }

    public abstract AggregateFunction withDistinctAndChildren(boolean distinct, List<Expression> children);

    /** getIntermediateTypes */
    public final PartialAggType getIntermediateTypes() {
        return new PartialAggType(getArguments(), intermediateTypes());
    }

    public boolean isDistinct() {
        return distinct;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }
        AggregateFunction that = (AggregateFunction) o;
        return Objects.equals(distinct, that.distinct)
                && Objects.equals(getName(), that.getName())
                && Objects.equals(children, that.children);
    }

    @Override
    public int computeHashCode() {
        return Objects.hash(distinct, getName(), children);
    }

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

    @Override
    public boolean hasVarArguments() {
        return false;
    }

    @Override
    public String computeToSql() throws UnboundException {
        StringBuilder sql = new StringBuilder(getName()).append("(");
        if (distinct) {
            sql.append("DISTINCT ");
        }
        int arity = arity();
        for (int i = 0; i < arity; i++) {
            sql.append(child(i).toSql());
            if (i + 1 < arity) {
                sql.append(", ");
            }
        }
        return sql.append(")").toString();
    }

    @Override
    public String toString() {
        String args = children()
                .stream()
                .map(Expression::toString)
                .collect(Collectors.joining(", "));
        return getName() + "(" + (distinct ? "DISTINCT " : "") + args + ")";
    }

    public boolean supportAggregatePhase(AggregatePhase aggregatePhase) {
        return true;
    }

    public List<Expression> getDistinctArguments() {
        return distinct ? getArguments() : ImmutableList.of();
    }

    public boolean mustUseMultiDistinctAgg() {
        return false;
    }
}