UnboundAlias.java

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package org.apache.doris.nereids.analyzer;

import org.apache.doris.nereids.exceptions.UnboundException;
import org.apache.doris.nereids.trees.expressions.Expression;
import org.apache.doris.nereids.trees.expressions.NamedExpression;
import org.apache.doris.nereids.trees.expressions.functions.PropagateNullable;
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 com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;

import java.util.List;
import java.util.Optional;

/**
 * Expression for unbound alias.
 */
public class UnboundAlias extends NamedExpression implements UnaryExpression, Unbound, PropagateNullable {

    private final Optional<String> alias;
    private final boolean nameFromChild;

    public UnboundAlias(Expression child) {
        this(ImmutableList.of(child), Optional.empty());
    }

    public UnboundAlias(Expression child, String alias) {
        this(ImmutableList.of(child), Optional.of(alias));
    }

    public UnboundAlias(Expression child, String alias, boolean nameFromChild) {
        this(ImmutableList.of(child), Optional.of(alias), nameFromChild);
    }

    private UnboundAlias(List<Expression> children, Optional<String> alias) {
        this(children, alias, false);
    }

    private UnboundAlias(List<Expression> children, Optional<String> alias, boolean nameFromChild) {
        super(children);
        this.alias = alias;
        this.nameFromChild = nameFromChild;
    }

    @Override
    public DataType getDataType() throws UnboundException {
        return child().getDataType();
    }

    @Override
    public String computeToSql() {
        StringBuilder stringBuilder = new StringBuilder();
        stringBuilder.append("(" + child() + ")");
        alias.ifPresent(name -> stringBuilder.append(" AS " + name));
        return stringBuilder.toString();

    }

    @Override
    public String toString() {
        StringBuilder stringBuilder = new StringBuilder();
        stringBuilder.append("UnboundAlias(" + child() + ")");
        alias.ifPresent(name -> stringBuilder.append(" AS " + name));
        return stringBuilder.toString();
    }

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

    @Override
    public UnboundAlias withChildren(List<Expression> children) {
        Preconditions.checkArgument(children.size() == 1);
        return new UnboundAlias(children, alias);
    }

    public Optional<String> getAlias() {
        return alias;
    }

    public boolean isNameFromChild() {
        return nameFromChild;
    }
}