Cast.java

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//   http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.doris.nereids.trees.expressions;

import org.apache.doris.nereids.exceptions.UnboundException;
import org.apache.doris.nereids.trees.expressions.functions.Monotonic;
import org.apache.doris.nereids.trees.expressions.literal.Literal;
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.coercion.DateLikeType;

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

import java.util.List;
import java.util.Objects;

/**
 * cast function.
 */
public class Cast extends Expression implements UnaryExpression, Monotonic {

    // CAST can be from SQL Query or Type Coercion.
    private final boolean isExplicitType;

    private final DataType targetType;

    public Cast(Expression child, DataType targetType, boolean isExplicitType) {
        super(ImmutableList.of(child));
        this.targetType = Objects.requireNonNull(targetType, "targetType can not be null");
        this.isExplicitType = isExplicitType;
    }

    public Cast(Expression child, DataType targetType) {
        super(ImmutableList.of(child));
        this.targetType = Objects.requireNonNull(targetType, "targetType can not be null");
        this.isExplicitType = false;
    }

    private Cast(List<Expression> child, DataType targetType, boolean isExplicitType) {
        super(child);
        this.targetType = Objects.requireNonNull(targetType, "targetType can not be null");
        this.isExplicitType = isExplicitType;
    }

    public boolean isExplicitType() {
        return isExplicitType;
    }

    @Override
    public DataType getDataType() {
        return targetType;
    }

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

    @Override
    public boolean nullable() {
        DataType childDataType = child().getDataType();
        if (childDataType.isStringLikeType() && !targetType.isStringLikeType()) {
            return true;
        } else if (!childDataType.isDateLikeType() && targetType.isDateLikeType()) {
            return true;
        } else if (!childDataType.isTimeLikeType() && targetType.isTimeLikeType()) {
            return true;
        } else if (childDataType.isJsonType() || targetType.isJsonType()) {
            return true;
        } else if (childDataType.isVariantType() || targetType.isVariantType()) {
            return true;
        } else {
            return child().nullable();
        }
    }

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

    @Override
    public String computeToSql() throws UnboundException {
        return "cast(" + child().toSql() + " as " + targetType.toSql() + ")";
    }

    @Override
    public String toString() {
        return "cast(" + child() + " as " + targetType + ")";
    }

    @Override
    public boolean equals(Object o) {
        if (!super.equals(o)) {
            return false;
        }
        Cast cast = (Cast) o;
        return Objects.equals(targetType, cast.targetType);
    }

    @Override
    public int computeHashCode() {
        return Objects.hash(super.computeHashCode(), targetType);
    }

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

    @Override
    public int getMonotonicFunctionChildIndex() {
        return 0;
    }

    @Override
    public Expression withConstantArgs(Expression literal) {
        return new Cast(literal, targetType, isExplicitType);
    }

    @Override
    public boolean isMonotonic(Literal lower, Literal upper) {
        // Both upward and downward casting of date types satisfy monotonicity.
        if (child().getDataType() instanceof DateLikeType && targetType instanceof DateLikeType) {
            return true;
        }
        return false;
    }
}