TryParseToVariant.java

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

import org.apache.doris.catalog.FunctionSignature;
import org.apache.doris.nereids.trees.expressions.Expression;
import org.apache.doris.nereids.trees.expressions.functions.AlwaysNullable;
import org.apache.doris.nereids.trees.expressions.functions.ExplicitlyCastableSignature;
import org.apache.doris.nereids.trees.expressions.shape.UnaryExpression;
import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitor;
import org.apache.doris.nereids.types.VarcharType;
import org.apache.doris.nereids.types.VariantType;

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

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

/** Parse JSON text into a Variant value and return SQL NULL for input errors. */
public class TryParseToVariant extends ScalarFunction
        implements UnaryExpression, ExplicitlyCastableSignature, AlwaysNullable {

    public static final List<FunctionSignature> SIGNATURES = ImmutableList.of(
            FunctionSignature.ret(VariantType.INSTANCE).args(VarcharType.SYSTEM_DEFAULT)
    );

    private final VariantType returnType;

    public TryParseToVariant(Expression argument) {
        this(argument, VariantType.INSTANCE);
    }

    public TryParseToVariant(Expression argument, VariantType returnType) {
        super("try_parse_to_variant", argument);
        this.returnType = returnType;
    }

    private TryParseToVariant(ScalarFunctionParams functionParams, VariantType returnType) {
        super(functionParams);
        this.returnType = returnType;
    }

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

    @Override
    public List<FunctionSignature> getSignatures() {
        return ImmutableList.of(FunctionSignature.ret(returnType).args(VarcharType.SYSTEM_DEFAULT));
    }

    @Override
    protected boolean extraEquals(Expression that) {
        return super.extraEquals(that) && returnType.equals(((TryParseToVariant) that).returnType);
    }

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

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