HammingDistance.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.exceptions.AnalysisException;
import org.apache.doris.nereids.trees.expressions.Expression;
import org.apache.doris.nereids.trees.expressions.functions.AlwaysNotNullable;
import org.apache.doris.nereids.trees.expressions.functions.ExplicitlyCastableSignature;
import org.apache.doris.nereids.trees.expressions.shape.BinaryExpression;
import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitor;
import org.apache.doris.nereids.types.ArrayType;
import org.apache.doris.nereids.types.BigIntType;
import org.apache.doris.nereids.types.DataType;
import org.apache.doris.nereids.types.FloatType;

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

import java.util.List;

/**
 * hamming_distance function
 */
public class HammingDistance extends ScalarFunction implements ExplicitlyCastableSignature,
        BinaryExpression, AlwaysNotNullable {

    public static final List<FunctionSignature> SIGNATURES = ImmutableList.of(
            FunctionSignature.ret(FloatType.INSTANCE)
                    .args(ArrayType.of(BigIntType.INSTANCE), ArrayType.of(BigIntType.INSTANCE))
    );

    /**
     * Constructor with two vector arguments.
     */
    public HammingDistance(Expression arg0, Expression arg1) {
        super("hamming_distance", arg0, arg1);
    }

    /** constructor for withChildren and reuse signature */
    private HammingDistance(ScalarFunctionParams functionParams) {
        super(functionParams);
    }

    /**
     * withChildren.
     */
    @Override
    public HammingDistance withChildren(List<Expression> children) {
        Preconditions.checkArgument(children.size() == 2);
        return new HammingDistance(getFunctionParams(children));
    }

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

    @Override
    public void checkLegalityBeforeTypeCoercion() {
        validateByteArguments(getArguments());
    }

    static void validateByteArguments(List<Expression> arguments) {
        // Validate before implicit casts can truncate fractions or wrap integers wider than BIGINT.
        for (Expression argument : arguments) {
            DataType type = argument.getDataType();
            if (type.isNullType()) {
                continue;
            }
            if (type instanceof ArrayType) {
                DataType itemType = ((ArrayType) type).getItemType();
                if (itemType.isNullType() || (itemType.isIntegralType() && !itemType.isLargeIntType())) {
                    continue;
                }
            }
            throw new AnalysisException("Hamming distance requires integer arrays with elements in [0, 255]");
        }
    }

    @Override
    public List<FunctionSignature> getSignatures() {
        return SIGNATURES;
    }
}