CountByEnum.java

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

import org.apache.doris.catalog.FunctionSignature;
import org.apache.doris.nereids.trees.expressions.Expression;
import org.apache.doris.nereids.trees.expressions.functions.ExplicitlyCastableSignature;
import org.apache.doris.nereids.trees.expressions.literal.StringLiteral;
import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitor;
import org.apache.doris.nereids.types.StringType;
import org.apache.doris.nereids.util.ExpressionUtils;

import com.google.common.collect.ImmutableList;

import java.util.List;

/** count_by_enum agg function. */
public class CountByEnum extends NotNullableAggregateFunction implements ExplicitlyCastableSignature {

    public static final List<FunctionSignature> SIGNATURES = ImmutableList.of(
            FunctionSignature.ret(StringType.INSTANCE).varArgs(StringType.INSTANCE)
    );

    public CountByEnum(Expression arg0, Expression... varArgs) {
        super("count_by_enum", ExpressionUtils.mergeArguments(arg0, varArgs));
    }

    public CountByEnum(boolean distinct, Expression arg0, Expression... varArgs) {
        super("count_by_enum", distinct, ExpressionUtils.mergeArguments(arg0, varArgs));
    }

    private CountByEnum(boolean distinct, Expression... varArgs) {
        super("count_by_enum", distinct, varArgs);
    }

    @Override
    public AggregateFunction withDistinctAndChildren(boolean distinct, List<Expression> children) {
        return new CountByEnum(distinct, children.toArray(new Expression[0]));
    }

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

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

    @Override
    public Expression resultForEmptyInput() {
        return new StringLiteral("[]");
    }
}