ArrayFlatten.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.CustomSignature;
import org.apache.doris.nereids.trees.expressions.functions.PropagateNullable;
import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitor;
import org.apache.doris.nereids.types.ArrayType;
import org.apache.doris.nereids.types.DataType;

import com.google.common.base.Preconditions;

import java.util.List;

/**
 * ScalarFunction 'array_flatten'
 */
public class ArrayFlatten extends ScalarFunction
        implements CustomSignature, PropagateNullable {

    /**
     * constructor with 1 arguments.
     */
    public ArrayFlatten(Expression arg) {
        super("array_flatten", arg);
    }

    @Override
    public FunctionSignature customSignature() {
        DataType dataType = getArgument(0).getDataType();
        while (dataType instanceof ArrayType) {
            dataType = ((ArrayType) dataType).getItemType();
        }
        return FunctionSignature.ret(ArrayType.of(dataType)).args(getArgument(0).getDataType());
    }

    /**
     * withChildren.
     */
    @Override
    public ArrayFlatten withChildren(List<Expression> children) {
        Preconditions.checkArgument(children.size() == 1);
        return new ArrayFlatten(children.get(0));
    }

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