ExplodeMapOuter.java

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

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.AlwaysNullable;
import org.apache.doris.nereids.trees.expressions.literal.StructLiteral;
import org.apache.doris.nereids.trees.expressions.shape.UnaryExpression;
import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitor;
import org.apache.doris.nereids.types.MapType;

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

import java.util.List;

/**
 * explode({"amory":1, "doris": 2}) generate two column and two lines with:
 *      key column: amory, doris
 *      value column: 1, 2
 */
public class ExplodeMapOuter extends TableGeneratingFunction implements UnaryExpression, AlwaysNullable {

    /**
     * constructor with 1 argument.
     */
    public ExplodeMapOuter(Expression arg) {
        super("explode_map_outer", arg);
    }

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

    @Override
    public void checkLegalityBeforeTypeCoercion() {
        if (!(child().getDataType() instanceof MapType)) {
            throw new AnalysisException("only support map type for explode_map function but got "
                    + child().getDataType());
        }
    }

    @Override
    public List<FunctionSignature> getSignatures() {
        return ImmutableList.of(
                FunctionSignature.ret(StructLiteral.constructStructType(
                                Lists.newArrayList(((MapType) child().getDataType()).getKeyType(),
                                        ((MapType) child().getDataType()).getValueType())))
                        .args(child().getDataType())
        );
    }

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