MapFromEntries.java

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// to you under the Apache License, Version 2.0 (the
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//   http://www.apache.org/licenses/LICENSE-2.0
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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.PreferPushDownProject;
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.shape.UnaryExpression;
import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitor;
import org.apache.doris.nereids.types.ArrayType;
import org.apache.doris.nereids.types.DataType;
import org.apache.doris.nereids.types.MapType;
import org.apache.doris.nereids.types.StructField;
import org.apache.doris.nereids.types.StructType;

import com.google.common.base.Preconditions;

import java.util.List;

/** Construct a Map from an Array of two-field Struct entries. */
public class MapFromEntries extends ScalarFunction
        implements UnaryExpression, CustomSignature, PropagateNullable, PreferPushDownProject {

    public MapFromEntries(Expression entries) {
        super("map_from_entries", entries);
    }

    private MapFromEntries(ScalarFunctionParams functionParams) {
        super(functionParams);
    }

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

    @Override
    public FunctionSignature customSignature() {
        DataType inputType = getArgumentType(0);
        if (inputType.isNullType()) {
            return FunctionSignature.ret(MapType.SYSTEM_DEFAULT).args(inputType);
        }
        if (!(inputType instanceof ArrayType)
                || !(((ArrayType) inputType).getItemType() instanceof StructType)) {
            throw invalidInputType();
        }
        List<StructField> fields = ((StructType) ((ArrayType) inputType).getItemType()).getFields();
        if (fields.size() != 2) {
            throw invalidInputType();
        }
        MapType resultType = MapType.of(fields.get(0).getDataType(), fields.get(1).getDataType());
        resultType.validateDataType();
        return FunctionSignature.ret(resultType).args(inputType);
    }

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

    private AnalysisException invalidInputType() {
        return new AnalysisException(
                "map_from_entries requires an array of structs with exactly two fields");
    }
}