ArrayAvg.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.catalog.ScalarType;
import org.apache.doris.nereids.exceptions.AnalysisException;
import org.apache.doris.nereids.trees.expressions.Expression;
import org.apache.doris.nereids.trees.expressions.NeedSessionVarGuard;
import org.apache.doris.nereids.trees.expressions.functions.AlwaysNullable;
import org.apache.doris.nereids.trees.expressions.functions.ComputePrecisionForArrayItemAgg;
import org.apache.doris.nereids.trees.expressions.functions.ExplicitlyCastableSignature;
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.BigIntType;
import org.apache.doris.nereids.types.DataType;
import org.apache.doris.nereids.types.DecimalV3Type;
import org.apache.doris.nereids.types.DoubleType;
import org.apache.doris.nereids.types.FloatType;
import org.apache.doris.nereids.types.IntegerType;
import org.apache.doris.nereids.types.LargeIntType;
import org.apache.doris.nereids.types.SmallIntType;
import org.apache.doris.nereids.types.TinyIntType;
import org.apache.doris.qe.ConnectContext;

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

import java.util.List;

/**
 * ScalarFunction 'array_avg'. This class is generated by GenerateFunction.
 */
public class ArrayAvg extends ScalarFunction implements ExplicitlyCastableSignature,
        ComputePrecisionForArrayItemAgg, UnaryExpression, AlwaysNullable, NeedSessionVarGuard {

    public static final List<FunctionSignature> SIGNATURES = ImmutableList.of(
            FunctionSignature.ret(DoubleType.INSTANCE).args(ArrayType.of(DoubleType.INSTANCE)),
            FunctionSignature.ret(DoubleType.INSTANCE).args(ArrayType.of(TinyIntType.INSTANCE)),
            FunctionSignature.ret(DoubleType.INSTANCE).args(ArrayType.of(SmallIntType.INSTANCE)),
            FunctionSignature.ret(DoubleType.INSTANCE).args(ArrayType.of(IntegerType.INSTANCE)),
            FunctionSignature.ret(DoubleType.INSTANCE).args(ArrayType.of(BigIntType.INSTANCE)),
            FunctionSignature.ret(DoubleType.INSTANCE).args(ArrayType.of(LargeIntType.INSTANCE)),
            FunctionSignature.ret(DecimalV3Type.WILDCARD).args(ArrayType.of(DecimalV3Type.WILDCARD)),
            FunctionSignature.ret(DoubleType.INSTANCE).args(ArrayType.of(FloatType.INSTANCE))
    );

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

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

    /**
     * array_avg needs to calculate the average of the elements in the array.
     * so the element type must be numeric, boolean or string.
     */
    @Override
    public void checkLegalityBeforeTypeCoercion() {
        if (child(0).getDataType().isArrayType()
                && !((ArrayType) child(0).getDataType()).getItemType().canBeCalculatedInArray()) {
            throw new AnalysisException("array_avg does not support type "
                    + child(0).getDataType().toString() + ", expression is " + toSql());
        }
    }

    @Override
    public FunctionSignature computePrecision(FunctionSignature signature) {
        if (!(getArgumentType(0) instanceof ArrayType)) {
            return signature;
        }
        DataType argumentType = ((ArrayType) getArgumentType(0)).getItemType();
        if (!(argumentType instanceof DecimalV3Type)) {
            return signature;
        }
        boolean enableDecimal256 = false;
        ConnectContext connectContext = ConnectContext.get();
        if (connectContext != null) {
            enableDecimal256 = connectContext.getSessionVariable().isEnableDecimal256();
        }
        DecimalV3Type decimalV3Type = DecimalV3Type.forType(argumentType);
        // DecimalV3 scale lower than DEFAULT_MIN_AVG_DECIMAL128_SCALE should do cast
        int scale = decimalV3Type.getScale();
        if (decimalV3Type.getScale() < ScalarType.DEFAULT_MIN_AVG_DECIMAL128_SCALE) {
            scale = ScalarType.DEFAULT_MIN_AVG_DECIMAL128_SCALE;
        }
        return signature.withReturnType(DecimalV3Type.createDecimalV3Type(
                enableDecimal256 ? DecimalV3Type.MAX_DECIMAL256_PRECISION
                        : DecimalV3Type.MAX_DECIMAL128_PRECISION,
                scale)
        );
    }

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

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

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