NgramSearch.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.exceptions.AnalysisException;
import org.apache.doris.nereids.trees.expressions.Expression;
import org.apache.doris.nereids.trees.expressions.functions.ExplicitlyCastableSignature;
import org.apache.doris.nereids.trees.expressions.functions.PropagateNullable;
import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitor;
import org.apache.doris.nereids.types.DoubleType;
import org.apache.doris.nereids.types.IntegerType;
import org.apache.doris.nereids.types.StringType;

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

import java.util.List;

/**
 * ScalarFunction 'NgramSearch'.
 */
public class NgramSearch extends ScalarFunction
        implements ExplicitlyCastableSignature, PropagateNullable {

    public static final List<FunctionSignature> SIGNATURES = ImmutableList.of(
            FunctionSignature.ret(DoubleType.INSTANCE).args(StringType.INSTANCE, StringType.INSTANCE,
                    IntegerType.INSTANCE));

    /**
     * constructor with 3 argument.
     */
    public NgramSearch(Expression arg0, Expression arg1, Expression arg2) {
        super("ngram_search", arg0, arg1, arg2);
        if (!(arg1.isConstant())) {
            throw new AnalysisException(
                    "ngram_search(text,pattern,gram_num): pattern support const value only.");
        }
        if (!(arg2.isConstant())) {
            throw new AnalysisException(
                    "ngram_search(text,pattern,gram_num): gram_num support const value only.");
        }
    }

    /**
     * withChildren.
     */
    @Override
    public NgramSearch withChildren(List<Expression> children) {
        Preconditions.checkArgument(children.size() == 3);
        return new NgramSearch(children.get(0), children.get(1), children.get(2));
    }

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

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