FunctionParams.java

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

import org.apache.doris.catalog.FunctionSignature;
import org.apache.doris.nereids.analyzer.Unbound;
import org.apache.doris.nereids.trees.expressions.Expression;
import org.apache.doris.nereids.util.MoreFieldsThread;

import com.google.common.collect.ImmutableList;

import java.util.List;
import java.util.Optional;
import java.util.function.Supplier;
import javax.annotation.Nullable;

/**
 * This class is used to reuse the origin function's resolved signature to keep signature computation idempotent.
 * The resolved overload, coercion, and precision remain frozen even when a rewrite replaces children with the
 * already-coerced types recorded by that signature. Functions with child-derived complex metadata can refresh only
 * that metadata through {@link ComputeSignature#refreshDerivedSignature(FunctionSignature, List)}.
 * You should provide a private/protected constructor to pass through FunctionParams to the super class(BoundFunction),
 * and override `withChildren(List<Expression> children)` to build FunctionParams and create a new function
 * with the FunctionParams
 */
public class FunctionParams {
    public final Optional<BoundFunction> originFunction;
    public final String functionName;
    public final List<Expression> arguments;
    public final boolean inferred;

    public FunctionParams(String functionName, List<Expression> arguments) {
        this(null, functionName, arguments, false);
    }

    public FunctionParams(
            @Nullable BoundFunction originFunction, String functionName,
            List<Expression> arguments, boolean inferred) {
        this.originFunction = MoreFieldsThread.isKeepFunctionSignature()
                ? Optional.ofNullable(originFunction) : Optional.empty();
        this.functionName = functionName;
        this.arguments = arguments;
        this.inferred = inferred;
    }

    /**
     * Build one immutable context tying the lazy resolved signature to the exact immediate-origin arguments.
     * Reuse is disabled when either tree is still unbound so normal analysis can establish a fresh binding.
     */
    @Nullable
    public SignatureReuseContext getSignatureReuseContext() {
        if (!originFunction.isPresent()
                || originFunction.get().containsType(Unbound.class)
                || arguments.stream().anyMatch(argument -> argument.containsType(Unbound.class))) {
            return null;
        }
        BoundFunction origin = originFunction.get();
        return new SignatureReuseContext(origin::getSignature, origin.getArguments());
    }

    /** A coherent snapshot used for one withChildren signature-reuse step. */
    public static final class SignatureReuseContext {
        private final Supplier<FunctionSignature> resolvedSignature;
        private final ImmutableList<Expression> immediateOriginArguments;

        private SignatureReuseContext(
                Supplier<FunctionSignature> resolvedSignature, List<Expression> immediateOriginArguments) {
            this.resolvedSignature = resolvedSignature;
            this.immediateOriginArguments = ImmutableList.copyOf(immediateOriginArguments);
        }

        public FunctionSignature getResolvedSignature() {
            return resolvedSignature.get();
        }

        public List<Expression> getImmediateOriginArguments() {
            return immediateOriginArguments;
        }
    }
}