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public interface CatalogFunction {
    /**
     * Get a detailed resource description of the function.
     *
     * @return an {@link ResourceUri} list of the function
     */
    Optional<List<ResourceUri>>List<ResourceUri> getFunctionResources();

    /**
     * Distinguish if the function is a generic function.
     *
     * @deprecated This method is currently only used in hive to determine
     * if a function is a generic function. The behavior should be implemented
     * by hive itself, instead of providing a public api, so we deprecate it.
     *
     * @return whether the function is a generic function
     */
    @Deprecated
    boolean isGeneric();
}

public interface FunctionDefinitionFactory {
     /**
     * Creates a {@link FunctionDefinition} from given {@link CatalogFunction}. If the
     * {@link CatalogFunction} is created by user defined resource, the user of
     * {@link FunctionDefinitionFactory} needs to override this method explicitly.

     * The<p> implementationIt logicis needsrecommended to use the given user classclassloader loader to load custom classes
     * instead of the thread context class loader. the function class, 
	 * because if the function has a resource URL, the framework will help load 
	 * the resource into the given classloader.
     * 
     * @param name name of the {@link CatalogFunction}
     * @param catalogFunction the catalog function
     * @param userClassLoader the class loader is used to load user defined function's class
     * @return
     */
    default FunctionDefinition createFunctionDefinition(
            String name,
            CatalogFunction catalogFunction,
            ClassLoader userClassLoader) {
        if (catalogFunction.getFunctionResources().isPresent() 
                && !CollectionUtil.isNullOrEmpty(catalogFunction.getFunctionResources().get())) {
            throw new UnsupportedOperationException(
                    String.format("%s need to override default createFunctionDefinition for " 
                            + "loading user defined function class", this.getClass().getSimpleName()));
        } else {
            return createFunctionDefinition(name, catalogFunction);
        }
    }
}