在浏览AGE代码时，我发现了这个age-1.3.0.sql文件，我相信所有的表都是在这里创建的，所有的函数都是在这里声明的。
例如行号94

CREATE FUNCTION ag_catalog.create_graph(graph_name name)
RETURNS void
LANGUAGE c
AS 'MODULE_PATHNAME';

我假设这是create_graph函数的声明。
我在age.control文件的第20行找到了MODULE_PATHNAME可能引用的内容

module_pathname = '$libdir/age'

和C函数的定义来创建一个图，我想是这个函数在/src/backend/commands/graph_commands. c行号60：-

/* function that is evoked for creating a graph */
Datum create_graph(PG_FUNCTION_ARGS)
{
    char *graph;
    Name graph_name;
    char *graph_name_str;
    Oid nsp_id;

    //if no argument is passed with the function, graph name cannot be null
    if (PG_ARGISNULL(0))
    {
        ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                        errmsg("graph name can not be NULL")));
    }

    //gets graph name as function argument
    graph_name = PG_GETARG_NAME(0);  

    graph_name_str = NameStr(*graph_name);

    //checking if the name of the graph falls under the pre-decided graph naming conventions(regex)
    if (!is_valid_graph_name(graph_name_str))
    {
        ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                        errmsg("graph name is invalid")));
    }

    //graph name must be unique, a graph with the same name should not exist
    if (graph_exists(graph_name_str))
    {
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_SCHEMA),
                 errmsg("graph \"%s\" already exists", graph_name_str)));
    }

    nsp_id = create_schema_for_graph(graph_name);

    //inserts the graph info into the relation which has all the other existing graphs info
    insert_graph(graph_name, nsp_id);  

    //Increment the Command counter before create the generic labels.
    CommandCounterIncrement();

    //Create the default label tables
    graph = graph_name->data;
    create_label(graph, AG_DEFAULT_LABEL_VERTEX, LABEL_TYPE_VERTEX, NIL);
    create_label(graph, AG_DEFAULT_LABEL_EDGE, LABEL_TYPE_EDGE, NIL);

    ereport(NOTICE,
            (errmsg("graph \"%s\" has been created", NameStr(*graph_name))));

    //according to postgres specification of c-language functions if function returns void this is the syntax
    PG_RETURN_VOID(); 
}

我想问的是，当一个SQL查询

SELECT * FROM ag_catalog.create_graph('graph_name');

执行时，执行上述文件中的C函数？两者之间的链接在哪里？在哪里可以找到？
我已经深入挖掘了大量的代码，但无济于事，我仍然不明白这一切是如何联系在一起的。