<models>
    <catalogsearch>
        <rewrite>
            <fulltext>Sanv_CatalogSearch_Model_Fulltext</fulltext>
        </rewrite>
    </catalogsearch_resource>
</models>

但是如果想复写catalogsearch model下resource目录下的东西，以这种方式就无法重写

错误的重写方式：

<catalogsearch>
        <rewrite>
            <resource_fulltext>Sanv_CatalogSearch_Model_Resource_Fulltext</resource_fulltext>
        </rewrite>
    </catalogsearch_resource>
</models>

正确的重写方式：

<models>
    <catalogsearch_resource>
        <rewrite>
            <fulltext>Sanv_CatalogSearch_Model_Resource_Fulltext</fulltext>
        </rewrite>
    </catalogsearch_resource>
</models>