PostgreSQL 模式删除背后的代码

/*                                    
 * Guts of schema deletion.                                    
 */                                    
void                                    
RemoveSchemaById(Oid schemaOid)                                    
{                                    
    Relation    relation;                            
    HeapTuple    tup;                            
                                    
    relation = heap_open(NamespaceRelationId, RowExclusiveLock);                                
                                    
    tup = SearchSysCache1(NAMESPACEOID,                                
                          ObjectIdGetDatum(schemaOid));            
    if (!HeapTupleIsValid(tup)) /* should not happen */                                
        elog(ERROR, "cache lookup failed for namespace %u", schemaOid);                            
                                    
    simple_heap_delete(relation, &tup->t_self);                                
                                    
    ReleaseSysCache(tup);                                
                                    
    heap_close(relation, RowExclusiveLock);                                
}