From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from localhost (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id A591F26610 for ; Mon, 23 Jul 2018 12:39:45 -0400 (EDT) Received: from turing.freelists.org ([127.0.0.1]) by localhost (turing.freelists.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id HbqNm_IQNgak for ; Mon, 23 Jul 2018 12:39:45 -0400 (EDT) Received: from smtp54.i.mail.ru (smtp54.i.mail.ru [217.69.128.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTPS id 5DD4322C26 for ; Mon, 23 Jul 2018 12:39:45 -0400 (EDT) Subject: [tarantool-patches] Re: [PATCH v1 1/1] sql: prevent executing crossengine sql References: <6134a0afdcfba13ca289e2d42fdd529a2787070a.1532094680.git.kshcherbatov@tarantool.org> <50ac96b7-d395-f528-f66b-c10847e54670@tarantool.org> <812d64bf-a5a8-805d-d353-32f6733a41b9@tarantool.org> <26691970-9406-1cd2-e2ea-3e78b4d7b145@tarantool.org> From: Vladislav Shpilevoy Message-ID: Date: Mon, 23 Jul 2018 19:39:42 +0300 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format="flowed" Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: tarantool-patches-bounce@freelists.org Errors-to: tarantool-patches-bounce@freelists.org Reply-To: tarantool-patches@freelists.org List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-Id: tarantool-patches List-subscribe: List-owner: List-post: List-archive: To: "n.pettik" , tarantool-patches@freelists.org Cc: Kirill Shcherbatov On 23/07/2018 19:20, n.pettik wrote: > >>> struct iterator *it = index_create_iterator(*pCur->space->index, >>> ITER_ALL, nil_key, >>> 0 /* part_count */); >>> @@ -1134,12 +1135,26 @@ cursor_seek(BtCursor *pCur, int *pRes) >>> return SQL_TARANTOOL_ITERATOR_FAIL; >>> } >>> + struct space *space = pCur->space; >>> + struct txn *txn = NULL;> + >>> + assert(space->def->id != 0 || space_is_memtx(space)); >>> + if (space->def->id != 0 &&> + space->def->id != BOX_SQL_STAT4_ID && >>> + space->def->id != BOX_SQL_STAT1_ID) { >> >> 2. I strongly do not like these 3 checks. >> >> * space->id == 0 can be skipped, since begin_ro_stmt needs >> only space engine. >> >> * id != stat4/1 is a huge crutch that should be removed. The >> later will be dilapidated by any stat or tx manager change. >> I guess it is because of ANALYZE that scans spaces and then >> updates _stat1/4. But I can not understand, why it can not >> firstly read the samples from user spaces, commit ro, and >> secondly insert the samples into stats in another transaction. >> Besides, I believe, that user spaces and analyze ones should >> not be in a single transaction ever as former are actually >> system ones and should not be mixed with user spaces. >> Nikita, I appeal to you for onlooking. Is it possible to >> split ANALYZE in two transactions? How could Kirill do it? >> Besides there is another option, but IMHO it could seem even >> more flawed. > > Why do you think so? I am afraid of additional 'if's for such internal thing. > Actually, I can’t come up with better solution: > when we start executing OP_AnalysisLoad we always start transaction > (member that issue with gathering statistics on region to make it consistent? > See sql_analysis_load()). I think that on insertion into analyze spaces we correctly start a transaction, and it is not for region usage only. As I remember, there were problems with stat spaces consistency if we update stat not in a transaction. Region is just a convenient benefit. > Mb we always can avoid calling txn_begin_ro_stmt() on system spaces? It is okay, but for ephemeral spaces too, it is not? On the parsing stage we know is the space system one or not. Besides, I think that if a user calls explicit "SELECT * FROM _space", we should begin ro, but not when we open an internal cursor (ephemeral, or to insert into stats or something). It looks like a good question for the server team chat - should be start read-only statements on explicit SELECT from a system space? Box API now does it (inside box_index_iterator()). > > Quite similar to this issue might be CREATE TABLE AS SELECT > when it will be implemented. However, in this case we still can avoid > mixing user and system spaces within one transaction: > > INSERT TO _SPACE/_INDEX etc > SELECT FROM source INSERT TO ephemeral > START TRANSACTION > SELECT FROM ephemeral INSERT TO destination > COMMIT TRANSACTION Then I do not understand why can not we do the same for ANALYZE: SELECT samples from different engines with no ro stmts; START TX; INSERT tuples into stat1/4; COMMIT; > >> We could introduce a new opcode or add an option >> for OP_Seek like 'is_atomic' that will trigger ro stmt start. >> For spaces like analyze and ephemeral ones we could set this >> option in True thereby "allowing" cross-engine transactions >> for internal usage when we do not need read-view and other tx >> manager facilities. >> >> >>> + if (txn_begin_ro_stmt(space, &txn) != 0) >>> + return SQL_TARANTOOL_ERROR; >>> + } >>> struct iterator *it = index_create_iterator(pCur->index, pCur->iter_type, >>> key, part_count); >>> if (it == NULL) { >>> + if (txn != NULL) >>> + txn_rollback_stmt(); >>> pCur->eState = CURSOR_INVALID; >>> return SQL_TARANTOOL_ITERATOR_FAIL; >>> } >>> + if (txn != NULL) >>> + txn_commit_ro_stmt(txn); >>> pCur->iter = it; >>> pCur->eState = CURSOR_VALID; >>> >> >