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73291de74e
In commit aa719b5010 (part of MDEV-32050)
a bug was introduced in the function purge_sys_t::choose_next_log(),
which reimplements some logic that previously was part of
trx_purge_read_undo_rec(). We must invoke trx_undo_get_first_rec()
with the page number and offset of the undo log header, but we were
incorrectly invoking it on the current undo page number, which caused
us to parse undo records starting at an incorrect offset.
purge_sys_t::choose_next_log(): Pass the correct parameter to
trx_undo_page_get_first_rec().
trx_undo_page_get_next_rec(), trx_undo_page_get_first_rec(),
trx_undo_page_get_last_rec(): Add debug assertions and make the
code more robust by returning nullptr on corruption. Should we
detect any corrupted undo logs during the purge of committed
transaction history, the sanest thing to do is to pretend that
the end of an undo log was reached. If any garbage is left in
the tables, it will be ignored by anything else than
CHECK TABLE ... EXTENDED, and it can be removed by OPTIMIZE TABLE.
Thanks to Matthias Leich for providing an "rr replay" trace where
this bug could be found.
Reviewed by: Vladislav Lesin
130 lines
4.7 KiB
C++
130 lines
4.7 KiB
C++
/*****************************************************************************
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Copyright (c) 1996, 2013, Oracle and/or its affiliates. All Rights Reserved.
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Copyright (c) 2017, 2022, MariaDB Corporation.
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This program is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free Software
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Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along with
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this program; if not, write to the Free Software Foundation, Inc.,
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51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA
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*****************************************************************************/
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/**************************************************//**
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@file include/trx0undo.ic
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Transaction undo log
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Created 3/26/1996 Heikki Tuuri
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*******************************************************/
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#include "data0type.h"
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#include "page0page.h"
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/***********************************************************************//**
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Builds a roll pointer.
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@return roll pointer */
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UNIV_INLINE
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roll_ptr_t
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trx_undo_build_roll_ptr(
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/*====================*/
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bool is_insert, /*!< in: TRUE if insert undo log */
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ulint rseg_id, /*!< in: rollback segment id */
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uint32_t page_no, /*!< in: page number */
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uint16_t offset) /*!< in: offset of the undo entry within page */
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{
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compile_time_assert(DATA_ROLL_PTR_LEN == 7);
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ut_ad(rseg_id < TRX_SYS_N_RSEGS);
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return roll_ptr_t{is_insert} << ROLL_PTR_INSERT_FLAG_POS |
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roll_ptr_t{rseg_id} << ROLL_PTR_RSEG_ID_POS |
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roll_ptr_t{page_no} << ROLL_PTR_PAGE_POS | offset;
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}
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/***********************************************************************//**
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Decodes a roll pointer. */
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UNIV_INLINE
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void
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trx_undo_decode_roll_ptr(
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/*=====================*/
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roll_ptr_t roll_ptr, /*!< in: roll pointer */
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bool* is_insert, /*!< out: TRUE if insert undo log */
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ulint* rseg_id, /*!< out: rollback segment id */
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uint32_t* page_no, /*!< out: page number */
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uint16_t* offset) /*!< out: offset of the undo
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entry within page */
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{
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compile_time_assert(DATA_ROLL_PTR_LEN == 7);
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ut_ad(roll_ptr < (1ULL << 56));
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*offset= static_cast<uint16_t>(roll_ptr);
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*page_no= static_cast<uint32_t>(roll_ptr >> 16);
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*rseg_id= static_cast<ulint>(roll_ptr >> 48 & 0x7F);
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*is_insert= static_cast<bool>(roll_ptr >> 55);
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}
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/***********************************************************************//**
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Determine if DB_ROLL_PTR is of the insert type.
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@return true if insert */
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UNIV_INLINE
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bool
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trx_undo_roll_ptr_is_insert(
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/*========================*/
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roll_ptr_t roll_ptr) /*!< in: roll pointer */
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{
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compile_time_assert(DATA_ROLL_PTR_LEN == 7);
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ut_ad(roll_ptr < (1ULL << (ROLL_PTR_INSERT_FLAG_POS + 1)));
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return static_cast<bool>(roll_ptr >> ROLL_PTR_INSERT_FLAG_POS);
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}
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/***********************************************************************//**
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Returns true if the record is of the insert type.
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@return true if the record was freshly inserted (not updated). */
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UNIV_INLINE
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bool
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trx_undo_trx_id_is_insert(
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/*======================*/
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const byte* trx_id) /*!< in: DB_TRX_ID, followed by DB_ROLL_PTR */
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{
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compile_time_assert(DATA_TRX_ID + 1 == DATA_ROLL_PTR);
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return bool(trx_id[DATA_TRX_ID_LEN] >> 7);
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}
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/** Determine the end offset of undo log records of an undo log page.
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@param[in] undo_page undo log page
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@param[in] page_no undo log header page number
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@param[in] offset undo log header offset
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@return end offset */
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inline
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uint16_t trx_undo_page_get_end(const buf_block_t *undo_page, uint32_t page_no,
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uint16_t offset)
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{
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if (page_no == undo_page->page.id().page_no())
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if (uint16_t end = mach_read_from_2(TRX_UNDO_NEXT_LOG + offset +
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undo_page->page.frame))
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return end;
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return mach_read_from_2(TRX_UNDO_PAGE_HDR + TRX_UNDO_PAGE_FREE +
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undo_page->page.frame);
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}
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/** Get the next record in an undo log.
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@param[in] undo_page undo log page
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@param[in] rec undo record offset in the page
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@param[in] page_no undo log header page number
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@param[in] offset undo log header offset on page
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@return undo log record, the page latched, NULL if none */
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inline trx_undo_rec_t*
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trx_undo_page_get_next_rec(const buf_block_t *undo_page, uint16_t rec,
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uint32_t page_no, uint16_t offset)
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{
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uint16_t end= trx_undo_page_get_end(undo_page, page_no, offset);
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uint16_t next= mach_read_from_2(undo_page->page.frame + rec);
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ut_ad(next <= end);
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return next >= end ? nullptr : undo_page->page.frame + next;
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}
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