/***************************************************************************** Copyright (c) 1996, 2017, Oracle and/or its affiliates. All Rights Reserved. Copyright (c) 2017, 2021, MariaDB Corporation. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; version 2 of the License. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA *****************************************************************************/ /**************************************************//** @file trx/trx0purge.cc Purge old versions Created 3/26/1996 Heikki Tuuri *******************************************************/ #include "trx0purge.h" #include "fsp0fsp.h" #include "fut0fut.h" #include "mach0data.h" #include "mtr0log.h" #include "os0thread.h" #include "que0que.h" #include "row0purge.h" #include "row0upd.h" #include "srv0mon.h" #include "srv0srv.h" #include "srv0start.h" #include "sync0sync.h" #include "trx0rec.h" #include "trx0roll.h" #include "trx0rseg.h" #include "trx0trx.h" #include #include /** Maximum allowable purge history length. <=0 means 'infinite'. */ ulong srv_max_purge_lag = 0; /** Max DML user threads delay in micro-seconds. */ ulong srv_max_purge_lag_delay = 0; /** The global data structure coordinating a purge */ purge_sys_t purge_sys; /** A dummy undo record used as a return value when we have a whole undo log which needs no purge */ trx_undo_rec_t trx_purge_dummy_rec; #ifdef UNIV_DEBUG my_bool srv_purge_view_update_only_debug; #endif /* UNIV_DEBUG */ /** Sentinel value */ static const TrxUndoRsegs NullElement; /** Default constructor */ TrxUndoRsegsIterator::TrxUndoRsegsIterator() : m_rsegs(NullElement), m_iter(m_rsegs.begin()) { } /** Sets the next rseg to purge in purge_sys. Executed in the purge coordinator thread. @return whether anything is to be purged */ inline bool TrxUndoRsegsIterator::set_next() { mutex_enter(&purge_sys.pq_mutex); /* Only purge consumes events from the priority queue, user threads only produce the events. */ /* Check if there are more rsegs to process in the current element. */ if (m_iter != m_rsegs.end()) { /* We are still processing rollback segment from the same transaction and so expected transaction number shouldn't increase. Undo the increment of expected commit done by caller assuming rollback segments from given transaction are done. */ purge_sys.tail.trx_no = (*m_iter)->last_trx_no(); } else if (!purge_sys.purge_queue.empty()) { m_rsegs = purge_sys.purge_queue.top(); purge_sys.purge_queue.pop(); ut_ad(purge_sys.purge_queue.empty() || purge_sys.purge_queue.top() != m_rsegs); m_iter = m_rsegs.begin(); } else { /* Queue is empty, reset iterator. */ purge_sys.rseg = NULL; mutex_exit(&purge_sys.pq_mutex); m_rsegs = NullElement; m_iter = m_rsegs.begin(); return false; } purge_sys.rseg = *m_iter++; mutex_exit(&purge_sys.pq_mutex); mutex_enter(&purge_sys.rseg->mutex); ut_a(purge_sys.rseg->last_page_no != FIL_NULL); ut_ad(purge_sys.rseg->last_trx_no() == m_rsegs.trx_no); /* We assume in purge of externally stored fields that space id is in the range of UNDO tablespace space ids */ ut_ad(purge_sys.rseg->space->id == TRX_SYS_SPACE || srv_is_undo_tablespace(purge_sys.rseg->space->id)); ut_a(purge_sys.tail.trx_no <= purge_sys.rseg->last_trx_no()); purge_sys.tail.trx_no = purge_sys.rseg->last_trx_no(); purge_sys.hdr_offset = purge_sys.rseg->last_offset(); purge_sys.hdr_page_no = purge_sys.rseg->last_page_no; mutex_exit(&purge_sys.rseg->mutex); return(true); } /** Build a purge 'query' graph. The actual purge is performed by executing this query graph. @return own: the query graph */ static que_t* purge_graph_build() { ut_a(srv_n_purge_threads > 0); trx_t* trx = trx_create(); ut_ad(!trx->id); trx->start_time = time(NULL); trx->start_time_micro = microsecond_interval_timer(); trx->state = TRX_STATE_ACTIVE; trx->op_info = "purge trx"; mem_heap_t* heap = mem_heap_create(512); que_fork_t* fork = que_fork_create( NULL, NULL, QUE_FORK_PURGE, heap); fork->trx = trx; for (auto i = innodb_purge_threads_MAX; i; i--) { que_thr_t* thr = que_thr_create(fork, heap, NULL); thr->child = new(mem_heap_alloc(heap, sizeof(purge_node_t))) purge_node_t(thr); } return(fork); } /** Initialise the purge system. */ void purge_sys_t::create() { ut_ad(this == &purge_sys); ut_ad(!heap); ut_ad(!enabled()); m_paused= 0; query= purge_graph_build(); next_stored= false; rseg= NULL; page_no= 0; offset= 0; hdr_page_no= 0; hdr_offset= 0; rw_lock_create(trx_purge_latch_key, &latch, SYNC_PURGE_LATCH); mutex_create(LATCH_ID_PURGE_SYS_PQ, &pq_mutex); truncate.current= NULL; truncate.last= NULL; heap= mem_heap_create(4096); } /** Close the purge subsystem on shutdown. */ void purge_sys_t::close() { ut_ad(this == &purge_sys); if (!heap) return; ut_ad(!enabled()); trx_t* trx = query->trx; que_graph_free(query); ut_ad(!trx->id); ut_ad(trx->state == TRX_STATE_ACTIVE); trx->state= TRX_STATE_NOT_STARTED; trx->free(); rw_lock_free(&latch); mutex_free(&pq_mutex); mem_heap_free(heap); heap= nullptr; } /*================ UNDO LOG HISTORY LIST =============================*/ /** Prepend the history list with an undo log. Remove the undo log segment from the rseg slot if it is too big for reuse. @param[in] trx transaction @param[in,out] undo undo log @param[in,out] mtr mini-transaction */ void trx_purge_add_undo_to_history(const trx_t* trx, trx_undo_t*& undo, mtr_t* mtr) { DBUG_PRINT("trx", ("commit(" TRX_ID_FMT "," TRX_ID_FMT ")", trx->id, trx_id_t{trx->rw_trx_hash_element->no})); ut_ad(undo == trx->rsegs.m_redo.undo); trx_rseg_t* rseg = trx->rsegs.m_redo.rseg; ut_ad(undo->rseg == rseg); buf_block_t* rseg_header = trx_rsegf_get( rseg->space, rseg->page_no, mtr); buf_block_t* undo_page = trx_undo_set_state_at_finish( undo, mtr); trx_ulogf_t* undo_header = undo_page->frame + undo->hdr_offset; ut_ad(mach_read_from_2(undo_header + TRX_UNDO_NEEDS_PURGE) <= 1); if (UNIV_UNLIKELY(mach_read_from_4(TRX_RSEG + TRX_RSEG_FORMAT + rseg_header->frame))) { /* This database must have been upgraded from before MariaDB 10.3.5. */ trx_rseg_format_upgrade(rseg_header, mtr); } if (undo->state != TRX_UNDO_CACHED) { /* The undo log segment will not be reused */ ut_a(undo->id < TRX_RSEG_N_SLOTS); compile_time_assert(FIL_NULL == 0xffffffff); mtr->memset(rseg_header, TRX_RSEG + TRX_RSEG_UNDO_SLOTS + undo->id * TRX_RSEG_SLOT_SIZE, 4, 0xff); MONITOR_DEC(MONITOR_NUM_UNDO_SLOT_USED); uint32_t hist_size = mach_read_from_4(TRX_RSEG_HISTORY_SIZE + TRX_RSEG + rseg_header->frame); ut_ad(undo->size == flst_get_len(TRX_UNDO_SEG_HDR + TRX_UNDO_PAGE_LIST + undo_page->frame)); mtr->write<4>(*rseg_header, TRX_RSEG + TRX_RSEG_HISTORY_SIZE + rseg_header->frame, hist_size + undo->size); mtr->write<8>(*rseg_header, TRX_RSEG + TRX_RSEG_MAX_TRX_ID + rseg_header->frame, trx_sys.get_max_trx_id()); } /* After the purge thread has been given permission to exit, we may roll back transactions (trx->undo_no==0) in THD::cleanup() invoked from unlink_thd() in fast shutdown, or in trx_rollback_recovered() in slow shutdown. Before any transaction-generating background threads or the purge have been started, we can start transactions in row_merge_drop_temp_indexes() and fts_drop_orphaned_tables(), and roll back recovered transactions. Arbitrary user transactions may be executed when all the undo log related background processes (including purge) are disabled due to innodb_force_recovery=2 or innodb_force_recovery=3. DROP TABLE may be executed at any innodb_force_recovery level. During fast shutdown, we may also continue to execute user transactions. */ ut_ad(srv_undo_sources || trx->undo_no == 0 || (!purge_sys.enabled() && (srv_is_being_started || trx_rollback_is_active || srv_force_recovery >= SRV_FORCE_NO_BACKGROUND)) || ((trx->mysql_thd || trx->internal) && srv_fast_shutdown)); #ifdef WITH_WSREP if (wsrep_is_wsrep_xid(trx->xid)) { trx_rseg_update_wsrep_checkpoint(rseg_header, trx->xid, mtr); } #endif if (trx->mysql_log_file_name && *trx->mysql_log_file_name) { /* Update the latest MySQL binlog name and offset info in rollback segment header if MySQL binlogging is on or the database server is a MySQL replication save. */ trx_rseg_update_binlog_offset(rseg_header, trx, mtr); } /* Add the log as the first in the history list */ flst_add_first(rseg_header, TRX_RSEG + TRX_RSEG_HISTORY, undo_page, static_cast(undo->hdr_offset + TRX_UNDO_HISTORY_NODE), mtr); mtr->write<8,mtr_t::MAYBE_NOP>(*undo_page, undo_header + TRX_UNDO_TRX_NO, trx->rw_trx_hash_element->no); mtr->write<2,mtr_t::MAYBE_NOP>(*undo_page, undo_header + TRX_UNDO_NEEDS_PURGE, 1U); if (rseg->last_page_no == FIL_NULL) { rseg->last_page_no = undo->hdr_page_no; rseg->set_last_commit(undo->hdr_offset, trx->rw_trx_hash_element->no); rseg->needs_purge = true; } trx_sys.rseg_history_len++; if (undo->state == TRX_UNDO_CACHED) { UT_LIST_ADD_FIRST(rseg->undo_cached, undo); MONITOR_INC(MONITOR_NUM_UNDO_SLOT_CACHED); } else { ut_ad(undo->state == TRX_UNDO_TO_PURGE); ut_free(undo); } undo = NULL; } /** Remove undo log header from the history list. @param[in,out] rseg rollback segment header page @param[in] log undo log segment header page @param[in] offset byte offset in the undo log segment header page @param[in,out] mtr mini-transaction */ static void trx_purge_remove_log_hdr(buf_block_t *rseg, buf_block_t* log, uint16_t offset, mtr_t *mtr) { flst_remove(rseg, TRX_RSEG + TRX_RSEG_HISTORY, log, static_cast(offset + TRX_UNDO_HISTORY_NODE), mtr); trx_sys.rseg_history_len--; } /** Free an undo log segment, and remove the header from the history list. @param[in,out] rseg rollback segment @param[in] hdr_addr file address of log_hdr */ static void trx_purge_free_segment(trx_rseg_t* rseg, fil_addr_t hdr_addr) { mtr_t mtr; mtr.start(); mutex_enter(&rseg->mutex); buf_block_t* rseg_hdr = trx_rsegf_get(rseg->space, rseg->page_no, &mtr); buf_block_t* block = trx_undo_page_get( page_id_t(rseg->space->id, hdr_addr.page), &mtr); /* Mark the last undo log totally purged, so that if the system crashes, the tail of the undo log will not get accessed again. The list of pages in the undo log tail gets inconsistent during the freeing of the segment, and therefore purge should not try to access them again. */ mtr.write<2,mtr_t::MAYBE_NOP>(*block, block->frame + hdr_addr.boffset + TRX_UNDO_NEEDS_PURGE, 0U); while (!fseg_free_step_not_header( TRX_UNDO_SEG_HDR + TRX_UNDO_FSEG_HEADER + block->frame, &mtr)) { mutex_exit(&rseg->mutex); mtr.commit(); mtr.start(); mutex_enter(&rseg->mutex); rseg_hdr = trx_rsegf_get(rseg->space, rseg->page_no, &mtr); block = trx_undo_page_get( page_id_t(rseg->space->id, hdr_addr.page), &mtr); } /* The page list may now be inconsistent, but the length field stored in the list base node tells us how big it was before we started the freeing. */ const uint32_t seg_size = flst_get_len( TRX_UNDO_SEG_HDR + TRX_UNDO_PAGE_LIST + block->frame); /* We may free the undo log segment header page; it must be freed within the same mtr as the undo log header is removed from the history list: otherwise, in case of a database crash, the segment could become inaccessible garbage in the file space. */ trx_purge_remove_log_hdr(rseg_hdr, block, hdr_addr.boffset, &mtr); do { /* Here we assume that a file segment with just the header page can be freed in a few steps, so that the buffer pool is not flooded with bufferfixed pages: see the note in fsp0fsp.cc. */ } while (!fseg_free_step(TRX_UNDO_SEG_HDR + TRX_UNDO_FSEG_HEADER + block->frame, &mtr)); byte* hist = TRX_RSEG + TRX_RSEG_HISTORY_SIZE + rseg_hdr->frame; ut_ad(mach_read_from_4(hist) >= seg_size); mtr.write<4>(*rseg_hdr, hist, mach_read_from_4(hist) - seg_size); ut_ad(rseg->curr_size >= seg_size); rseg->curr_size -= seg_size; mutex_exit(&(rseg->mutex)); mtr_commit(&mtr); } /** Remove unnecessary history data from a rollback segment. @param[in,out] rseg rollback segment @param[in] limit truncate anything before this */ static void trx_purge_truncate_rseg_history( trx_rseg_t& rseg, const purge_sys_t::iterator& limit) { fil_addr_t hdr_addr; fil_addr_t prev_hdr_addr; mtr_t mtr; trx_id_t undo_trx_no; mtr.start(); ut_ad(rseg.is_persistent()); mutex_enter(&rseg.mutex); buf_block_t* rseg_hdr = trx_rsegf_get(rseg.space, rseg.page_no, &mtr); hdr_addr = flst_get_last(TRX_RSEG + TRX_RSEG_HISTORY + rseg_hdr->frame); hdr_addr.boffset = static_cast(hdr_addr.boffset - TRX_UNDO_HISTORY_NODE); loop: if (hdr_addr.page == FIL_NULL) { func_exit: mutex_exit(&rseg.mutex); mtr.commit(); return; } buf_block_t* block = trx_undo_page_get(page_id_t(rseg.space->id, hdr_addr.page), &mtr); undo_trx_no = mach_read_from_8(block->frame + hdr_addr.boffset + TRX_UNDO_TRX_NO); if (undo_trx_no >= limit.trx_no) { if (undo_trx_no == limit.trx_no) { trx_undo_truncate_start( &rseg, hdr_addr.page, hdr_addr.boffset, limit.undo_no); } goto func_exit; } prev_hdr_addr = flst_get_prev_addr(block->frame + hdr_addr.boffset + TRX_UNDO_HISTORY_NODE); prev_hdr_addr.boffset = static_cast(prev_hdr_addr.boffset - TRX_UNDO_HISTORY_NODE); if (mach_read_from_2(TRX_UNDO_SEG_HDR + TRX_UNDO_STATE + block->frame) == TRX_UNDO_TO_PURGE && !mach_read_from_2(block->frame + hdr_addr.boffset + TRX_UNDO_NEXT_LOG)) { /* We can free the whole log segment */ mutex_exit(&rseg.mutex); mtr.commit(); /* calls the trx_purge_remove_log_hdr() inside trx_purge_free_segment(). */ trx_purge_free_segment(&rseg, hdr_addr); } else { /* Remove the log hdr from the rseg history. */ trx_purge_remove_log_hdr(rseg_hdr, block, hdr_addr.boffset, &mtr); mutex_exit(&rseg.mutex); mtr.commit(); } mtr.start(); mutex_enter(&rseg.mutex); rseg_hdr = trx_rsegf_get(rseg.space, rseg.page_no, &mtr); hdr_addr = prev_hdr_addr; goto loop; } /** Cleanse purge queue to remove the rseg that reside in undo-tablespace marked for truncate. @param[in] space undo tablespace being truncated */ static void trx_purge_cleanse_purge_queue(const fil_space_t& space) { typedef std::vector purge_elem_list_t; purge_elem_list_t purge_elem_list; mutex_enter(&purge_sys.pq_mutex); /* Remove rseg instances that are in the purge queue before we start truncate of corresponding UNDO truncate. */ while (!purge_sys.purge_queue.empty()) { purge_elem_list.push_back(purge_sys.purge_queue.top()); purge_sys.purge_queue.pop(); } for (purge_elem_list_t::iterator it = purge_elem_list.begin(); it != purge_elem_list.end(); ++it) { for (TrxUndoRsegs::iterator it2 = it->begin(); it2 != it->end(); ++it2) { if ((*it2)->space == &space) { it->erase(it2); break; } } if (!it->empty()) { purge_sys.purge_queue.push(*it); } } mutex_exit(&purge_sys.pq_mutex); } /** Removes unnecessary history data from rollback segments. NOTE that when this function is called, the caller must not have any latches on undo log pages! */ static void trx_purge_truncate_history() { ut_ad(purge_sys.head <= purge_sys.tail); purge_sys_t::iterator& head = purge_sys.head.trx_no ? purge_sys.head : purge_sys.tail; if (head.trx_no >= purge_sys.low_limit_no()) { /* This is sometimes necessary. TODO: find out why. */ head.trx_no = purge_sys.low_limit_no(); head.undo_no = 0; } for (ulint i = 0; i < TRX_SYS_N_RSEGS; ++i) { if (trx_rseg_t* rseg = trx_sys.rseg_array[i]) { ut_ad(rseg->id == i); trx_purge_truncate_rseg_history(*rseg, head); } } if (srv_undo_tablespaces_active < 2) { return; } while (srv_undo_log_truncate) { if (!purge_sys.truncate.current) { const ulint threshold = ulint(srv_max_undo_log_size >> srv_page_size_shift); for (ulint i = purge_sys.truncate.last ? purge_sys.truncate.last->id - srv_undo_space_id_start : 0, j = i;; ) { ulint space_id = srv_undo_space_id_start + i; ut_ad(srv_is_undo_tablespace(space_id)); fil_space_t* space= fil_space_get(space_id); if (space && space->get_size() > threshold) { purge_sys.truncate.current = space; break; } ++i; i %= srv_undo_tablespaces_active; if (i == j) { break; } } } if (!purge_sys.truncate.current) { return; } fil_space_t& space = *purge_sys.truncate.current; /* Undo tablespace always are a single file. */ ut_a(UT_LIST_GET_LEN(space.chain) == 1); fil_node_t* file = UT_LIST_GET_FIRST(space.chain); /* The undo tablespace files are never closed. */ ut_ad(file->is_open()); DBUG_LOG("undo", "marking for truncate: " << file->name); for (ulint i = 0; i < TRX_SYS_N_RSEGS; ++i) { if (trx_rseg_t* rseg = trx_sys.rseg_array[i]) { ut_ad(rseg->is_persistent()); if (rseg->space == &space) { /* Once set, this rseg will not be allocated to subsequent transactions, but we will wait for existing active transactions to finish. */ rseg->skip_allocation = true; } } } for (ulint i = 0; i < TRX_SYS_N_RSEGS; ++i) { trx_rseg_t* rseg = trx_sys.rseg_array[i]; if (!rseg || rseg->space != &space) { continue; } mutex_enter(&rseg->mutex); ut_ad(rseg->skip_allocation); if (rseg->trx_ref_count) { not_free: mutex_exit(&rseg->mutex); return; } if (rseg->curr_size != 1) { /* Check if all segments are cached and safe to remove. */ ulint cached = 0; for (trx_undo_t* undo = UT_LIST_GET_FIRST( rseg->undo_cached); undo; undo = UT_LIST_GET_NEXT(undo_list, undo)) { if (head.trx_no < undo->trx_id) { goto not_free; } else { cached += undo->size; } } ut_ad(rseg->curr_size > cached); if (rseg->curr_size > cached + 1) { goto not_free; } } mutex_exit(&rseg->mutex); } ib::info() << "Truncating " << file->name; trx_purge_cleanse_purge_queue(space); /* Flush all to-be-discarded pages of the tablespace. During truncation, we do not want any writes to the to-be-discarded area, because we must set the space.size early in order to have deterministic page allocation. If a log checkpoint was completed at LSN earlier than our mini-transaction commit and the server was killed, then discarding the to-be-trimmed pages without flushing would break crash recovery. So, we cannot avoid the write. */ while (buf_flush_list_space(&space)); log_free_check(); /* Adjust the tablespace metadata. */ if (!fil_truncate_prepare(space.id)) { ib::error() << "Failed to find UNDO tablespace " << file->name; return; } /* Re-initialize tablespace, in a single mini-transaction. */ mtr_t mtr; const ulint size = SRV_UNDO_TABLESPACE_SIZE_IN_PAGES; mtr.start(); mtr_x_lock_space(purge_sys.truncate.current, &mtr); /* Associate the undo tablespace with mtr. During mtr::commit(), InnoDB can use the undo tablespace object to clear all freed ranges */ mtr.set_named_space(purge_sys.truncate.current); mtr.trim_pages(page_id_t(space.id, size)); fsp_header_init(purge_sys.truncate.current, size, &mtr); mutex_enter(&fil_system.mutex); purge_sys.truncate.current->size = file->size = size; mutex_exit(&fil_system.mutex); buf_block_t* sys_header = trx_sysf_get(&mtr); for (ulint i = 0; i < TRX_SYS_N_RSEGS; ++i) { trx_rseg_t* rseg = trx_sys.rseg_array[i]; if (!rseg || rseg->space != &space) { continue; } ut_ad(rseg->is_persistent()); ut_d(const ulint old_page = rseg->page_no); buf_block_t* rblock = trx_rseg_header_create( purge_sys.truncate.current, rseg->id, sys_header, &mtr); ut_ad(rblock); rseg->page_no = rblock ? rblock->page.id().page_no() : FIL_NULL; ut_ad(old_page == rseg->page_no); /* Before re-initialization ensure that we free the existing structure. There can't be any active transactions. */ ut_a(UT_LIST_GET_LEN(rseg->undo_list) == 0); trx_undo_t* next_undo; for (trx_undo_t* undo = UT_LIST_GET_FIRST( rseg->undo_cached); undo; undo = next_undo) { next_undo = UT_LIST_GET_NEXT(undo_list, undo); UT_LIST_REMOVE(rseg->undo_cached, undo); MONITOR_DEC(MONITOR_NUM_UNDO_SLOT_CACHED); ut_free(undo); } UT_LIST_INIT(rseg->undo_list, &trx_undo_t::undo_list); UT_LIST_INIT(rseg->undo_cached, &trx_undo_t::undo_list); /* These were written by trx_rseg_header_create(). */ ut_ad(!mach_read_from_4(TRX_RSEG + TRX_RSEG_FORMAT + rblock->frame)); ut_ad(!mach_read_from_4(TRX_RSEG + TRX_RSEG_HISTORY_SIZE + rblock->frame)); /* Initialize the undo log lists according to the rseg header */ rseg->curr_size = 1; rseg->trx_ref_count = 0; rseg->last_page_no = FIL_NULL; rseg->last_commit_and_offset = 0; rseg->needs_purge = false; } mtr.commit(); /* Write-ahead the redo log record. */ log_write_up_to(mtr.commit_lsn(), true); /* Trim the file size. */ os_file_truncate(file->name, file->handle, os_offset_t(size) << srv_page_size_shift, true); /* This is only executed by srv_purge_coordinator_thread. */ export_vars.innodb_undo_truncations++; /* In MDEV-8319 (10.5) we will PUNCH_HOLE the garbage (with write-ahead logging). */ mutex_enter(&fil_system.mutex); ut_ad(&space == purge_sys.truncate.current); ut_ad(space.is_being_truncated); purge_sys.truncate.current->set_stopping(false); purge_sys.truncate.current->is_being_truncated = false; mutex_exit(&fil_system.mutex); if (purge_sys.rseg != NULL && purge_sys.rseg->last_page_no == FIL_NULL) { /* If purge_sys.rseg is pointing to rseg that was recently truncated then move to next rseg element. Note: Ideally purge_sys.rseg should be NULL because purge should complete processing of all the records but there is purge_batch_size that can force the purge loop to exit before all the records are purged and in this case purge_sys.rseg could point to a valid rseg waiting for next purge cycle. */ purge_sys.next_stored = false; purge_sys.rseg = NULL; } DBUG_EXECUTE_IF("ib_undo_trunc", ib::info() << "ib_undo_trunc"; log_buffer_flush_to_disk(); DBUG_SUICIDE();); for (ulint i = 0; i < TRX_SYS_N_RSEGS; ++i) { if (trx_rseg_t* rseg = trx_sys.rseg_array[i]) { ut_ad(rseg->is_persistent()); if (rseg->space == &space) { rseg->skip_allocation = false; } } } ib::info() << "Truncated " << file->name; purge_sys.truncate.last = purge_sys.truncate.current; purge_sys.truncate.current = NULL; } } /***********************************************************************//** Updates the last not yet purged history log info in rseg when we have purged a whole undo log. Advances also purge_sys.purge_trx_no past the purged log. */ static void trx_purge_rseg_get_next_history_log( ulint* n_pages_handled)/*!< in/out: number of UNDO pages handled */ { fil_addr_t prev_log_addr; trx_id_t trx_no; mtr_t mtr; mutex_enter(&purge_sys.rseg->mutex); ut_a(purge_sys.rseg->last_page_no != FIL_NULL); purge_sys.tail.trx_no = purge_sys.rseg->last_trx_no() + 1; purge_sys.tail.undo_no = 0; purge_sys.next_stored = false; mtr.start(); const buf_block_t* undo_page = trx_undo_page_get_s_latched( page_id_t(purge_sys.rseg->space->id, purge_sys.rseg->last_page_no), &mtr); const trx_ulogf_t* log_hdr = undo_page->frame + purge_sys.rseg->last_offset(); /* Increase the purge page count by one for every handled log */ (*n_pages_handled)++; prev_log_addr = flst_get_prev_addr(log_hdr + TRX_UNDO_HISTORY_NODE); prev_log_addr.boffset = static_cast(prev_log_addr.boffset - TRX_UNDO_HISTORY_NODE); const bool empty = prev_log_addr.page == FIL_NULL; if (empty) { /* No logs left in the history list */ purge_sys.rseg->last_page_no = FIL_NULL; } mutex_exit(&purge_sys.rseg->mutex); mtr.commit(); if (empty) { return; } /* Read the previous log header. */ mtr.start(); log_hdr = trx_undo_page_get_s_latched( page_id_t(purge_sys.rseg->space->id, prev_log_addr.page), &mtr)->frame + prev_log_addr.boffset; trx_no = mach_read_from_8(log_hdr + TRX_UNDO_TRX_NO); ut_ad(mach_read_from_2(log_hdr + TRX_UNDO_NEEDS_PURGE) <= 1); mtr_commit(&mtr); mutex_enter(&purge_sys.rseg->mutex); purge_sys.rseg->last_page_no = prev_log_addr.page; purge_sys.rseg->set_last_commit(prev_log_addr.boffset, trx_no); purge_sys.rseg->needs_purge = log_hdr[TRX_UNDO_NEEDS_PURGE + 1] != 0; /* Purge can also produce events, however these are already ordered in the rollback segment and any user generated event will be greater than the events that Purge produces. ie. Purge can never produce events from an empty rollback segment. */ mutex_enter(&purge_sys.pq_mutex); purge_sys.purge_queue.push(*purge_sys.rseg); mutex_exit(&purge_sys.pq_mutex); mutex_exit(&purge_sys.rseg->mutex); } /** Position the purge sys "iterator" on the undo record to use for purging. */ static void trx_purge_read_undo_rec() { uint16_t offset; uint32_t page_no; ib_uint64_t undo_no; purge_sys.hdr_offset = purge_sys.rseg->last_offset(); page_no = purge_sys.hdr_page_no = purge_sys.rseg->last_page_no; if (purge_sys.rseg->needs_purge) { mtr_t mtr; mtr.start(); buf_block_t* undo_page; if (trx_undo_rec_t* undo_rec = trx_undo_get_first_rec( *purge_sys.rseg->space, purge_sys.hdr_page_no, purge_sys.hdr_offset, RW_S_LATCH, undo_page, &mtr)) { offset = page_offset(undo_rec); undo_no = trx_undo_rec_get_undo_no(undo_rec); page_no = undo_page->page.id().page_no(); } else { offset = 0; undo_no = 0; } mtr.commit(); } else { offset = 0; undo_no = 0; } purge_sys.offset = offset; purge_sys.page_no = page_no; purge_sys.tail.undo_no = undo_no; purge_sys.next_stored = true; } /***********************************************************************//** Chooses the next undo log to purge and updates the info in purge_sys. This function is used to initialize purge_sys when the next record to purge is not known, and also to update the purge system info on the next record when purge has handled the whole undo log for a transaction. */ static void trx_purge_choose_next_log(void) /*===========================*/ { ut_ad(!purge_sys.next_stored); if (purge_sys.rseg_iter.set_next()) { trx_purge_read_undo_rec(); } else { /* There is nothing to do yet. */ os_thread_yield(); } } /***********************************************************************//** Gets the next record to purge and updates the info in the purge system. @return copy of an undo log record or pointer to the dummy undo log record */ static trx_undo_rec_t* trx_purge_get_next_rec( /*===================*/ ulint* n_pages_handled,/*!< in/out: number of UNDO pages handled */ mem_heap_t* heap) /*!< in: memory heap where copied */ { mtr_t mtr; ut_ad(purge_sys.next_stored); ut_ad(purge_sys.tail.trx_no < purge_sys.low_limit_no()); const ulint space = purge_sys.rseg->space->id; const uint32_t page_no = purge_sys.page_no; const uint16_t offset = purge_sys.offset; if (offset == 0) { /* It is the dummy undo log record, which means that there is no need to purge this undo log */ trx_purge_rseg_get_next_history_log(n_pages_handled); /* Look for the next undo log and record to purge */ trx_purge_choose_next_log(); return(&trx_purge_dummy_rec); } mtr_start(&mtr); buf_block_t* undo_page = trx_undo_page_get_s_latched( page_id_t(space, page_no), &mtr); buf_block_t* rec2_page = undo_page; const trx_undo_rec_t* rec2 = trx_undo_page_get_next_rec( undo_page, offset, purge_sys.hdr_page_no, purge_sys.hdr_offset); if (rec2 == NULL) { rec2 = trx_undo_get_next_rec(rec2_page, offset, purge_sys.hdr_page_no, purge_sys.hdr_offset, &mtr); } if (rec2 == NULL) { mtr_commit(&mtr); trx_purge_rseg_get_next_history_log(n_pages_handled); /* Look for the next undo log and record to purge */ trx_purge_choose_next_log(); mtr_start(&mtr); undo_page = trx_undo_page_get_s_latched( page_id_t(space, page_no), &mtr); } else { purge_sys.offset = page_offset(rec2); purge_sys.page_no = rec2_page->page.id().page_no(); purge_sys.tail.undo_no = trx_undo_rec_get_undo_no(rec2); if (undo_page != rec2_page) { /* We advance to a new page of the undo log: */ (*n_pages_handled)++; } } trx_undo_rec_t* rec_copy = trx_undo_rec_copy(undo_page->frame + offset, heap); mtr_commit(&mtr); return(rec_copy); } /********************************************************************//** Fetches the next undo log record from the history list to purge. It must be released with the corresponding release function. @return copy of an undo log record or pointer to trx_purge_dummy_rec, if the whole undo log can skipped in purge; NULL if none left */ static MY_ATTRIBUTE((warn_unused_result)) trx_undo_rec_t* trx_purge_fetch_next_rec( /*=====================*/ roll_ptr_t* roll_ptr, /*!< out: roll pointer to undo record */ ulint* n_pages_handled,/*!< in/out: number of UNDO log pages handled */ mem_heap_t* heap) /*!< in: memory heap where copied */ { if (!purge_sys.next_stored) { trx_purge_choose_next_log(); if (!purge_sys.next_stored) { DBUG_PRINT("ib_purge", ("no logs left in the history list")); return(NULL); } } if (purge_sys.tail.trx_no >= purge_sys.low_limit_no()) { return(NULL); } /* fprintf(stderr, "Thread %lu purging trx %llu undo record %llu\n", os_thread_get_curr_id(), iter->trx_no, iter->undo_no); */ *roll_ptr = trx_undo_build_roll_ptr( /* row_purge_record_func() will later set ROLL_PTR_INSERT_FLAG for TRX_UNDO_INSERT_REC */ false, purge_sys.rseg->id, purge_sys.page_no, purge_sys.offset); /* The following call will advance the stored values of the purge iterator. */ return(trx_purge_get_next_rec(n_pages_handled, heap)); } /** Run a purge batch. @param n_purge_threads number of purge threads @return number of undo log pages handled in the batch */ static ulint trx_purge_attach_undo_recs(ulint n_purge_threads) { que_thr_t* thr; ulint i; ulint n_pages_handled = 0; ulint n_thrs = UT_LIST_GET_LEN(purge_sys.query->thrs); ut_a(n_purge_threads > 0); purge_sys.head = purge_sys.tail; #ifdef UNIV_DEBUG i = 0; /* Debug code to validate some pre-requisites and reset done flag. */ for (thr = UT_LIST_GET_FIRST(purge_sys.query->thrs); thr != NULL && i < n_purge_threads; thr = UT_LIST_GET_NEXT(thrs, thr), ++i) { purge_node_t* node; /* Get the purge node. */ node = (purge_node_t*) thr->child; ut_ad(que_node_get_type(node) == QUE_NODE_PURGE); ut_ad(node->undo_recs.empty()); ut_ad(!node->in_progress); ut_d(node->in_progress = true); } /* There should never be fewer nodes than threads, the inverse however is allowed because we only use purge threads as needed. */ ut_ad(i == n_purge_threads); #endif /* Fetch and parse the UNDO records. The UNDO records are added to a per purge node vector. */ thr = UT_LIST_GET_FIRST(purge_sys.query->thrs); ut_a(n_thrs > 0 && thr != NULL); ut_ad(purge_sys.head <= purge_sys.tail); i = 0; const ulint batch_size = srv_purge_batch_size; std::unordered_map table_id_map; mem_heap_empty(purge_sys.heap); while (UNIV_LIKELY(srv_undo_sources) || !srv_fast_shutdown) { purge_node_t* node; trx_purge_rec_t purge_rec; ut_a(!thr->is_active); /* Get the purge node. */ node = (purge_node_t*) thr->child; ut_a(que_node_get_type(node) == QUE_NODE_PURGE); /* Track the max {trx_id, undo_no} for truncating the UNDO logs once we have purged the records. */ if (purge_sys.head <= purge_sys.tail) { purge_sys.head = purge_sys.tail; } /* Fetch the next record, and advance the purge_sys.tail. */ purge_rec.undo_rec = trx_purge_fetch_next_rec( &purge_rec.roll_ptr, &n_pages_handled, purge_sys.heap); if (purge_rec.undo_rec == NULL) { break; } else if (purge_rec.undo_rec == &trx_purge_dummy_rec) { continue; } table_id_t table_id = trx_undo_rec_get_table_id( purge_rec.undo_rec); purge_node_t *& table_node = table_id_map[table_id]; if (table_node) { node = table_node; } else { thr = UT_LIST_GET_NEXT(thrs, thr); if (!(++i % n_purge_threads)) { thr = UT_LIST_GET_FIRST( purge_sys.query->thrs); } ut_a(thr != NULL); table_node = node; } node->undo_recs.push(purge_rec); if (n_pages_handled >= batch_size) { break; } } ut_ad(purge_sys.head <= purge_sys.tail); return(n_pages_handled); } /*******************************************************************//** Calculate the DML delay required. @return delay in microseconds or ULINT_MAX */ static ulint trx_purge_dml_delay(void) /*=====================*/ { /* Determine how much data manipulation language (DML) statements need to be delayed in order to reduce the lagging of the purge thread. */ ulint delay = 0; /* in microseconds; default: no delay */ /* If purge lag is set then calculate the new DML delay. */ if (srv_max_purge_lag > 0) { double ratio = static_cast(trx_sys.rseg_history_len) / static_cast(srv_max_purge_lag); if (ratio > 1.0) { /* If the history list length exceeds the srv_max_purge_lag, the data manipulation statements are delayed by at least 5000 microseconds. */ delay = (ulint) ((ratio - .5) * 10000); } if (delay > srv_max_purge_lag_delay) { delay = srv_max_purge_lag_delay; } MONITOR_SET(MONITOR_DML_PURGE_DELAY, delay); } return(delay); } extern tpool::waitable_task purge_worker_task; /** Wait for pending purge jobs to complete. */ static void trx_purge_wait_for_workers_to_complete() { bool notify_wait = purge_worker_task.is_running(); if (notify_wait) tpool::tpool_wait_begin(); purge_worker_task.wait(); if(notify_wait) tpool::tpool_wait_end(); /* There should be no outstanding tasks as long as the worker threads are active. */ ut_ad(srv_get_task_queue_length() == 0); } /** Run a purge batch. @param n_tasks number of purge tasks to submit to the queue @param truncate whether to truncate the history at the end of the batch @return number of undo log pages handled in the batch */ ulint trx_purge(ulint n_tasks, bool truncate) { que_thr_t* thr = NULL; ulint n_pages_handled; ut_ad(n_tasks > 0); srv_dml_needed_delay = trx_purge_dml_delay(); purge_sys.clone_oldest_view(); #ifdef UNIV_DEBUG if (srv_purge_view_update_only_debug) { return(0); } #endif /* UNIV_DEBUG */ /* Fetch the UNDO recs that need to be purged. */ n_pages_handled = trx_purge_attach_undo_recs(n_tasks); /* Submit tasks to workers queue if using multi-threaded purge. */ for (ulint i = n_tasks; --i; ) { thr = que_fork_scheduler_round_robin(purge_sys.query, thr); ut_a(thr); srv_que_task_enqueue_low(thr); srv_thread_pool->submit_task(&purge_worker_task); } thr = que_fork_scheduler_round_robin(purge_sys.query, thr); que_run_threads(thr); trx_purge_wait_for_workers_to_complete(); if (truncate) { trx_purge_truncate_history(); } MONITOR_INC_VALUE(MONITOR_PURGE_INVOKED, 1); MONITOR_INC_VALUE(MONITOR_PURGE_N_PAGE_HANDLED, n_pages_handled); return(n_pages_handled); }