mariadb/storage/innobase/include/row0vers.h

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/*****************************************************************************
Copyright (c) 1997, 2016, Oracle and/or its affiliates. All Rights Reserved.
Copyright (c) 2017, 2019, 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
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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.,
2019-05-11 19:25:02 +03:00
51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA
*****************************************************************************/
/**************************************************//**
@file include/row0vers.h
Row versions
Created 2/6/1997 Heikki Tuuri
*******************************************************/
#ifndef row0vers_h
#define row0vers_h
#include "data0data.h"
#include "trx0types.h"
#include "que0types.h"
#include "rem0types.h"
#include "mtr0mtr.h"
#include "dict0mem.h"
#include "row0types.h"
// Forward declaration
class ReadView;
/** Determine if an active transaction has inserted or modified a secondary
index record.
MDEV-14638 - Replace trx_sys_t::rw_trx_set with LF_HASH trx_sys_t::rw_trx_set is implemented as std::set, which does a few quite expensive operations under trx_sys_t::mutex protection: e.g. malloc/free when adding/removing elements. Traversing b-tree is not that cheap either. This has negative scalability impact, which is especially visible when running oltp_update_index.lua benchmark on a ramdisk. To reduce trx_sys_t::mutex contention std::set is replaced with LF_HASH. None of LF_HASH operations require trx_sys_t::mutex (nor any other global mutex) protection. Another interesting issue observed with std::set is reproducible ~2% performance decline after benchmark is ran for ~60 seconds. With LF_HASH results are stable. All in all this patch optimises away one of three trx_sys->mutex locks per oltp_update_index.lua query. The other two critical sections became smaller. Relevant clean-ups: Replaced rw_trx_set iteration at startup with local set. The latter is needed because values inserted to rw_trx_list must be ordered by trx->id. Removed redundant conditions from trx_reference(): it is (and even was) never called with transactions that have trx->state == TRX_STATE_COMMITTED_IN_MEMORY. do_ref_count doesn't (and probably even didn't) make any sense: now it is called only when reference counter increment is actually requested. Moved condition out of mutex in trx_erase_lists(). trx_rw_is_active(), trx_rw_is_active_low() and trx_get_rw_trx_by_id() were greatly simplified and replaced by appropriate trx_rw_hash_t methods. Compared to rw_trx_set, rw_trx_hash holds transactions only in PREPARED or ACTIVE states. Transactions in COMMITTED state were required to be found at InnoDB startup only. They are now looked up in the local set. Removed unused trx_assert_recovered(). Removed unused innobase_get_trx() declaration. Removed rather semantically incorrect trx_sys_rw_trx_add(). Moved information printout from trx_sys_init_at_db_start() to trx_lists_init_at_db_start().
2017-12-13 15:40:41 +04:00
@param[in,out] caller_trx trx of current thread
@param[in] rec secondary index record
@param[in] index secondary index
@param[in] offsets rec_get_offsets(rec, index)
MDEV-15326: InnoDB: Failing assertion: !other_lock MySQL 5.7.9 (and MariaDB 10.2.2) introduced a race condition between InnoDB transaction commit and the conversion of implicit locks into explicit ones. The assertion failure can be triggered with a test that runs 3 concurrent single-statement transactions in a loop on a simple table: CREATE TABLE t (a INT PRIMARY KEY) ENGINE=InnoDB; thread1: INSERT INTO t SET a=1; thread2: DELETE FROM t; thread3: SELECT * FROM t FOR UPDATE; -- or DELETE FROM t; The failure scenarios are like the following: (1) The INSERT statement is being committed, waiting for lock_sys->mutex. (2) At the time of the failure, both the DELETE and SELECT transactions are active but have not logged any changes yet. (3) The transaction where the !other_lock assertion fails started lock_rec_convert_impl_to_expl(). (4) After this point, the commit of the INSERT removed the transaction from trx_sys->rw_trx_set, in trx_erase_lists(). (5) The other transaction consulted trx_sys->rw_trx_set and determined that there is no implicit lock. Hence, it grabbed the lock. (6) The !other_lock assertion fails in lock_rec_add_to_queue() for the lock_rec_convert_impl_to_expl(), because the lock was 'stolen'. This assertion failure looks genuine, because the INSERT transaction is still active (trx->state=TRX_STATE_ACTIVE). The problematic step (4) was introduced in mysql/mysql-server@e27e0e0bb75b4d35e87059816f1cc370c09890ad which fixed something related to MVCC (covered by the test innodb.innodb-read-view). Basically, it reintroduced an error that had been mentioned in an earlier commit mysql/mysql-server@a17be6963fc0d9210fa0642d3985b7219cdaf0c5: "The active transaction was removed from trx_sys->rw_trx_set prematurely." Our fix goes along the following lines: (a) Implicit locks will released by assigning trx->state=TRX_STATE_COMMITTED_IN_MEMORY as the first step. This transition will no longer be protected by lock_sys_t::mutex, only by trx->mutex. This idea is by Sergey Vojtovich. (b) We detach the transaction from trx_sys before starting to release explicit locks. (c) All callers of trx_rw_is_active() and trx_rw_is_active_low() must recheck trx->state after acquiring trx->mutex. (d) Before releasing any explicit locks, we will ensure that any activity by other threads to convert implicit locks into explicit will have ceased, by checking !trx_is_referenced(trx). There was a glitch in this check when it was part of lock_trx_release_locks(); at the end we would release trx->mutex and acquire lock_sys->mutex and trx->mutex, and fail to recheck (trx_is_referenced() is protected by trx_t::mutex). (e) Explicit locks can be released in batches (LOCK_RELEASE_INTERVAL=1000) just like we did before. trx_t::state: Document that the transition to COMMITTED is only protected by trx_t::mutex, no longer by lock_sys_t::mutex. trx_rw_is_active_low(), trx_rw_is_active(): Document that the transaction state should be rechecked after acquiring trx_t::mutex. trx_t::commit_state(): New function to change a transaction to committed state, to release implicit locks. trx_t::release_locks(): New function to release the explicit locks after commit_state(). lock_trx_release_locks(): Move much of the logic to the caller (which must invoke trx_t::commit_state() and trx_t::release_locks() as needed), and assert that the transaction will have locks. trx_get_trx_by_xid(): Make the parameter a pointer to const. lock_rec_other_trx_holds_expl(): Recheck trx->state after acquiring trx->mutex, and avoid a redundant lookup of the transaction. lock_rec_queue_validate(): Recheck impl_trx->state while holding impl_trx->mutex. row_vers_impl_x_locked(), row_vers_impl_x_locked_low(): Document that the transaction state must be rechecked after trx_mutex_enter(). trx_free_prepared(): Adjust for the changes to lock_trx_release_locks().
2019-09-03 12:31:37 +03:00
@return the active transaction; state must be rechecked after
trx_mutex_enter(), and trx->release_reference() must be invoked
@retval NULL if the record was committed */
trx_t*
row_vers_impl_x_locked(
MDEV-14638 - Replace trx_sys_t::rw_trx_set with LF_HASH trx_sys_t::rw_trx_set is implemented as std::set, which does a few quite expensive operations under trx_sys_t::mutex protection: e.g. malloc/free when adding/removing elements. Traversing b-tree is not that cheap either. This has negative scalability impact, which is especially visible when running oltp_update_index.lua benchmark on a ramdisk. To reduce trx_sys_t::mutex contention std::set is replaced with LF_HASH. None of LF_HASH operations require trx_sys_t::mutex (nor any other global mutex) protection. Another interesting issue observed with std::set is reproducible ~2% performance decline after benchmark is ran for ~60 seconds. With LF_HASH results are stable. All in all this patch optimises away one of three trx_sys->mutex locks per oltp_update_index.lua query. The other two critical sections became smaller. Relevant clean-ups: Replaced rw_trx_set iteration at startup with local set. The latter is needed because values inserted to rw_trx_list must be ordered by trx->id. Removed redundant conditions from trx_reference(): it is (and even was) never called with transactions that have trx->state == TRX_STATE_COMMITTED_IN_MEMORY. do_ref_count doesn't (and probably even didn't) make any sense: now it is called only when reference counter increment is actually requested. Moved condition out of mutex in trx_erase_lists(). trx_rw_is_active(), trx_rw_is_active_low() and trx_get_rw_trx_by_id() were greatly simplified and replaced by appropriate trx_rw_hash_t methods. Compared to rw_trx_set, rw_trx_hash holds transactions only in PREPARED or ACTIVE states. Transactions in COMMITTED state were required to be found at InnoDB startup only. They are now looked up in the local set. Removed unused trx_assert_recovered(). Removed unused innobase_get_trx() declaration. Removed rather semantically incorrect trx_sys_rw_trx_add(). Moved information printout from trx_sys_init_at_db_start() to trx_lists_init_at_db_start().
2017-12-13 15:40:41 +04:00
trx_t* caller_trx,
const rec_t* rec,
dict_index_t* index,
const rec_offs* offsets);
/** Finds out if a version of the record, where the version >= the current
purge view, should have ientry as its secondary index entry. We check
if there is any not delete marked version of the record where the trx
id >= purge view, and the secondary index entry == ientry; exactly in
this case we return TRUE.
@param[in] also_curr TRUE if also rec is included in the versions
to search; otherwise only versions prior
to it are searched
@param[in] rec record in the clustered index; the caller
must have a latch on the page
@param[in] mtr mtr holding the latch on rec; it will
also hold the latch on purge_view
@param[in] index secondary index
@param[in] ientry secondary index entry
@param[in] roll_ptr roll_ptr for the purge record
@param[in] trx_id transaction ID on the purging record
@return TRUE if earlier version should have */
bool
row_vers_old_has_index_entry(
bool also_curr,
const rec_t* rec,
mtr_t* mtr,
dict_index_t* index,
const dtuple_t* ientry,
roll_ptr_t roll_ptr,
MDEV-16678 Prefer MDL to dict_sys.latch for innodb background tasks This is joint work with Thirunarayanan Balathandayuthapani. The MDL interface between InnoDB and the rest of the server (in storage/innobase/dict/dict0dict.cc and in include/) is my work, while most everything else is Thiru's. The collection of InnoDB persistent statistics and the defragmentation were not refactored to use MDL. They will keep relying on lower-level interlocking with fil_check_pending_operations(). The purge of transaction history and the background operations on fulltext indexes will use MDL. We will revert commit 2c4844c9e76427525e8c39a2d72686085efe89c3 (MDEV-17813) because thanks to MDL, purge cannot conflict with DDL operations anymore. For a similar reason, we will remove the MDEV-16222 test case from gcol.innodb_virtual_debug_purge. Purge is essentially replacing all use of the global dict_sys.latch with MDL. Purge will skip the undo log records for tables whose names start with #sql-ib or #sql2. Theoretically, such tables might be renamed back to visible table names if TRUNCATE fails to create a new table, or the final rename in ALTER TABLE...ALGORITHM=COPY fails. In that case, purge could permanently leave some garbage in the table. Such garbage will be tolerated; the table would not be considered corrupted. To avoid repeated MDL releases and acquisitions, trx_purge_attach_undo_recs() will sort undo log records by table_id, and purge_node_t will keep the MDL and table handle open for multiple successive undo log records. get_purge_table(): A new accessor, used during the purge of history for indexed virtual columns. This interface should ideally not exist at all. thd_mdl_context(): Accessor of THD::mdl_context. Wrapped in a new thd_mdl_service. dict_get_db_name_len(): Define inline. dict_acquire_mdl_shared(): Acquire explicit shared MDL on a table name if needed. dict_table_open_on_id(): Return MDL_ticket, if requested. dict_table_close(): Release MDL ticket, if requested. dict_fts_index_syncing(), dict_index_t::index_fts_syncing: Remove. row_drop_table_for_mysql() no longer needs to check these, because MDL guarantees that a fulltext index sync will not be in progress while MDL_EXCLUSIVE is protecting a DDL operation. dict_table_t::parse_name(): Parse the table name for acquiring MDL. purge_node_t::undo_recs: Change the type to std::list<trx_purge_rec_t*> (different container, and storing also roll_ptr). purge_node_t: Add mdl_ticket, last_table_id, purge_thd, mdl_hold_recs for acquiring MDL and for keeping the table open across multiple undo log records. purge_vcol_info_t, row_purge_store_vsec_cur(), row_purge_restore_vsec_cur(): Remove. We will acquire the MDL earlier. purge_sys_t::heap: Added, for reading undo log records. fts_sync_during_ddl(): Invoked during ALGORITHM=INPLACE operations to ensure that fts_sync_table() will not conflict with MDL_EXCLUSIVE. Uses fts_t::sync_message for bookkeeping.
2019-12-10 15:42:50 +02:00
trx_id_t trx_id);
/*****************************************************************//**
Constructs the version of a clustered index record which a consistent
read should see. We assume that the trx id stored in rec is such that
the consistent read should not see rec in its present version.
@return DB_SUCCESS or DB_MISSING_HISTORY */
dberr_t
row_vers_build_for_consistent_read(
/*===============================*/
const rec_t* rec, /*!< in: record in a clustered index; the
caller must have a latch on the page; this
latch locks the top of the stack of versions
of this records */
mtr_t* mtr, /*!< in: mtr holding the latch on rec; it will
also hold the latch on purge_view */
dict_index_t* index, /*!< in: the clustered index */
rec_offs** offsets,/*!< in/out: offsets returned by
rec_get_offsets(rec, index) */
ReadView* view, /*!< in: the consistent read view */
mem_heap_t** offset_heap,/*!< in/out: memory heap from which
the offsets are allocated */
mem_heap_t* in_heap,/*!< in: memory heap from which the memory for
*old_vers is allocated; memory for possible
intermediate versions is allocated and freed
locally within the function */
rec_t** old_vers,/*!< out, own: old version, or NULL
if the history is missing or the record
does not exist in the view, that is,
it was freshly inserted afterwards */
dtuple_t** vrow); /*!< out: reports virtual column info if any */
/*****************************************************************//**
Constructs the last committed version of a clustered index record,
which should be seen by a semi-consistent read. */
void
row_vers_build_for_semi_consistent_read(
/*====================================*/
MDEV-14638 - Replace trx_sys_t::rw_trx_set with LF_HASH trx_sys_t::rw_trx_set is implemented as std::set, which does a few quite expensive operations under trx_sys_t::mutex protection: e.g. malloc/free when adding/removing elements. Traversing b-tree is not that cheap either. This has negative scalability impact, which is especially visible when running oltp_update_index.lua benchmark on a ramdisk. To reduce trx_sys_t::mutex contention std::set is replaced with LF_HASH. None of LF_HASH operations require trx_sys_t::mutex (nor any other global mutex) protection. Another interesting issue observed with std::set is reproducible ~2% performance decline after benchmark is ran for ~60 seconds. With LF_HASH results are stable. All in all this patch optimises away one of three trx_sys->mutex locks per oltp_update_index.lua query. The other two critical sections became smaller. Relevant clean-ups: Replaced rw_trx_set iteration at startup with local set. The latter is needed because values inserted to rw_trx_list must be ordered by trx->id. Removed redundant conditions from trx_reference(): it is (and even was) never called with transactions that have trx->state == TRX_STATE_COMMITTED_IN_MEMORY. do_ref_count doesn't (and probably even didn't) make any sense: now it is called only when reference counter increment is actually requested. Moved condition out of mutex in trx_erase_lists(). trx_rw_is_active(), trx_rw_is_active_low() and trx_get_rw_trx_by_id() were greatly simplified and replaced by appropriate trx_rw_hash_t methods. Compared to rw_trx_set, rw_trx_hash holds transactions only in PREPARED or ACTIVE states. Transactions in COMMITTED state were required to be found at InnoDB startup only. They are now looked up in the local set. Removed unused trx_assert_recovered(). Removed unused innobase_get_trx() declaration. Removed rather semantically incorrect trx_sys_rw_trx_add(). Moved information printout from trx_sys_init_at_db_start() to trx_lists_init_at_db_start().
2017-12-13 15:40:41 +04:00
trx_t* caller_trx,/*!<in/out: trx of current thread */
const rec_t* rec, /*!< in: record in a clustered index; the
caller must have a latch on the page; this
latch locks the top of the stack of versions
of this records */
mtr_t* mtr, /*!< in: mtr holding the latch on rec */
dict_index_t* index, /*!< in: the clustered index */
rec_offs** offsets,/*!< in/out: offsets returned by
rec_get_offsets(rec, index) */
mem_heap_t** offset_heap,/*!< in/out: memory heap from which
the offsets are allocated */
mem_heap_t* in_heap,/*!< in: memory heap from which the memory for
*old_vers is allocated; memory for possible
intermediate versions is allocated and freed
locally within the function */
const rec_t** old_vers,/*!< out: rec, old version, or NULL if the
record does not exist in the view, that is,
it was freshly inserted afterwards */
dtuple_t** vrow); /*!< out: holds virtual column info if any
is updated in the view */
#endif