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mariadb/storage/innobase/include/trx0sys.h
Sergey Vojtovich 0ca2ea1a65 MDEV-14638 - Replace trx_sys_t::rw_trx_set with LF_HASH 
trx reference counter was updated under mutex and read without any
protection. This is both slow and unsafe. Use atomic operations for
reference counter accesses.
2018-01-11 12:30:53 +04:00

841 lines
26 KiB
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/*****************************************************************************
Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
Copyright (c) 2017, 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, Suite 500, Boston, MA 02110-1335 USA
*****************************************************************************/
/**************************************************//**
@file include/trx0sys.h
Transaction system
Created 3/26/1996 Heikki Tuuri
*******************************************************/
#ifndef trx0sys_h
#define trx0sys_h
#include "univ.i"
#include "buf0buf.h"
#include "fil0fil.h"
#include "trx0types.h"
#include "mem0mem.h"
#include "mtr0mtr.h"
#include "ut0byte.h"
#include "mem0mem.h"
#include "ut0lst.h"
#include "read0types.h"
#include "page0types.h"
#include "ut0mutex.h"
#include "trx0trx.h"
#ifdef WITH_WSREP
#include "trx0xa.h"
#endif /* WITH_WSREP */
typedef UT_LIST_BASE_NODE_T(trx_t) trx_ut_list_t;
// Forward declaration
class MVCC;
class ReadView;
/** The transaction system */
extern trx_sys_t* trx_sys;
/** Checks if a page address is the trx sys header page.
@param[in] page_id page id
@return true if trx sys header page */
UNIV_INLINE
bool
trx_sys_hdr_page(
const page_id_t& page_id);
/** Initialize the transaction system main-memory data structures. */
void trx_sys_init_at_db_start();
/*****************************************************************//**
Creates the trx_sys instance and initializes purge_queue and mutex. */
void
trx_sys_create(void);
/*================*/
/*****************************************************************//**
Creates and initializes the transaction system at the database creation. */
void
trx_sys_create_sys_pages(void);
/*==========================*/
/** @return an unallocated rollback segment slot in the TRX_SYS header
@retval ULINT_UNDEFINED if not found */
ulint
trx_sysf_rseg_find_free(mtr_t* mtr);
/**********************************************************************//**
Gets a pointer to the transaction system file copy and x-locks its page.
@return pointer to system file copy, page x-locked */
UNIV_INLINE
trx_sysf_t*
trx_sysf_get(
/*=========*/
mtr_t* mtr); /*!< in: mtr */
/*****************************************************************//**
Gets the space of the nth rollback segment slot in the trx system
file copy.
@return space id */
UNIV_INLINE
ulint
trx_sysf_rseg_get_space(
/*====================*/
trx_sysf_t* sys_header, /*!< in: trx sys file copy */
ulint i, /*!< in: slot index == rseg id */
mtr_t* mtr); /*!< in: mtr */
/*****************************************************************//**
Gets the page number of the nth rollback segment slot in the trx system
file copy.
@return page number, FIL_NULL if slot unused */
UNIV_INLINE
ulint
trx_sysf_rseg_get_page_no(
/*======================*/
trx_sysf_t* sys_header, /*!< in: trx sys file copy */
ulint i, /*!< in: slot index == rseg id */
mtr_t* mtr); /*!< in: mtr */
/*****************************************************************//**
Sets the space id of the nth rollback segment slot in the trx system
file copy. */
UNIV_INLINE
void
trx_sysf_rseg_set_space(
/*====================*/
trx_sysf_t* sys_header, /*!< in: trx sys file copy */
ulint i, /*!< in: slot index == rseg id */
ulint space, /*!< in: space id */
mtr_t* mtr); /*!< in: mtr */
/*****************************************************************//**
Sets the page number of the nth rollback segment slot in the trx system
file copy. */
UNIV_INLINE
void
trx_sysf_rseg_set_page_no(
/*======================*/
trx_sysf_t* sys_header, /*!< in: trx sys file copy */
ulint i, /*!< in: slot index == rseg id */
ulint page_no, /*!< in: page number, FIL_NULL if
the slot is reset to unused */
mtr_t* mtr); /*!< in: mtr */
/*****************************************************************//**
Allocates a new transaction id.
@return new, allocated trx id */
UNIV_INLINE
trx_id_t
trx_sys_get_new_trx_id();
/*===================*/
/*****************************************************************//**
Determines the maximum transaction id.
@return maximum currently allocated trx id; will be stale after the
next call to trx_sys_get_new_trx_id() */
UNIV_INLINE
trx_id_t
trx_sys_get_max_trx_id(void);
/*========================*/
#ifdef UNIV_DEBUG
/* Flag to control TRX_RSEG_N_SLOTS behavior debugging. */
extern uint trx_rseg_n_slots_debug;
#endif
/*****************************************************************//**
Writes a trx id to an index page. In case that the id size changes in
some future version, this function should be used instead of
mach_write_... */
UNIV_INLINE
void
trx_write_trx_id(
/*=============*/
byte* ptr, /*!< in: pointer to memory where written */
trx_id_t id); /*!< in: id */
/** Read a transaction identifier.
@return id */
inline
trx_id_t
trx_read_trx_id(const byte* ptr)
{
#if DATA_TRX_ID_LEN != 6
# error "DATA_TRX_ID_LEN != 6"
#endif
return(mach_read_from_6(ptr));
}
#ifdef UNIV_DEBUG
/** Check that the DB_TRX_ID in a record is valid.
@param[in] db_trx_id the DB_TRX_ID column to validate
@param[in] trx_id the id of the ALTER TABLE transaction */
inline bool trx_id_check(const void* db_trx_id, trx_id_t trx_id)
{
trx_id_t id = trx_read_trx_id(static_cast<const byte*>(db_trx_id));
ut_ad(id == 0 || id > trx_id);
return true;
}
#endif
/****************************************************************//**
Returns the minimum trx id in rw trx list. This is the smallest id for which
the trx can possibly be active. (But, you must look at the trx->state to
find out if the minimum trx id transaction itself is active, or already
committed.)
@return the minimum trx id, or trx_sys->max_trx_id if the trx list is empty */
UNIV_INLINE
trx_id_t
trx_rw_min_trx_id(void);
/*===================*/
/*****************************************************************//**
Updates the offset information about the end of the MySQL binlog entry
which corresponds to the transaction just being committed. In a MySQL
replication slave updates the latest master binlog position up to which
replication has proceeded. */
void
trx_sys_update_mysql_binlog_offset(
/*===============================*/
const char* file_name,/*!< in: MySQL log file name */
int64_t offset, /*!< in: position in that log file */
trx_sysf_t* sys_header, /*!< in: trx sys header */
mtr_t* mtr); /*!< in: mtr */
/** Display the MySQL binlog offset info if it is present in the trx
system header. */
void
trx_sys_print_mysql_binlog_offset();
#ifdef WITH_WSREP
/** Update WSREP XID info in sys_header of TRX_SYS_PAGE_NO = 5.
@param[in] xid Transaction XID
@param[in,out] sys_header sys_header
@param[in] mtr minitransaction */
UNIV_INTERN
void
trx_sys_update_wsrep_checkpoint(
const XID* xid,
trx_sysf_t* sys_header,
mtr_t* mtr);
/** Read WSREP checkpoint XID from sys header.
@param[out] xid WSREP XID
@return whether the checkpoint was present */
UNIV_INTERN
bool
trx_sys_read_wsrep_checkpoint(XID* xid);
#endif /* WITH_WSREP */
/*****************************************************************//**
Shutdown/Close the transaction system. */
void
trx_sys_close(void);
/*===============*/
/** Create the rollback segments.
@return whether the creation succeeded */
bool
trx_sys_create_rsegs();
/*****************************************************************//**
Get the number of transaction in the system, independent of their state.
@return count of transactions in trx_sys_t::trx_list */
UNIV_INLINE
ulint
trx_sys_get_n_rw_trx(void);
/*======================*/
/*********************************************************************
Check if there are any active (non-prepared) transactions.
@return total number of active transactions or 0 if none */
ulint
trx_sys_any_active_transactions(void);
/*=================================*/
#ifdef UNIV_DEBUG
/*************************************************************//**
Validate the trx_sys_t::rw_trx_list.
@return true if the list is valid */
bool
trx_sys_validate_trx_list();
/*========================*/
#endif /* UNIV_DEBUG */
/** The automatically created system rollback segment has this id */
#define TRX_SYS_SYSTEM_RSEG_ID 0
/** The offset of the transaction system header on the page */
#define TRX_SYS FSEG_PAGE_DATA
/** Transaction system header */
/*------------------------------------------------------------- @{ */
#define TRX_SYS_TRX_ID_STORE 0 /*!< the maximum trx id or trx
number modulo
TRX_SYS_TRX_ID_UPDATE_MARGIN
written to a file page by any
transaction; the assignment of
transaction ids continues from
this number rounded up by
TRX_SYS_TRX_ID_UPDATE_MARGIN
plus
TRX_SYS_TRX_ID_UPDATE_MARGIN
when the database is
started */
#define TRX_SYS_FSEG_HEADER 8 /*!< segment header for the
tablespace segment the trx
system is created into */
#define TRX_SYS_RSEGS (8 + FSEG_HEADER_SIZE)
/*!< the start of the array of
rollback segment specification
slots */
/*------------------------------------------------------------- @} */
/* Max number of rollback segments: the number of segment specification slots
in the transaction system array; rollback segment id must fit in one (signed)
byte, therefore 128; each slot is currently 8 bytes in size. If you want
to raise the level to 256 then you will need to fix some assertions that
impose the 7 bit restriction. e.g., mach_write_to_3() */
#define TRX_SYS_N_RSEGS 128
/** Maximum number of undo tablespaces (not counting the system tablespace) */
#define TRX_SYS_MAX_UNDO_SPACES (TRX_SYS_N_RSEGS - 1)
/** Maximum length of MySQL binlog file name, in bytes. */
#define TRX_SYS_MYSQL_LOG_NAME_LEN 512
/** Contents of TRX_SYS_MYSQL_LOG_MAGIC_N_FLD */
#define TRX_SYS_MYSQL_LOG_MAGIC_N 873422344
#if UNIV_PAGE_SIZE_MIN < 4096
# error "UNIV_PAGE_SIZE_MIN < 4096"
#endif
/** The offset of the MySQL binlog offset info in the trx system header */
#define TRX_SYS_MYSQL_LOG_INFO (UNIV_PAGE_SIZE - 1000)
#define TRX_SYS_MYSQL_LOG_MAGIC_N_FLD 0 /*!< magic number which is
TRX_SYS_MYSQL_LOG_MAGIC_N
if we have valid data in the
MySQL binlog info */
#define TRX_SYS_MYSQL_LOG_OFFSET 4 /*!< the 64-bit offset
within that file */
#define TRX_SYS_MYSQL_LOG_NAME 12 /*!< MySQL log file name */
/** Memory map TRX_SYS_PAGE_NO = 5 when UNIV_PAGE_SIZE = 4096
0...37 FIL_HEADER
38...45 TRX_SYS_TRX_ID_STORE
46...55 TRX_SYS_FSEG_HEADER (FSEG_HEADER_SIZE == 10)
56 TRX_SYS_RSEGS
56...59 TRX_SYS_RSEG_SPACE for slot 0
60...63 TRX_SYS_RSEG_PAGE_NO for slot 0
64...67 TRX_SYS_RSEG_SPACE for slot 1
68...71 TRX_SYS_RSEG_PAGE_NO for slot 1
....
594..597 TRX_SYS_RSEG_SPACE for slot 72
598..601 TRX_SYS_RSEG_PAGE_NO for slot 72
...
...1063 TRX_SYS_RSEG_PAGE_NO for slot 126
(UNIV_PAGE_SIZE-3500 WSREP ::: FAIL would overwrite undo tablespace
space_id, page_no pairs :::)
596 TRX_SYS_WSREP_XID_INFO TRX_SYS_WSREP_XID_MAGIC_N_FLD
600 TRX_SYS_WSREP_XID_FORMAT
604 TRX_SYS_WSREP_XID_GTRID_LEN
608 TRX_SYS_WSREP_XID_BQUAL_LEN
612 TRX_SYS_WSREP_XID_DATA (len = 128)
739 TRX_SYS_WSREP_XID_DATA_END
FIXED WSREP XID info offsets for 4k page size 10.0.32-galera
(UNIV_PAGE_SIZE-2500)
1596 TRX_SYS_WSREP_XID_INFO TRX_SYS_WSREP_XID_MAGIC_N_FLD
1600 TRX_SYS_WSREP_XID_FORMAT
1604 TRX_SYS_WSREP_XID_GTRID_LEN
1608 TRX_SYS_WSREP_XID_BQUAL_LEN
1612 TRX_SYS_WSREP_XID_DATA (len = 128)
1739 TRX_SYS_WSREP_XID_DATA_END
(UNIV_PAGE_SIZE - 2000 MYSQL MASTER LOG)
2096 TRX_SYS_MYSQL_MASTER_LOG_INFO TRX_SYS_MYSQL_LOG_MAGIC_N_FLD
2100 TRX_SYS_MYSQL_LOG_OFFSET_HIGH
2104 TRX_SYS_MYSQL_LOG_OFFSET_LOW
2108 TRX_SYS_MYSQL_LOG_NAME
(UNIV_PAGE_SIZE - 1000 MYSQL LOG)
3096 TRX_SYS_MYSQL_LOG_INFO TRX_SYS_MYSQL_LOG_MAGIC_N_FLD
3100 TRX_SYS_MYSQL_LOG_OFFSET_HIGH
3104 TRX_SYS_MYSQL_LOG_OFFSET_LOW
3108 TRX_SYS_MYSQL_LOG_NAME
(UNIV_PAGE_SIZE - 200 DOUBLEWRITE)
3896 TRX_SYS_DOUBLEWRITE TRX_SYS_DOUBLEWRITE_FSEG
3906 TRX_SYS_DOUBLEWRITE_MAGIC
3910 TRX_SYS_DOUBLEWRITE_BLOCK1
3914 TRX_SYS_DOUBLEWRITE_BLOCK2
3918 TRX_SYS_DOUBLEWRITE_REPEAT
3930 TRX_SYS_DOUBLEWRITE_SPACE_ID_STORED_N
(UNIV_PAGE_SIZE - 8, TAILER)
4088..4096 FIL_TAILER
*/
#ifdef WITH_WSREP
/** The offset to WSREP XID headers */
#define TRX_SYS_WSREP_XID_INFO std::max(srv_page_size - 3500, 1596UL)
#define TRX_SYS_WSREP_XID_MAGIC_N_FLD 0
#define TRX_SYS_WSREP_XID_MAGIC_N 0x77737265
/** XID field: formatID, gtrid_len, bqual_len, xid_data */
#define TRX_SYS_WSREP_XID_LEN (4 + 4 + 4 + XIDDATASIZE)
#define TRX_SYS_WSREP_XID_FORMAT 4
#define TRX_SYS_WSREP_XID_GTRID_LEN 8
#define TRX_SYS_WSREP_XID_BQUAL_LEN 12
#define TRX_SYS_WSREP_XID_DATA 16
#endif /* WITH_WSREP*/
/** Doublewrite buffer */
/* @{ */
/** The offset of the doublewrite buffer header on the trx system header page */
#define TRX_SYS_DOUBLEWRITE (UNIV_PAGE_SIZE - 200)
/*-------------------------------------------------------------*/
#define TRX_SYS_DOUBLEWRITE_FSEG 0 /*!< fseg header of the fseg
containing the doublewrite
buffer */
#define TRX_SYS_DOUBLEWRITE_MAGIC FSEG_HEADER_SIZE
/*!< 4-byte magic number which
shows if we already have
created the doublewrite
buffer */
#define TRX_SYS_DOUBLEWRITE_BLOCK1 (4 + FSEG_HEADER_SIZE)
/*!< page number of the
first page in the first
sequence of 64
(= FSP_EXTENT_SIZE) consecutive
pages in the doublewrite
buffer */
#define TRX_SYS_DOUBLEWRITE_BLOCK2 (8 + FSEG_HEADER_SIZE)
/*!< page number of the
first page in the second
sequence of 64 consecutive
pages in the doublewrite
buffer */
#define TRX_SYS_DOUBLEWRITE_REPEAT 12 /*!< we repeat
TRX_SYS_DOUBLEWRITE_MAGIC,
TRX_SYS_DOUBLEWRITE_BLOCK1,
TRX_SYS_DOUBLEWRITE_BLOCK2
so that if the trx sys
header is half-written
to disk, we still may
be able to recover the
information */
/** If this is not yet set to TRX_SYS_DOUBLEWRITE_SPACE_ID_STORED_N,
we must reset the doublewrite buffer, because starting from 4.1.x the
space id of a data page is stored into
FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID. */
#define TRX_SYS_DOUBLEWRITE_SPACE_ID_STORED (24 + FSEG_HEADER_SIZE)
/*-------------------------------------------------------------*/
/** Contents of TRX_SYS_DOUBLEWRITE_MAGIC */
#define TRX_SYS_DOUBLEWRITE_MAGIC_N 536853855
/** Contents of TRX_SYS_DOUBLEWRITE_SPACE_ID_STORED */
#define TRX_SYS_DOUBLEWRITE_SPACE_ID_STORED_N 1783657386
/** Size of the doublewrite block in pages */
#define TRX_SYS_DOUBLEWRITE_BLOCK_SIZE FSP_EXTENT_SIZE
/* @} */
trx_t* current_trx();
struct rw_trx_hash_element_t
{
rw_trx_hash_element_t(): trx(0)
{
mutex_create(LATCH_ID_RW_TRX_HASH_ELEMENT, &mutex);
}
~rw_trx_hash_element_t()
{
mutex_free(&mutex);
}
trx_id_t id; /* lf_hash_init() relies on this to be first in the struct */
trx_t *trx;
ib_mutex_t mutex;
};
/**
Wrapper around LF_HASH to store set of in memory read-write transactions.
*/
class rw_trx_hash_t
{
LF_HASH hash;
/**
Constructor callback for lock-free allocator.
Object is just allocated and is not yet accessible via rw_trx_hash by
concurrent threads. Object can be reused multiple times before it is freed.
Every time object is being reused initializer() callback is called.
*/
static void rw_trx_hash_constructor(uchar *arg)
{
new(arg + LF_HASH_OVERHEAD) rw_trx_hash_element_t();
}
/**
Destructor callback for lock-free allocator.
Object is about to be freed and is not accessible via rw_trx_hash by
concurrent threads.
*/
static void rw_trx_hash_destructor(uchar *arg)
{
reinterpret_cast<rw_trx_hash_element_t*>
(arg + LF_HASH_OVERHEAD)->~rw_trx_hash_element_t();
}
/**
Initializer callback for lock-free hash.
Object is not yet accessible via rw_trx_hash by concurrent threads, but is
about to become such. Object id can be changed only by this callback and
remains the same until all pins to this object are released.
Object trx can be changed to 0 by erase() under object mutex protection,
which indicates it is about to be removed from lock-free hash and become
not accessible by concurrent threads.
*/
static void rw_trx_hash_initializer(LF_HASH *,
rw_trx_hash_element_t *element,
trx_t *trx)
{
element->trx= trx;
element->id= trx->id;
trx->rw_trx_hash_element= element;
}
/**
Gets LF_HASH pins.
Pins are used to protect object from being destroyed or reused. They are
normally stored in trx object for quick access. If caller doesn't have trx
available, we try to get it using currnet_trx(). If caller doesn't have trx
at all, temporary pins are allocated.
*/
LF_PINS *get_pins(trx_t *trx)
{
if (!trx->rw_trx_hash_pins)
{
trx->rw_trx_hash_pins= lf_hash_get_pins(&hash);
ut_a(trx->rw_trx_hash_pins);
}
return trx->rw_trx_hash_pins;
}
public:
void init()
{
lf_hash_init(&hash, sizeof(rw_trx_hash_element_t), LF_HASH_UNIQUE, 0,
sizeof(trx_id_t), 0, &my_charset_bin);
hash.alloc.constructor= rw_trx_hash_constructor;
hash.alloc.destructor= rw_trx_hash_destructor;
hash.initializer=
reinterpret_cast<lf_hash_initializer>(rw_trx_hash_initializer);
}
void destroy()
{
lf_hash_destroy(&hash);
}
/**
Releases LF_HASH pins.
Must be called by thread that owns trx_t object when the latter is being
"detached" from thread (e.g. released to the pool by trx_free()). Can be
called earlier if thread is expected not to use rw_trx_hash.
Since pins are not allowed to be transferred to another thread,
initialisation thread calls this for recovered transactions.
*/
void put_pins(trx_t *trx)
{
if (trx->rw_trx_hash_pins)
{
lf_hash_put_pins(trx->rw_trx_hash_pins);
trx->rw_trx_hash_pins= 0;
}
}
/**
Finds trx object in lock-free hash with given id.
Only ACTIVE or PREPARED trx objects may participate in hash. Nevertheless
the transaction may get committed before this method returns.
With do_ref_count == false the caller may dereference returned trx pointer
only if lock_sys->mutex was acquired before calling find().
With do_ref_count == true caller may dereference trx even if it is not
holding lock_sys->mutex. Caller is responsible for calling
trx->release_reference() when it is done playing with trx.
Ideally this method should get caller rw_trx_hash_pins along with trx
object as a parameter, similar to insert() and erase(). However most
callers lose trx early in their call chains and it is not that easy to pass
them through.
So we take more expensive approach: get trx through current_thd()->ha_data.
Some threads don't have trx attached to THD, and at least server
initialisation thread, fts_optimize_thread, srv_master_thread,
dict_stats_thread, srv_monitor_thread, btr_defragment_thread don't even
have THD at all. For such cases we allocate pins only for duration of
search and free them immediately.
This has negative performance impact and should be fixed eventually (by
passing caller_trx as a parameter). Still stream of DML is more or less Ok.
@return
@retval 0 not found
@retval pointer to trx
*/
trx_t *find(trx_t *caller_trx, trx_id_t trx_id, bool do_ref_count= false)
{
/*
In MariaDB 10.3, purge will reset DB_TRX_ID to 0
when the history is lost. Read/write transactions will
always have a nonzero trx_t::id; there the value 0 is
reserved for transactions that did not write or lock
anything yet.
*/
if (!trx_id)
return NULL;
trx_t *trx= 0;
LF_PINS *pins= caller_trx ? get_pins(caller_trx) : lf_hash_get_pins(&hash);
ut_a(pins);
rw_trx_hash_element_t *element= reinterpret_cast<rw_trx_hash_element_t*>
(lf_hash_search(&hash, pins, reinterpret_cast<const void*>(&trx_id),
sizeof(trx_id_t)));
if (element)
{
mutex_enter(&element->mutex);
lf_hash_search_unpin(pins);
if ((trx= element->trx))
{
if (do_ref_count)
trx->reference();
#ifdef UNIV_DEBUG
mutex_enter(&trx->mutex);
ut_ad(trx_state_eq(trx, TRX_STATE_ACTIVE) ||
trx_state_eq(trx, TRX_STATE_PREPARED));
mutex_exit(&trx->mutex);
#endif
}
mutex_exit(&element->mutex);
}
if (!caller_trx)
lf_hash_put_pins(pins);
return trx;
}
trx_t *find(trx_id_t trx_id, bool do_ref_count= false)
{
return find(current_trx(), trx_id, do_ref_count);
}
/**
Inserts trx to lock-free hash.
Object becomes accessible via rw_trx_hash.
*/
void insert(trx_t *trx)
{
ut_ad(trx_state_eq(trx, TRX_STATE_ACTIVE) ||
trx_state_eq(trx, TRX_STATE_PREPARED));
int res= lf_hash_insert(&hash, get_pins(trx),
reinterpret_cast<void*>(trx));
ut_a(res == 0);
}
/**
Removes trx from lock-free hash.
Object becomes not accessible via rw_trx_hash. But it still can be pinned
by concurrent find(), which is supposed to release it immediately after
it sees object trx is 0.
*/
void erase(trx_t *trx)
{
ut_ad(trx_state_eq(trx, TRX_STATE_ACTIVE) ||
trx_state_eq(trx, TRX_STATE_PREPARED));
mutex_enter(&trx->rw_trx_hash_element->mutex);
trx->rw_trx_hash_element->trx= 0;
mutex_exit(&trx->rw_trx_hash_element->mutex);
int res= lf_hash_delete(&hash, get_pins(trx),
reinterpret_cast<const void*>(&trx->id),
sizeof(trx_id_t));
ut_a(res == 0);
}
/**
Returns the number of elements in the hash.
The number is exact only if hash is protected against concurrent
modifications (e.g. single threaded startup or hash is protected
by some mutex). Otherwise the number may be used as a hint only,
because it may change even before this method returns.
*/
int32_t size()
{
return my_atomic_load32_explicit(&hash.count, MY_MEMORY_ORDER_RELAXED);
}
};
/** The transaction system central memory data structure. */
struct trx_sys_t {
TrxSysMutex mutex; /*!< mutex protecting most fields in
this structure except when noted
otherwise */
MVCC* mvcc; /*!< Multi version concurrency control
manager */
volatile trx_id_t
max_trx_id; /*!< The smallest number not yet
assigned as a transaction id or
transaction number. This is declared
volatile because it can be accessed
without holding any mutex during
AC-NL-RO view creation. */
trx_ut_list_t serialisation_list;
/*!< Ordered on trx_t::no of all the
currenrtly active RW transactions */
#ifdef UNIV_DEBUG
trx_id_t rw_max_trx_id; /*!< Max trx id of read-write
transactions which exist or existed */
#endif /* UNIV_DEBUG */
/** Avoid false sharing */
const char pad1[CACHE_LINE_SIZE];
trx_ut_list_t rw_trx_list; /*!< List of active and committed in
memory read-write transactions, sorted
on trx id, biggest first. Recovered
transactions are always on this list. */
/** Avoid false sharing */
const char pad2[CACHE_LINE_SIZE];
trx_ut_list_t mysql_trx_list; /*!< List of transactions created
for MySQL. All user transactions are
on mysql_trx_list. The rw_trx_list
can contain system transactions and
recovered transactions that will not
be in the mysql_trx_list.
mysql_trx_list may additionally contain
transactions that have not yet been
started in InnoDB. */
trx_ids_t rw_trx_ids; /*!< Array of Read write transaction IDs
for MVCC snapshot. A ReadView would take
a snapshot of these transactions whose
changes are not visible to it. We should
remove transactions from the list before
committing in memory and releasing locks
to ensure right order of removal and
consistent snapshot. */
/** Avoid false sharing */
const char pad3[CACHE_LINE_SIZE];
/** Temporary rollback segments */
trx_rseg_t* temp_rsegs[TRX_SYS_N_RSEGS];
/** Avoid false sharing */
const char pad4[CACHE_LINE_SIZE];
trx_rseg_t* rseg_array[TRX_SYS_N_RSEGS];
/*!< Pointer array to rollback
segments; NULL if slot not in use;
created and destroyed in
single-threaded mode; not protected
by any mutex, because it is read-only
during multi-threaded operation */
ulint rseg_history_len;
/*!< Length of the TRX_RSEG_HISTORY
list (update undo logs for committed
transactions), protected by
rseg->mutex */
const char rw_trx_hash_pre_pad[CACHE_LINE_SIZE];
/**
Lock-free hash of in memory read-write transactions.
Works faster when it is on it's own cache line (tested).
*/
rw_trx_hash_t rw_trx_hash;
const char rw_trx_hash_post_pad[CACHE_LINE_SIZE];
ulint n_prepared_trx; /*!< Number of transactions currently
in the XA PREPARED state */
ulint n_prepared_recovered_trx; /*!< Number of transactions
currently in XA PREPARED state that are
also recovered. Such transactions cannot
be added during runtime. They can only
occur after recovery if mysqld crashed
while there were XA PREPARED
transactions. We disable query cache
if such transactions exist. */
};
/** When a trx id which is zero modulo this number (which must be a power of
two) is assigned, the field TRX_SYS_TRX_ID_STORE on the transaction system
page is updated */
#define TRX_SYS_TRX_ID_WRITE_MARGIN ((trx_id_t) 256)
/** Test if trx_sys->mutex is owned. */
#define trx_sys_mutex_own() (trx_sys->mutex.is_owned())
/** Acquire the trx_sys->mutex. */
#define trx_sys_mutex_enter() do { \
mutex_enter(&trx_sys->mutex); \
} while (0)
/** Release the trx_sys->mutex. */
#define trx_sys_mutex_exit() do { \
trx_sys->mutex.exit(); \
} while (0)
#include "trx0sys.ic"
#endif
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