mariadb/include/trx0trx.h

/*****************************************************************************

Copyright (c) 1996, 2010, Innobase Oy. All Rights Reserved.

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 St, Fifth Floor, Boston, MA 02110-1301 USA

*****************************************************************************/

/**************************************************//**
@file include/trx0trx.h
The transaction

Created 3/26/1996 Heikki Tuuri
*******************************************************/

#ifndef trx0trx_h
#define trx0trx_h

#include "univ.i"
#include "trx0types.h"
#include "dict0types.h"
#ifndef UNIV_HOTBACKUP
#include "lock0types.h"
#include "usr0types.h"
#include "que0types.h"
#include "mem0mem.h"
#include "read0types.h"
#include "trx0xa.h"
#include "ut0vec.h"

/** Dummy session used currently in MySQL interface */
extern sess_t*	trx_dummy_sess;

/** Number of transactions currently allocated for MySQL: protected by
the kernel mutex */
extern ulint	trx_n_mysql_transactions;
/** Number of transactions currently in the XA PREPARED state: protected by
the kernel mutex */
extern ulint	trx_n_prepared;

/********************************************************************//**
In XtraDB it is impossible for a transaction to own a search latch outside of
InnoDB code, so there is nothing to release on demand.  We keep this function to
simplify maintenance.*/
UNIV_INLINE
void
trx_search_latch_release_if_reserved(
/*=================================*/
	trx_t*	   trx __attribute__((unused))); /*!< in: transaction */
/******************************************************************//**
Set detailed error message for the transaction. */
UNIV_INTERN
void
trx_set_detailed_error(
/*===================*/
	trx_t*		trx,	/*!< in: transaction struct */
	const char*	msg);	/*!< in: detailed error message */
/*************************************************************//**
Set detailed error message for the transaction from a file. Note that the
file is rewinded before reading from it. */
UNIV_INTERN
void
trx_set_detailed_error_from_file(
/*=============================*/
	trx_t*	trx,	/*!< in: transaction struct */
	FILE*	file);	/*!< in: file to read message from */
/****************************************************************//**
Retrieves the error_info field from a trx.
@return	the error info */
UNIV_INLINE
const dict_index_t*
trx_get_error_info(
/*===============*/
	const trx_t*	trx);	/*!< in: trx object */
/****************************************************************//**
Creates and initializes a transaction object.
@return	own: the transaction */
UNIV_INTERN
trx_t*
trx_create(
/*=======*/
	sess_t*	sess)	/*!< in: session */
	__attribute__((nonnull));
/********************************************************************//**
Creates a transaction object for MySQL.
@return	own: transaction object */
UNIV_INTERN
trx_t*
trx_allocate_for_mysql(void);
/*========================*/
/********************************************************************//**
Creates a transaction object for background operations by the master thread.
@return	own: transaction object */
UNIV_INTERN
trx_t*
trx_allocate_for_background(void);
/*=============================*/
/********************************************************************//**
Frees a transaction object. */
UNIV_INTERN
void
trx_free(
/*=====*/
	trx_t*	trx);	/*!< in, own: trx object */
/********************************************************************//**
At shutdown, frees a transaction object that is in the PREPARED state. */
UNIV_INTERN
void
trx_free_prepared(
/*==============*/
	trx_t*	trx)	/*!< in, own: trx object */
	UNIV_COLD __attribute__((nonnull));
/********************************************************************//**
Frees a transaction object for MySQL. */
UNIV_INTERN
void
trx_free_for_mysql(
/*===============*/
	trx_t*	trx);	/*!< in, own: trx object */
/********************************************************************//**
Frees a transaction object of a background operation of the master thread. */
UNIV_INTERN
void
trx_free_for_background(
/*====================*/
	trx_t*	trx);	/*!< in, own: trx object */
/****************************************************************//**
Creates trx objects for transactions and initializes the trx list of
trx_sys at database start. Rollback segment and undo log lists must
already exist when this function is called, because the lists of
transactions to be rolled back or cleaned up are built based on the
undo log lists. */
UNIV_INTERN
void
trx_lists_init_at_db_start(void);
/*============================*/
/****************************************************************//**
Starts a new transaction.
@return TRUE if success, FALSE if the rollback segment could not
support this many transactions */
UNIV_INTERN
ibool
trx_start(
/*======*/
	trx_t*	trx,	/*!< in: transaction */
	ulint	rseg_id);/*!< in: rollback segment id; if ULINT_UNDEFINED
			is passed, the system chooses the rollback segment
			automatically in a round-robin fashion */
/****************************************************************//**
Starts a new transaction.
@return	TRUE */
UNIV_INTERN
ibool
trx_start_low(
/*==========*/
	trx_t*	trx,	/*!< in: transaction */
	ulint	rseg_id);/*!< in: rollback segment id; if ULINT_UNDEFINED
			is passed, the system chooses the rollback segment
			automatically in a round-robin fashion */
/*************************************************************//**
Starts the transaction if it is not yet started. */
UNIV_INLINE
void
trx_start_if_not_started(
/*=====================*/
	trx_t*	trx);	/*!< in: transaction */
/*************************************************************//**
Starts the transaction if it is not yet started. Assumes we have reserved
the kernel mutex! */
UNIV_INLINE
void
trx_start_if_not_started_low(
/*=========================*/
	trx_t*	trx);	/*!< in: transaction */
/****************************************************************//**
Commits a transaction. */
UNIV_INTERN
void
trx_commit_off_kernel(
/*==================*/
	trx_t*	trx);	/*!< in: transaction */
/****************************************************************//**
Cleans up a transaction at database startup. The cleanup is needed if
the transaction already got to the middle of a commit when the database
crashed, and we cannot roll it back. */
UNIV_INTERN
void
trx_cleanup_at_db_startup(
/*======================*/
	trx_t*	trx);	/*!< in: transaction */
/**********************************************************************//**
Does the transaction commit for MySQL.
@return	DB_SUCCESS or error number */
UNIV_INTERN
ulint
trx_commit_for_mysql(
/*=================*/
	trx_t*	trx);	/*!< in: trx handle */
/**********************************************************************//**
Does the transaction prepare for MySQL.
@return	0 or error number */
UNIV_INTERN
ulint
trx_prepare_for_mysql(
/*==================*/
	trx_t*	trx);	/*!< in: trx handle */
/**********************************************************************//**
This function is used to find number of prepared transactions and
their transaction objects for a recovery.
@return	number of prepared transactions */
UNIV_INTERN
int
trx_recover_for_mysql(
/*==================*/
	XID*	xid_list,	/*!< in/out: prepared transactions */
	ulint	len);		/*!< in: number of slots in xid_list */
/*******************************************************************//**
This function is used to find one X/Open XA distributed transaction
which is in the prepared state
@return	trx or NULL; on match, the trx->xid will be invalidated */
UNIV_INTERN
trx_t *
trx_get_trx_by_xid(
/*===============*/
	const XID*	xid);	/*!< in: X/Open XA transaction identifier */
/**********************************************************************//**
If required, flushes the log to disk if we called trx_commit_for_mysql()
with trx->flush_log_later == TRUE.
@return	0 or error number */
UNIV_INTERN
ulint
trx_commit_complete_for_mysql(
/*==========================*/
	trx_t*	trx);	/*!< in: trx handle */
/**********************************************************************//**
Marks the latest SQL statement ended. */
UNIV_INTERN
void
trx_mark_sql_stat_end(
/*==================*/
	trx_t*	trx);	/*!< in: trx handle */
/********************************************************************//**
Assigns a read view for a consistent read query. All the consistent reads
within the same transaction will get the same read view, which is created
when this function is first called for a new started transaction.
@return	consistent read view */
UNIV_INTERN
read_view_t*
trx_assign_read_view(
/*=================*/
	trx_t*	trx);	/*!< in: active transaction */
/***********************************************************//**
The transaction must be in the TRX_QUE_LOCK_WAIT state. Puts it to
the TRX_QUE_RUNNING state and releases query threads which were
waiting for a lock in the wait_thrs list. */
UNIV_INTERN
void
trx_end_lock_wait(
/*==============*/
	trx_t*	trx);	/*!< in: transaction */
/****************************************************************//**
Sends a signal to a trx object. */
UNIV_INTERN
void
trx_sig_send(
/*=========*/
	trx_t*		trx,		/*!< in: trx handle */
	ulint		type,		/*!< in: signal type */
	ulint		sender,		/*!< in: TRX_SIG_SELF or
					TRX_SIG_OTHER_SESS */
	que_thr_t*	receiver_thr,	/*!< in: query thread which wants the
					reply, or NULL; if type is
					TRX_SIG_END_WAIT, this must be NULL */
	trx_savept_t*	savept,		/*!< in: possible rollback savepoint, or
					NULL */
	que_thr_t**	next_thr);	/*!< in/out: next query thread to run;
					if the value which is passed in is
					a pointer to a NULL pointer, then the
					calling function can start running
					a new query thread; if the parameter
					is NULL, it is ignored */
/****************************************************************//**
Send the reply message when a signal in the queue of the trx has
been handled. */
UNIV_INTERN
void
trx_sig_reply(
/*==========*/
	trx_sig_t*	sig,		/*!< in: signal */
	que_thr_t**	next_thr);	/*!< in/out: next query thread to run;
					if the value which is passed in is
					a pointer to a NULL pointer, then the
					calling function can start running
					a new query thread */
/****************************************************************//**
Removes the signal object from a trx signal queue. */
UNIV_INTERN
void
trx_sig_remove(
/*===========*/
	trx_t*		trx,	/*!< in: trx handle */
	trx_sig_t*	sig);	/*!< in, own: signal */
/****************************************************************//**
Starts handling of a trx signal. */
UNIV_INTERN
void
trx_sig_start_handle(
/*=================*/
	trx_t*		trx,		/*!< in: trx handle */
	que_thr_t**	next_thr);	/*!< in/out: next query thread to run;
					if the value which is passed in is
					a pointer to a NULL pointer, then the
					calling function can start running
					a new query thread */
/****************************************************************//**
Ends signal handling. If the session is in the error state, and
trx->graph_before_signal_handling != NULL, returns control to the error
handling routine of the graph (currently only returns the control to the
graph root which then sends an error message to the client). */
UNIV_INTERN
void
trx_end_signal_handling(
/*====================*/
	trx_t*	trx);	/*!< in: trx */
/*********************************************************************//**
Creates a commit command node struct.
@return	own: commit node struct */
UNIV_INTERN
commit_node_t*
commit_node_create(
/*===============*/
	mem_heap_t*	heap);	/*!< in: mem heap where created */
/***********************************************************//**
Performs an execution step for a commit type node in a query graph.
@return	query thread to run next, or NULL */
UNIV_INTERN
que_thr_t*
trx_commit_step(
/*============*/
	que_thr_t*	thr);	/*!< in: query thread */

/**********************************************************************//**
Prints info about a transaction to the given file. The caller must own the
kernel mutex. */
UNIV_INTERN
void
trx_print(
/*======*/
	FILE*	f,		/*!< in: output stream */
	trx_t*	trx,		/*!< in: transaction */
	ulint	max_query_len);	/*!< in: max query length to print, or 0 to
				   use the default max length */

/** Type of data dictionary operation */
typedef enum trx_dict_op {
	/** The transaction is not modifying the data dictionary. */
	TRX_DICT_OP_NONE = 0,
	/** The transaction is creating a table or an index, or
	dropping a table.  The table must be dropped in crash
	recovery.  This and TRX_DICT_OP_NONE are the only possible
	operation modes in crash recovery. */
	TRX_DICT_OP_TABLE = 1,
	/** The transaction is creating or dropping an index in an
	existing table.  In crash recovery, the data dictionary
	must be locked, but the table must not be dropped. */
	TRX_DICT_OP_INDEX = 2
} trx_dict_op_t;

/**********************************************************************//**
Determine if a transaction is a dictionary operation.
@return	dictionary operation mode */
UNIV_INLINE
enum trx_dict_op
trx_get_dict_operation(
/*===================*/
	const trx_t*	trx)	/*!< in: transaction */
	__attribute__((pure));
/**********************************************************************//**
Flag a transaction a dictionary operation. */
UNIV_INLINE
void
trx_set_dict_operation(
/*===================*/
	trx_t*			trx,	/*!< in/out: transaction */
	enum trx_dict_op	op);	/*!< in: operation, not
					TRX_DICT_OP_NONE */

#ifndef UNIV_HOTBACKUP
/**********************************************************************//**
Determines if the currently running transaction has been interrupted.
@return	TRUE if interrupted */
UNIV_INTERN
ibool
trx_is_interrupted(
/*===============*/
	trx_t*	trx);	/*!< in: transaction */
/**********************************************************************//**
Determines if the currently running transaction is in strict mode.
@return	TRUE if strict */
UNIV_INTERN
ibool
trx_is_strict(
/*==========*/
	trx_t*	trx);	/*!< in: transaction */
#else /* !UNIV_HOTBACKUP */
#define trx_is_interrupted(trx) FALSE
#endif /* !UNIV_HOTBACKUP */

/*******************************************************************//**
Calculates the "weight" of a transaction. The weight of one transaction
is estimated as the number of altered rows + the number of locked rows.
@param t	transaction
@return		transaction weight */
#define TRX_WEIGHT(t)	((t)->undo_no + UT_LIST_GET_LEN((t)->trx_locks))

/*******************************************************************//**
Compares the "weight" (or size) of two transactions. Transactions that
have edited non-transactional tables are considered heavier than ones
that have not.
@return	TRUE if weight(a) >= weight(b) */
UNIV_INTERN
ibool
trx_weight_ge(
/*==========*/
	const trx_t*	a,	/*!< in: the first transaction to be compared */
	const trx_t*	b);	/*!< in: the second transaction to be compared */

/* Maximum length of a string that can be returned by
trx_get_que_state_str(). */
#define TRX_QUE_STATE_STR_MAX_LEN	12 /* "ROLLING BACK" */

/*******************************************************************//**
Retrieves transaction's que state in a human readable string. The string
should not be free()'d or modified.
@return	string in the data segment */
UNIV_INLINE
const char*
trx_get_que_state_str(
/*==================*/
	const trx_t*	trx);	/*!< in: transaction */

/*************************************************************//**
Callback function for trx_find_descriptor() to compare trx IDs. */
UNIV_INTERN
int
trx_descr_cmp(
/*==========*/
	const void *a,	/*!< in: pointer to first comparison argument */
	const void *b);	/*!< in: pointer to second comparison argument */

/*************************************************************//**
Release a slot for a given trx in the global descriptors array. */
UNIV_INTERN
void
trx_release_descriptor(
/*===================*/
	trx_t* trx);	/*!< in: trx pointer */

/* Signal to a transaction */
struct trx_sig_struct{
	unsigned	type:3;		/*!< signal type */
	unsigned	sender:1;	/*!< TRX_SIG_SELF or
					TRX_SIG_OTHER_SESS */
	que_thr_t*	receiver;	/*!< non-NULL if the sender of the signal
					wants reply after the operation induced
					by the signal is completed */
	trx_savept_t	savept;		/*!< possible rollback savepoint */
	UT_LIST_NODE_T(trx_sig_t)
			signals;	/*!< queue of pending signals to the
					transaction */
	UT_LIST_NODE_T(trx_sig_t)
			reply_signals;	/*!< list of signals for which the sender
					transaction is waiting a reply */
};

#define TRX_MAGIC_N	91118598

/* The transaction handle; every session has a trx object which is freed only
when the session is freed; in addition there may be session-less transactions
rolling back after a database recovery */

struct trx_struct{
	ulint		magic_n;

	/* These fields are not protected by any mutex. */
	const char*	op_info;	/*!< English text describing the
					current operation, or an empty
					string */
	ulint		state;		/*!< state of the trx from the point of
					view of concurrency control: TRX_ACTIVE,
					TRX_COMMITTED_IN_MEMORY, ...  This was
					called 'conc_state' in the upstream and
					has been renamed in Percona Server,
					because changing it's value to/from
					either TRX_ACTIVE or TRX_PREPARED
					requires calling
					trx_reserve_descriptor() /
					trx_release_descriptor(). Different name
					ensures we notice any new code changing
					the state. */
	/*------------------------------*/
	/* MySQL has a transaction coordinator to coordinate two phase
       	commit between multiple storage engines and the binary log. When
       	an engine participates in a transaction, it's responsible for
       	registering itself using the trans_register_ha() API. */
	unsigned	is_registered:1;/* This flag is set to 1 after the
				       	transaction has been registered with
				       	the coordinator using the XA API, and
				       	is set to 0 after commit or rollback. */
	unsigned	owns_prepare_mutex:1;/* 1 if owns prepare mutex, if
					this is set to 1 then registered should
					also be set to 1. This is used in the
					XA code */
	unsigned	called_commit_ordered:1;/* 1 if innobase_commit_ordered has run. */
	unsigned	is_in_trx_serial_list:1;
					/* Set when transaction is in the
					trx_serial_list */
	/*------------------------------*/
	ulint		isolation_level;/* TRX_ISO_REPEATABLE_READ, ... */
	ulint		check_foreigns;	/* normally TRUE, but if the user
					wants to suppress foreign key checks,
					(in table imports, for example) we
					set this FALSE */
	ulint		check_unique_secondary;
					/* normally TRUE, but if the user
					wants to speed up inserts by
					suppressing unique key checks
					for secondary indexes when we decide
					if we can use the insert buffer for
					them, we set this FALSE */
	ulint		support_xa;	/*!< normally we do the XA two-phase
					commit steps, but by setting this to
					FALSE, one can save CPU time and about
					150 bytes in the undo log size as then
					we skip XA steps */
	ulint		fake_changes;
	ulint		flush_log_later;/* In 2PC, we hold the
					prepare_commit mutex across
					both phases. In that case, we
					defer flush of the logs to disk
					until after we release the
					mutex. */
	ulint		must_flush_log_later;/* this flag is set to TRUE in
					trx_commit_off_kernel() if
					flush_log_later was TRUE, and there
					were modifications by the transaction;
					in that case we must flush the log
					in trx_commit_complete_for_mysql() */
	ulint		duplicates;	/*!< TRX_DUP_IGNORE | TRX_DUP_REPLACE */
	ibool		has_search_latch;
					/* TRUE if this trx has latched any
					search system latch in S-mode */
	ulint		deadlock_mark;	/*!< a mark field used in deadlock
					checking algorithm.  */
	trx_dict_op_t	dict_operation;	/**< @see enum trx_dict_op */

	/* Fields protected by the srv_conc_mutex. */
	ulint		declared_to_be_inside_innodb;
					/* this is TRUE if we have declared
					this transaction in
					srv_conc_enter_innodb to be inside the
					InnoDB engine */

	/* Fields protected by dict_operation_lock. The very latch
	it is used to track. */
	ulint		dict_operation_lock_mode;
					/*!< 0, RW_S_LATCH, or RW_X_LATCH:
					the latch mode trx currently holds
					on dict_operation_lock */

	/* All the next fields are protected by the kernel mutex, except the
	undo logs which are protected by undo_mutex */
	ulint		is_purge;	/*!< 0=user transaction, 1=purge */
	ulint		is_recovered;	/*!< 0=normal transaction,
					1=recovered, must be rolled back */
	ulint		que_state;	/*!< valid when conc_state
					== TRX_ACTIVE: TRX_QUE_RUNNING,
					TRX_QUE_LOCK_WAIT, ... */
	ulint		handling_signals;/* this is TRUE as long as the trx
					is handling signals */
	time_t		start_time;	/*!< time the trx object was created
					or the state last time became
					TRX_ACTIVE */
	trx_id_t	id;		/*!< transaction id */
	XID		xid;		/*!< X/Open XA transaction
					identification to identify a
					transaction branch */
	trx_id_t	no;		/*!< transaction serialization number ==
					max trx id when the transaction is
					moved to COMMITTED_IN_MEMORY state */
	ib_uint64_t	commit_lsn;	/*!< lsn at the time of the commit */
	table_id_t	table_id;	/*!< Table to drop iff dict_operation
					is TRUE, or 0. */
	/*------------------------------*/
	void*		mysql_thd;	/*!< MySQL thread handle corresponding
					to this trx, or NULL */
	const char*	mysql_log_file_name;
					/* if MySQL binlog is used, this field
					contains a pointer to the latest file
					name; this is NULL if binlog is not
					used */
	ib_int64_t	mysql_log_offset;/* if MySQL binlog is used, this field
					contains the end offset of the binlog
					entry */
	const char*	mysql_master_log_file_name;
					/* if the database server is a MySQL
					replication slave, we have here the
					master binlog name up to which
					replication has processed; otherwise
					this is a pointer to a null
					character */
	ib_int64_t	mysql_master_log_pos;
					/* if the database server is a MySQL
					replication slave, this is the
					position in the log file up to which
					replication has processed */
	const char*	mysql_relay_log_file_name;
	ib_int64_t	mysql_relay_log_pos;
	time_t		idle_start;
	ib_int64_t	last_stmt_start;
	/*------------------------------*/
	ulint		n_mysql_tables_in_use; /* number of Innobase tables
					used in the processing of the current
					SQL statement in MySQL */
	ulint		mysql_n_tables_locked;
					/* how many tables the current SQL
					statement uses, except those
					in consistent read */
	ulint		search_latch_timeout;
					/* If we notice that someone is
					waiting for our S-lock on the search
					latch to be released, we wait in
					row0sel.c for BTR_SEA_TIMEOUT new
					searches until we try to keep
					the search latch again over
					calls from MySQL; this is intended
					to reduce contention on the search
					latch */
	/*------------------------------*/
	ulint		n_tickets_to_enter_innodb;
					/* this can be > 0 only when
					declared_to_... is TRUE; when we come
					to srv_conc_innodb_enter, if the value
					here is > 0, we decrement this by 1 */
	/*------------------------------*/
	UT_LIST_NODE_T(trx_t)
			trx_list;	/*!< list of transactions */
	UT_LIST_NODE_T(trx_t)
			mysql_trx_list;	/*!< list of transactions created for
					MySQL */
	UT_LIST_NODE_T(trx_t)
			trx_serial_list;/*!< list node for
					trx_sys->trx_serial_list */
	/*------------------------------*/
	ulint		error_state;	/*!< 0 if no error, otherwise error
					number; NOTE That ONLY the thread
					doing the transaction is allowed to
					set this field: this is NOT protected
					by the kernel mutex */
	const dict_index_t*error_info;	/*!< if the error number indicates a
					duplicate key error, a pointer to
					the problematic index is stored here */
	ulint		error_key_num;	/*!< if the index creation fails to a
					duplicate key error, a mysql key
					number of that index is stored here */
	sess_t*		sess;		/*!< session of the trx, NULL if none */
	que_t*		graph;		/*!< query currently run in the session,
					or NULL if none; NOTE that the query
					belongs to the session, and it can
					survive over a transaction commit, if
					it is a stored procedure with a COMMIT
					WORK statement, for instance */
	ulint		n_active_thrs;	/*!< number of active query threads */
	que_t*		graph_before_signal_handling;
					/* value of graph when signal handling
					for this trx started: this is used to
					return control to the original query
					graph for error processing */
	trx_sig_t	sig;		/*!< one signal object can be allocated
					in this space, avoiding mem_alloc */
	UT_LIST_BASE_NODE_T(trx_sig_t)
			signals;	/*!< queue of processed or pending
					signals to the trx */
	UT_LIST_BASE_NODE_T(trx_sig_t)
			reply_signals;	/*!< list of signals sent by the query
					threads of this trx for which a thread
					is waiting for a reply; if this trx is
					killed, the reply requests in the list
					must be canceled */
	/*------------------------------*/
	lock_t*		wait_lock;	/*!< if trx execution state is
					TRX_QUE_LOCK_WAIT, this points to
					the lock request, otherwise this is
					NULL */
	ibool		was_chosen_as_deadlock_victim;
					/* when the transaction decides to wait
					for a lock, it sets this to FALSE;
					if another transaction chooses this
					transaction as a victim in deadlock
					resolution, it sets this to TRUE */
	time_t		wait_started;	/*!< lock wait started at this time */
	UT_LIST_BASE_NODE_T(que_thr_t)
			wait_thrs;	/*!< query threads belonging to this
					trx that are in the QUE_THR_LOCK_WAIT
					state */
	/*------------------------------*/
	mem_heap_t*	lock_heap;	/*!< memory heap for the locks of the
					transaction */
	UT_LIST_BASE_NODE_T(lock_t)
			trx_locks;	/*!< locks reserved by the transaction */
	/*------------------------------*/
	read_view_t*	global_read_view;
					/* consistent read view associated
					to a transaction or NULL */
	read_view_t*	read_view;	/*!< consistent read view used in the
					transaction or NULL, this read view
					if defined can be normal read view
					associated to a transaction (i.e.
					same as global_read_view) or read view
					associated to a cursor */
	read_view_t*	prebuilt_view;	/* pre-built view array */
	/*------------------------------*/
	UT_LIST_BASE_NODE_T(trx_named_savept_t)
			trx_savepoints;	/*!< savepoints set with SAVEPOINT ...,
					oldest first */
	/*------------------------------*/
	mutex_t		undo_mutex;	/*!< mutex protecting the fields in this
					section (down to undo_no_arr), EXCEPT
					last_sql_stat_start, which can be
					accessed only when we know that there
					cannot be any activity in the undo
					logs! */
	undo_no_t	undo_no;	/*!< next undo log record number to
					assign; since the undo log is
					private for a transaction, this
					is a simple ascending sequence
					with no gaps; thus it represents
					the number of modified/inserted
					rows in a transaction */
	trx_savept_t	last_sql_stat_start;
					/* undo_no when the last sql statement
					was started: in case of an error, trx
					is rolled back down to this undo
					number; see note at undo_mutex! */
	trx_rseg_t*	rseg;		/*!< rollback segment assigned to the
					transaction, or NULL if not assigned
					yet */
	trx_undo_t*	insert_undo;	/*!< pointer to the insert undo log, or
					NULL if no inserts performed yet */
	trx_undo_t*	update_undo;	/*!< pointer to the update undo log, or
					NULL if no update performed yet */
	undo_no_t	roll_limit;	/*!< least undo number to undo during
					a rollback */
	ulint		pages_undone;	/*!< number of undo log pages undone
					since the last undo log truncation */
	trx_undo_arr_t*	undo_no_arr;	/*!< array of undo numbers of undo log
					records which are currently processed
					by a rollback operation */
	/*------------------------------*/
	ulint		n_autoinc_rows;	/*!< no. of AUTO-INC rows required for
					an SQL statement. This is useful for
					multi-row INSERTs */
	ib_vector_t*    autoinc_locks;  /* AUTOINC locks held by this
					transaction. Note that these are
					also in the lock list trx_locks. This
					vector needs to be freed explicitly
					when the trx_t instance is desrtoyed */
	/*------------------------------*/
	char detailed_error[256];	/*!< detailed error message for last
					error, or empty. */
	/*------------------------------*/
	ulint		io_reads;
	ib_uint64_t	io_read;
	ulint		io_reads_wait_timer;
	ib_uint64_t	lock_que_wait_ustarted;
	ulint           lock_que_wait_timer;
	ulint           innodb_que_wait_timer;
	ulint           distinct_page_access;
#define	DPAH_SIZE	8192
	byte*		distinct_page_access_hash;
	ibool		take_stats;
};

#define TRX_MAX_N_THREADS	32	/* maximum number of
					concurrent threads running a
					single operation of a
					transaction, e.g., a parallel
					query */
/* Transaction concurrency states (trx->conc_state) */
#define	TRX_NOT_STARTED		0
#define	TRX_ACTIVE		1
#define	TRX_COMMITTED_IN_MEMORY	2
#define	TRX_PREPARED		3	/* Support for 2PC/XA */

/* Transaction execution states when trx->conc_state == TRX_ACTIVE */
#define TRX_QUE_RUNNING		0	/* transaction is running */
#define TRX_QUE_LOCK_WAIT	1	/* transaction is waiting for a lock */
#define TRX_QUE_ROLLING_BACK	2	/* transaction is rolling back */
#define TRX_QUE_COMMITTING	3	/* transaction is committing */

/* Transaction isolation levels (trx->isolation_level) */
#define TRX_ISO_READ_UNCOMMITTED	0	/* dirty read: non-locking
						SELECTs are performed so that
						we do not look at a possible
						earlier version of a record;
						thus they are not 'consistent'
						reads under this isolation
						level; otherwise like level
						2 */

#define TRX_ISO_READ_COMMITTED		1	/* somewhat Oracle-like
						isolation, except that in
						range UPDATE and DELETE we
						must block phantom rows
						with next-key locks;
						SELECT ... FOR UPDATE and ...
						LOCK IN SHARE MODE only lock
						the index records, NOT the
						gaps before them, and thus
						allow free inserting;
						each consistent read reads its
						own snapshot */

#define TRX_ISO_REPEATABLE_READ		2	/* this is the default;
						all consistent reads in the
						same trx read the same
						snapshot;
						full next-key locking used
						in locking reads to block
						insertions into gaps */

#define TRX_ISO_SERIALIZABLE		3	/* all plain SELECTs are
						converted to LOCK IN SHARE
						MODE reads */

/* Treatment of duplicate values (trx->duplicates; for example, in inserts).
Multiple flags can be combined with bitwise OR. */
#define TRX_DUP_IGNORE	1	/* duplicate rows are to be updated */
#define TRX_DUP_REPLACE	2	/* duplicate rows are to be replaced */


/* Types of a trx signal */
#define TRX_SIG_NO_SIGNAL		0
#define TRX_SIG_TOTAL_ROLLBACK		1
#define TRX_SIG_ROLLBACK_TO_SAVEPT	2
#define TRX_SIG_COMMIT			3
#define	TRX_SIG_ERROR_OCCURRED		4
#define TRX_SIG_BREAK_EXECUTION		5

/* Sender types of a signal */
#define TRX_SIG_SELF		0	/* sent by the session itself, or
					by an error occurring within this
					session */
#define TRX_SIG_OTHER_SESS	1	/* sent by another session (which
					must hold rights to this) */

/** Commit node states */
enum commit_node_state {
	COMMIT_NODE_SEND = 1,	/*!< about to send a commit signal to
				the transaction */
	COMMIT_NODE_WAIT	/*!< commit signal sent to the transaction,
				waiting for completion */
};

/** Commit command node in a query graph */
struct commit_node_struct{
	que_common_t	common;	/*!< node type: QUE_NODE_COMMIT */
	enum commit_node_state
			state;	/*!< node execution state */
};



#ifndef UNIV_NONINL
#include "trx0trx.ic"
#endif
#endif /* !UNIV_HOTBACKUP */

#endif