text: /******************************************************
  The transaction
  
  (c) 1996 Innobase Oy
  
  Created 3/26/1996 Heikki Tuuri
  *******************************************************/
  
  #include "trx0trx.h"
  
  #ifdef UNIV_NONINL
  #include "trx0trx.ic"
  #endif
  
  #include "trx0undo.h"
  #include "trx0rseg.h"
  #include "log0log.h"
  #include "que0que.h"
  #include "lock0lock.h"
  #include "trx0roll.h"
  #include "usr0sess.h"
  #include "read0read.h"
  #include "srv0srv.h"
  #include "thr0loc.h"
  #include "btr0sea.h"
  #include "os0proc.h"
  #include "trx0xa.h"
  #include "ha_prototypes.h"
  
  /* Copy of the prototype for innobase_mysql_print_thd: this
  copy MUST be equal to the one in mysql/sql/ha_innodb.cc ! */
  
  void innobase_mysql_print_thd(
  	FILE*	f,
  	void*	thd,
  	ulint	max_query_len);
  
  /* Dummy session used currently in MySQL interface */
  sess_t*		trx_dummy_sess = NULL;
  
  /* Number of transactions currently allocated for MySQL: protected by
  the kernel mutex */
  ulint	trx_n_mysql_transactions = 0;
  /* Number of transactions currently in the XA PREPARED state: protected by
  the kernel mutex */
  ulint	trx_n_prepared = 0;
  
  /*****************************************************************
  Starts the transaction if it is not yet started. */
  
  void
  trx_start_if_not_started_noninline(
  /*===============================*/
  	trx_t*	trx) /* in: transaction */
  {
  	trx_start_if_not_started(trx);
  }
  
  /*****************************************************************
  Set detailed error message for the transaction. */
  
  void
  trx_set_detailed_error(
  /*===================*/
  	trx_t*		trx,	/* in: transaction struct */
  	const char*	msg)	/* in: detailed error message */
  {
  	ut_strlcpy(trx->detailed_error, msg, sizeof(trx->detailed_error));
  }
  
  /*****************************************************************
  Set detailed error message for the transaction from a file. Note that the
  file is rewinded before reading from it. */
  
  void
  trx_set_detailed_error_from_file(
  /*=============================*/
  	trx_t*	trx,	/* in: transaction struct */
  	FILE*	file)	/* in: file to read message from */
  {
  	os_file_read_string(file, trx->detailed_error,
  			    sizeof(trx->detailed_error));
  }
  
  /********************************************************************
  Retrieves the error_info field from a trx. */
  
  void*
  trx_get_error_info(
  /*===============*/
  			/* out: the error info */
  	trx_t*	trx)	/* in: trx object */
  {
  	return(trx->error_info);
  }
  
  /********************************************************************
  Creates and initializes a transaction object. */
  
  trx_t*
  trx_create(
  /*=======*/
  			/* out, own: the transaction */
  	sess_t*	sess)	/* in: session or NULL */
  {
  	trx_t*	trx;
  
  	ut_ad(mutex_own(&kernel_mutex));
  
  	trx = mem_alloc(sizeof(trx_t));
  
  	trx->magic_n = TRX_MAGIC_N;
  
  	trx->op_info = "";
  
  	trx->is_purge = 0;
  	trx->conc_state = TRX_NOT_STARTED;
  	trx->start_time = time(NULL);
  
  	trx->isolation_level = TRX_ISO_REPEATABLE_READ;
  
  	trx->id = ut_dulint_zero;
  	trx->no = ut_dulint_max;
  
  	trx->support_xa = TRUE;
  
  	trx->check_foreigns = TRUE;
  	trx->check_unique_secondary = TRUE;
  
  	trx->flush_log_later = FALSE;
  	trx->must_flush_log_later = FALSE;
  
  	trx->dict_operation = FALSE;
  
  	trx->mysql_thd = NULL;
  	trx->mysql_query_str = NULL;
  	trx->mysql_query_len = NULL;
  
  	trx->active_trans = 0;
  	trx->duplicates = 0;
  
  	trx->n_mysql_tables_in_use = 0;
  	trx->mysql_n_tables_locked = 0;
  
  	trx->mysql_log_file_name = NULL;
  	trx->mysql_log_offset = 0;
  
  	mutex_create(&trx->undo_mutex, SYNC_TRX_UNDO);
  
  	trx->rseg = NULL;
  
  	trx->undo_no = ut_dulint_zero;
  	trx->last_sql_stat_start.least_undo_no = ut_dulint_zero;
  	trx->insert_undo = NULL;
  	trx->update_undo = NULL;
  	trx->undo_no_arr = NULL;
  
  	trx->error_state = DB_SUCCESS;
  	trx->detailed_error[0] = '\0';
  
  	trx->sess = sess;
  	trx->que_state = TRX_QUE_RUNNING;
  	trx->n_active_thrs = 0;
  
  	trx->handling_signals = FALSE;
  
  	UT_LIST_INIT(trx->signals);
  	UT_LIST_INIT(trx->reply_signals);
  
  	trx->graph = NULL;
  
  	trx->wait_lock = NULL;
  	trx->was_chosen_as_deadlock_victim = FALSE;
  	UT_LIST_INIT(trx->wait_thrs);
  
  	trx->lock_heap = mem_heap_create_in_buffer(256);
  	UT_LIST_INIT(trx->trx_locks);
  
  	UT_LIST_INIT(trx->trx_savepoints);
  
  	trx->dict_operation_lock_mode = 0;
  	trx->has_search_latch = FALSE;
  	trx->search_latch_timeout = BTR_SEA_TIMEOUT;
  
  	trx->declared_to_be_inside_innodb = FALSE;
  	trx->n_tickets_to_enter_innodb = 0;
  
  	trx->auto_inc_lock = NULL;
  
  	trx->global_read_view_heap = mem_heap_create(256);
  	trx->global_read_view = NULL;
  	trx->read_view = NULL;
  
  	/* Set X/Open XA transaction identification to NULL */
  	memset(&trx->xid, 0, sizeof(trx->xid));
  	trx->xid.formatID = -1;
  
  	trx->n_autoinc_rows = 0;
  
  	return(trx);
  }
  
  /************************************************************************
  Creates a transaction object for MySQL. */
  
  trx_t*
  trx_allocate_for_mysql(void)
  /*========================*/
  				/* out, own: transaction object */
  {
  	trx_t*	trx;
  
  	mutex_enter(&kernel_mutex);
  
  	/* Open a dummy session */
  
  	if (!trx_dummy_sess) {
  		trx_dummy_sess = sess_open();
  	}
  
  	trx = trx_create(trx_dummy_sess);
  
  	trx_n_mysql_transactions++;
  
  	UT_LIST_ADD_FIRST(mysql_trx_list, trx_sys->mysql_trx_list, trx);
  
  	mutex_exit(&kernel_mutex);
  
  	trx->mysql_thread_id = os_thread_get_curr_id();
  
  	trx->mysql_process_no = os_proc_get_number();
  
  	return(trx);
  }
  
  /************************************************************************
  Creates a transaction object for background operations by the master thread. */
  
  trx_t*
  trx_allocate_for_background(void)
  /*=============================*/
  				/* out, own: transaction object */
  {
  	trx_t*	trx;
  
  	mutex_enter(&kernel_mutex);
  
  	/* Open a dummy session */
  
  	if (!trx_dummy_sess) {
  		trx_dummy_sess = sess_open();
  	}
  
  	trx = trx_create(trx_dummy_sess);
  
  	mutex_exit(&kernel_mutex);
  
  	return(trx);
  }
  
  /************************************************************************
  Releases the search latch if trx has reserved it. */
  
  void
  trx_search_latch_release_if_reserved(
  /*=================================*/
  	trx_t*	   trx) /* in: transaction */
  {
  	if (trx->has_search_latch) {
  		rw_lock_s_unlock(&btr_search_latch);
  
  		trx->has_search_latch = FALSE;
  	}
  }
  
  /************************************************************************
  Frees a transaction object. */
  
  void
  trx_free(
  /*=====*/
  	trx_t*	trx)	/* in, own: trx object */
  {
  	ut_ad(mutex_own(&kernel_mutex));
  
  	if (trx->declared_to_be_inside_innodb) {
  		ut_print_timestamp(stderr);
  		fputs("  InnoDB: Error: Freeing a trx which is declared"
  		      " to be processing\n"
  		      "InnoDB: inside InnoDB.\n", stderr);
  		trx_print(stderr, trx, 600);
  		putc('\n', stderr);
  
  		/* This is an error but not a fatal error. We must keep
  		the counters like srv_conc_n_threads accurate. */
  		srv_conc_force_exit_innodb(trx);
  	}
  
  	if (trx->n_mysql_tables_in_use != 0
  	    || trx->mysql_n_tables_locked != 0) {
  
  		ut_print_timestamp(stderr);
  		fprintf(stderr,
  			"  InnoDB: Error: MySQL is freeing a thd\n"
  			"InnoDB: though trx->n_mysql_tables_in_use is %lu\n"
  			"InnoDB: and trx->mysql_n_tables_locked is %lu.\n",
  			(ulong)trx->n_mysql_tables_in_use,
  			(ulong)trx->mysql_n_tables_locked);
  
  		trx_print(stderr, trx, 600);
  
  		ut_print_buf(stderr, trx, sizeof(trx_t));
  	}
  
  	ut_a(trx->magic_n == TRX_MAGIC_N);
  
  	trx->magic_n = 11112222;
  
  	ut_a(trx->conc_state == TRX_NOT_STARTED);
  
  	mutex_free(&(trx->undo_mutex));
  
  	ut_a(trx->insert_undo == NULL);
  	ut_a(trx->update_undo == NULL);
  
  	if (trx->undo_no_arr) {
  		trx_undo_arr_free(trx->undo_no_arr);
  	}
  
  	ut_a(UT_LIST_GET_LEN(trx->signals) == 0);
  	ut_a(UT_LIST_GET_LEN(trx->reply_signals) == 0);
  
  	ut_a(trx->wait_lock == NULL);
  	ut_a(UT_LIST_GET_LEN(trx->wait_thrs) == 0);
  
  	ut_a(!trx->has_search_latch);
  	ut_a(!trx->auto_inc_lock);
  
  	ut_a(trx->dict_operation_lock_mode == 0);
  
  	if (trx->lock_heap) {
  		mem_heap_free(trx->lock_heap);
  	}
  
  	ut_a(UT_LIST_GET_LEN(trx->trx_locks) == 0);
  
  	if (trx->global_read_view_heap) {
  		mem_heap_free(trx->global_read_view_heap);
  	}
  
  	trx->global_read_view = NULL;
  
  	ut_a(trx->read_view == NULL);
  
  	mem_free(trx);
  }
  
  /************************************************************************
  Frees a transaction object for MySQL. */
  
  void
  trx_free_for_mysql(
  /*===============*/
  	trx_t*	trx)	/* in, own: trx object */
  {
  	mutex_enter(&kernel_mutex);
  
  	UT_LIST_REMOVE(mysql_trx_list, trx_sys->mysql_trx_list, trx);
  
  	trx_free(trx);
  
  	ut_a(trx_n_mysql_transactions > 0);
  
  	trx_n_mysql_transactions--;
  
  	mutex_exit(&kernel_mutex);
  }
  
  /************************************************************************
  Frees a transaction object of a background operation of the master thread. */
  
  void
  trx_free_for_background(
  /*====================*/
  	trx_t*	trx)	/* in, own: trx object */
  {
  	mutex_enter(&kernel_mutex);
  
  	trx_free(trx);
  
  	mutex_exit(&kernel_mutex);
  }
  
  /********************************************************************
  Inserts the trx handle in the trx system trx list in the right position.
  The list is sorted on the trx id so that the biggest id is at the list
  start. This function is used at the database startup to insert incomplete
  transactions to the list. */
  static
  void
  trx_list_insert_ordered(
  /*====================*/
  	trx_t*	trx)	/* in: trx handle */
  {
  	trx_t*	trx2;
  
  	ut_ad(mutex_own(&kernel_mutex));
  
  	trx2 = UT_LIST_GET_FIRST(trx_sys->trx_list);
  
  	while (trx2 != NULL) {
  		if (ut_dulint_cmp(trx->id, trx2->id) >= 0) {
  
  			ut_ad(ut_dulint_cmp(trx->id, trx2->id) == 1);
  			break;
  		}
  		trx2 = UT_LIST_GET_NEXT(trx_list, trx2);
  	}
  
  	if (trx2 != NULL) {
  		trx2 = UT_LIST_GET_PREV(trx_list, trx2);
  
  		if (trx2 == NULL) {
  			UT_LIST_ADD_FIRST(trx_list, trx_sys->trx_list, trx);
  		} else {
  			UT_LIST_INSERT_AFTER(trx_list, trx_sys->trx_list,
  					     trx2, trx);
  		}
  	} else {
  		UT_LIST_ADD_LAST(trx_list, trx_sys->trx_list, trx);
  	}
  }
  
  /********************************************************************
  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. */
  
  void
  trx_lists_init_at_db_start(void)
  /*============================*/
  {
  	trx_rseg_t*	rseg;
  	trx_undo_t*	undo;
  	trx_t*		trx;
  
  	UT_LIST_INIT(trx_sys->trx_list);
  
  	/* Look from the rollback segments if there exist undo logs for
  	transactions */
  
  	rseg = UT_LIST_GET_FIRST(trx_sys->rseg_list);
  
  	while (rseg != NULL) {
  		undo = UT_LIST_GET_FIRST(rseg->insert_undo_list);
  
  		while (undo != NULL) {
  
  			trx = trx_create(NULL);
  
  			trx->id = undo->trx_id;
  			trx->xid = undo->xid;
  			trx->insert_undo = undo;
  			trx->rseg = rseg;
  
  			if (undo->state != TRX_UNDO_ACTIVE) {
  
  				/* Prepared transactions are left in
  				the prepared state waiting for a
  				commit or abort decision from MySQL */
  
  				if (undo->state == TRX_UNDO_PREPARED) {
  
  					fprintf(stderr,
  						"InnoDB: Transaction %lu %lu"
  						" was in the"
  						" XA prepared state.\n",
  						ut_dulint_get_high(trx->id),
  						ut_dulint_get_low(trx->id));
  
  					if (srv_force_recovery == 0) {
  
  						trx->conc_state = TRX_PREPARED;
  						trx_n_prepared++;
  					} else {
  						fprintf(stderr,
  							"InnoDB: Since"
  							" innodb_force_recovery"
  							" > 0, we will"
  							" rollback it"
  							" anyway.\n");
  
  						trx->conc_state = TRX_ACTIVE;
  					}
  				} else {
  					trx->conc_state
  						= TRX_COMMITTED_IN_MEMORY;
  				}
  
  				/* We give a dummy value for the trx no;
  				this should have no relevance since purge
  				is not interested in committed transaction
  				numbers, unless they are in the history
  				list, in which case it looks the number
  				from the disk based undo log structure */
  
  				trx->no = trx->id;
  			} else {
  				trx->conc_state = TRX_ACTIVE;
  
  				/* A running transaction always has the number
  				field inited to ut_dulint_max */
  
  				trx->no = ut_dulint_max;
  			}
  
  			if (undo->dict_operation) {
  				trx->dict_operation = undo->dict_operation;
  				trx->table_id = undo->table_id;
  			}
  
  			if (!undo->empty) {
  				trx->undo_no = ut_dulint_add(undo->top_undo_no,
  							     1);
  			}
  
  			trx_list_insert_ordered(trx);
  
  			undo = UT_LIST_GET_NEXT(undo_list, undo);
  		}
  
  		undo = UT_LIST_GET_FIRST(rseg->update_undo_list);
  
  		while (undo != NULL) {
  			trx = trx_get_on_id(undo->trx_id);
  
  			if (NULL == trx) {
  				trx = trx_create(NULL);
  
  				trx->id = undo->trx_id;
  				trx->xid = undo->xid;
  
  				if (undo->state != TRX_UNDO_ACTIVE) {
  
  					/* Prepared transactions are left in
  					the prepared state waiting for a
  					commit or abort decision from MySQL */
  
  					if (undo->state == TRX_UNDO_PREPARED) {
  						fprintf(stderr,
  							"InnoDB: Transaction"
  							" %lu %lu was in the"
  							" XA prepared state.\n",
  							ut_dulint_get_high(
  								trx->id),
  							ut_dulint_get_low(
  								trx->id));
  
  						if (srv_force_recovery == 0) {
  
  							trx->conc_state
  								= TRX_PREPARED;
  							trx_n_prepared++;
  						} else {
  							fprintf(stderr,
  								"InnoDB: Since"
  								" innodb_force_recovery"
  								" > 0, we will"
  								" rollback it"
  								" anyway.\n");
  
  							trx->conc_state
  								= TRX_ACTIVE;
  						}
  					} else {
  						trx->conc_state
  							= TRX_COMMITTED_IN_MEMORY;
  					}
  
  					/* We give a dummy value for the trx
  					number */
  
  					trx->no = trx->id;
  				} else {
  					trx->conc_state = TRX_ACTIVE;
  
  					/* A running transaction always has
  					the number field inited to
  					ut_dulint_max */
  
  					trx->no = ut_dulint_max;
  				}
  
  				trx->rseg = rseg;
  				trx_list_insert_ordered(trx);
  
  				if (undo->dict_operation) {
  					trx->dict_operation
  						= undo->dict_operation;
  					trx->table_id = undo->table_id;
  				}
  			}
  
  			trx->update_undo = undo;
  
  			if ((!undo->empty)
  			    && (ut_dulint_cmp(undo->top_undo_no,
  					      trx->undo_no) >= 0)) {
  
  				trx->undo_no = ut_dulint_add(undo->top_undo_no,
  							     1);
  			}
  
  			undo = UT_LIST_GET_NEXT(undo_list, undo);
  		}
  
  		rseg = UT_LIST_GET_NEXT(rseg_list, rseg);
  	}
  }
  
  /**********************************************************************
  Assigns a rollback segment to a transaction in a round-robin fashion.
  Skips the SYSTEM rollback segment if another is available. */
  UNIV_INLINE
  ulint
  trx_assign_rseg(void)
  /*=================*/
  			/* out: assigned rollback segment id */
  {
  	trx_rseg_t*	rseg	= trx_sys->latest_rseg;
  
  	ut_ad(mutex_own(&kernel_mutex));
  loop:
  	/* Get next rseg in a round-robin fashion */
  
  	rseg = UT_LIST_GET_NEXT(rseg_list, rseg);
  
  	if (rseg == NULL) {
  		rseg = UT_LIST_GET_FIRST(trx_sys->rseg_list);
  	}
  
  	/* If it is the SYSTEM rollback segment, and there exist others, skip
  	it */
  
  	if ((rseg->id == TRX_SYS_SYSTEM_RSEG_ID)
  	    && (UT_LIST_GET_LEN(trx_sys->rseg_list) > 1)) {
  		goto loop;
  	}
  
  	trx_sys->latest_rseg = rseg;
  
  	return(rseg->id);
  }
  
  /********************************************************************
  Starts a new transaction. */
  
  ibool
  trx_start_low(
  /*==========*/
  			/* out: TRUE */
  	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 */
  {
  	trx_rseg_t*	rseg;
  
  	ut_ad(mutex_own(&kernel_mutex));
  	ut_ad(trx->rseg == NULL);
  
  	if (trx->is_purge) {
  		trx->id = ut_dulint_zero;
  		trx->conc_state = TRX_ACTIVE;
  		trx->start_time = time(NULL);
  
  		return(TRUE);
  	}
  
  	ut_ad(trx->conc_state != TRX_ACTIVE);
  
  	if (rseg_id == ULINT_UNDEFINED) {
  
  		rseg_id = trx_assign_rseg();
  	}
  
  	rseg = trx_sys_get_nth_rseg(trx_sys, rseg_id);
  
  	trx->id = trx_sys_get_new_trx_id();
  
  	/* The initial value for trx->no: ut_dulint_max is used in
  	read_view_open_now: */
  
  	trx->no = ut_dulint_max;
  
  	trx->rseg = rseg;
  
  	trx->conc_state = TRX_ACTIVE;
  	trx->start_time = time(NULL);
  
  	UT_LIST_ADD_FIRST(trx_list, trx_sys->trx_list, trx);
  
  	return(TRUE);
  }
  
  /********************************************************************
  Starts a new transaction. */
  
  ibool
  trx_start(
  /*======*/
  			/* out: TRUE */
  	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 */
  {
  	ibool	ret;
  
  	mutex_enter(&kernel_mutex);
  
  	ret = trx_start_low(trx, rseg_id);
  
  	mutex_exit(&kernel_mutex);
  
  	return(ret);
  }
  
  /********************************************************************
  Commits a transaction. */
  
  void
  trx_commit_off_kernel(
  /*==================*/
  	trx_t*	trx)	/* in: transaction */
  {
  	page_t*		update_hdr_page;
  	dulint		lsn;
  	trx_rseg_t*	rseg;
  	trx_undo_t*	undo;
  	ibool		must_flush_log	= FALSE;
  	mtr_t		mtr;
  
  	ut_ad(mutex_own(&kernel_mutex));
  
  	trx->must_flush_log_later = FALSE;
  
  	rseg = trx->rseg;
  
  	if (trx->insert_undo != NULL || trx->update_undo != NULL) {
  
  		mutex_exit(&kernel_mutex);
  
  		mtr_start(&mtr);
  
  		must_flush_log = TRUE;
  
  		/* Change the undo log segment states from TRX_UNDO_ACTIVE
  		to some other state: these modifications to the file data
  		structure define the transaction as committed in the file
  		based world, at the serialization point of the log sequence
  		number lsn obtained below. */
  
  		mutex_enter(&(rseg->mutex));
  
  		if (trx->insert_undo != NULL) {
  			trx_undo_set_state_at_finish(
  				rseg, trx, trx->insert_undo, &mtr);
  		}
  
  		undo = trx->update_undo;
  
  		if (undo) {
  			mutex_enter(&kernel_mutex);
  			trx->no = trx_sys_get_new_trx_no();
  
  			mutex_exit(&kernel_mutex);
  
  			/* It is not necessary to obtain trx->undo_mutex here
  			because only a single OS thread is allowed to do the
  			transaction commit for this transaction. */
  
  			update_hdr_page = trx_undo_set_state_at_finish(
  				rseg, trx, undo, &mtr);
  
  			/* We have to do the cleanup for the update log while
  			holding the rseg mutex because update log headers
  			have to be put to the history list in the order of
  			the trx number. */
  
  			trx_undo_update_cleanup(trx, update_hdr_page, &mtr);
  		}
  
  		mutex_exit(&(rseg->mutex));
  
  		/* Update the latest MySQL binlog name and offset info
  		in trx sys header if MySQL binlogging is on or the database
  		server is a MySQL replication slave */
  
  		if (trx->mysql_log_file_name
  		    && trx->mysql_log_file_name[0] != '\0') {
  			trx_sys_update_mysql_binlog_offset(
  				trx->mysql_log_file_name,
  				trx->mysql_log_offset,
  				TRX_SYS_MYSQL_LOG_INFO, &mtr);
  			trx->mysql_log_file_name = NULL;
  		}
  
  		/* The following call commits the mini-transaction, making the
  		whole transaction committed in the file-based world, at this
  		log sequence number. The transaction becomes 'durable' when
  		we write the log to disk, but in the logical sense the commit
  		in the file-based data structures (undo logs etc.) happens
  		here.
  
  		NOTE that transaction numbers, which are assigned only to
  		transactions with an update undo log, do not necessarily come
  		in exactly the same order as commit lsn's, if the transactions
  		have different rollback segments. To get exactly the same
  		order we should hold the kernel mutex up to this point,
  		adding to to the contention of the kernel mutex. However, if
  		a transaction T2 is able to see modifications made by
  		a transaction T1, T2 will always get a bigger transaction
  		number and a bigger commit lsn than T1. */
  
  		/*--------------*/
  		mtr_commit(&mtr);
  		/*--------------*/
  		lsn = mtr.end_lsn;
  
  		mutex_enter(&kernel_mutex);
  	}
  
  	ut_ad(trx->conc_state == TRX_ACTIVE
  	      || trx->conc_state == TRX_PREPARED);
  	ut_ad(mutex_own(&kernel_mutex));
  
  	if (UNIV_UNLIKELY(trx->conc_state == TRX_PREPARED)) {
  		ut_a(trx_n_prepared > 0);
  		trx_n_prepared--;
  	}
  
  	/* The following assignment makes the transaction committed in memory
  	and makes its changes to data visible to other transactions.
  	NOTE that there is a small discrepancy from the strict formal
  	visibility rules here: a human user of the database can see
  	modifications made by another transaction T even before the necessary
  	log segment has been flushed to the disk. If the database happens to
  	crash before the flush, the user has seen modifications from T which
  	will never be a committed transaction. However, any transaction T2
  	which sees the modifications of the committing transaction T, and
  	which also itself makes modifications to the database, will get an lsn
  	larger than the committing transaction T. In the case where the log
  	flush fails, and T never gets committed, also T2 will never get
  	committed. */
  
  	/*--------------------------------------*/
  	trx->conc_state = TRX_COMMITTED_IN_MEMORY;
  	/*--------------------------------------*/
  
  	lock_release_off_kernel(trx);
  
  	if (trx->global_read_view) {
  		read_view_close(trx->global_read_view);
  		mem_heap_empty(trx->global_read_view_heap);
  		trx->global_read_view = NULL;
  	}
  
  	trx->read_view = NULL;
  
  	if (must_flush_log) {
  
  		mutex_exit(&kernel_mutex);
  
  		if (trx->insert_undo != NULL) {
  
  			trx_undo_insert_cleanup(trx);
  		}
  
  		/* NOTE that we could possibly make a group commit more
  		efficient here: call os_thread_yield here to allow also other
  		trxs to come to commit! */
  
  		/*-------------------------------------*/
  
  		/* Depending on the my.cnf options, we may now write the log
  		buffer to the log files, making the transaction durable if
  		the OS does not crash. We may also flush the log files to
  		disk, making the transaction durable also at an OS crash or a
  		power outage.
  
  		The idea in InnoDB's group commit is that a group of
  		transactions gather behind a trx doing a physical disk write
  		to log files, and when that physical write has been completed,
  		one of those transactions does a write which commits the whole
  		group. Note that this group commit will only bring benefit if
  		there are > 2 users in the database. Then at least 2 users can
  		gather behind one doing the physical log write to disk.
  
  		If we are calling trx_commit() under MySQL's binlog mutex, we
  		will delay possible log write and flush to a separate function
  		trx_commit_complete_for_mysql(), which is only called when the
  		thread has released the binlog mutex. This is to make the
  		group commit algorithm to work. Otherwise, the MySQL binlog
  		mutex would serialize all commits and prevent a group of
  		transactions from gathering. */
  
  		if (trx->flush_log_later) {
  			/* Do nothing yet */
  			trx->must_flush_log_later = TRUE;
  		} else if (srv_flush_log_at_trx_commit == 0) {
  			/* Do nothing */
  		} else if (srv_flush_log_at_trx_commit == 1) {
  			if (srv_unix_file_flush_method == SRV_UNIX_NOSYNC) {
  				/* Write the log but do not flush it to disk */
  
  				log_write_up_to(lsn, LOG_WAIT_ONE_GROUP,
  						FALSE);
  			} else {
  				/* Write the log to the log files AND flush
  				them to disk */
  
  				log_write_up_to(lsn, LOG_WAIT_ONE_GROUP, TRUE);
  			}
  		} else if (srv_flush_log_at_trx_commit == 2) {
  
  			/* Write the log but do not flush it to disk */
  
  			log_write_up_to(lsn, LOG_WAIT_ONE_GROUP, FALSE);
  		} else {
  			ut_error;
  		}
  
  		trx->commit_lsn = lsn;
  
  		/*-------------------------------------*/
  
  		mutex_enter(&kernel_mutex);
  	}
  
  	/* Free all savepoints */
  	trx_roll_free_all_savepoints(trx);
  
  	trx->conc_state = TRX_NOT_STARTED;
  	trx->rseg = NULL;
  	trx->undo_no = ut_dulint_zero;
  	trx->last_sql_stat_start.least_undo_no = ut_dulint_zero;
  	trx->mysql_query_str = NULL;
  	trx->mysql_query_len = NULL;
  
  	ut_ad(UT_LIST_GET_LEN(trx->wait_thrs) == 0);
  	ut_ad(UT_LIST_GET_LEN(trx->trx_locks) == 0);
  
  	UT_LIST_REMOVE(trx_list, trx_sys->trx_list, trx);
  }
  
  /********************************************************************
  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, andf we cannot roll it back. */
  
  void
  trx_cleanup_at_db_startup(
  /*======================*/
  	trx_t*	trx)	/* in: transaction */
  {
  	if (trx->insert_undo != NULL) {
  
  		trx_undo_insert_cleanup(trx);
  	}
  
  	trx->conc_state = TRX_NOT_STARTED;
  	trx->rseg = NULL;
  	trx->undo_no = ut_dulint_zero;
  	trx->last_sql_stat_start.least_undo_no = ut_dulint_zero;
  
  	UT_LIST_REMOVE(trx_list, trx_sys->trx_list, trx);
  }
  
  /************************************************************************
  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. */
  
  read_view_t*
  trx_assign_read_view(
  /*=================*/
  			/* out: consistent read view */
  	trx_t*	trx)	/* in: active transaction */
  {
  	ut_ad(trx->conc_state == TRX_ACTIVE);
  
  	if (trx->read_view) {
  		return(trx->read_view);
  	}
  
  	mutex_enter(&kernel_mutex);
  
  	if (!trx->read_view) {
  		trx->read_view = read_view_open_now(
  			trx->id, trx->global_read_view_heap);
  		trx->global_read_view = trx->read_view;
  	}
  
  	mutex_exit(&kernel_mutex);
  
  	return(trx->read_view);
  }
  
  /********************************************************************
  Commits a transaction. NOTE that the kernel mutex is temporarily released. */
  static
  void
  trx_handle_commit_sig_off_kernel(
  /*=============================*/
  	trx_t*		trx,		/* in: transaction */
  	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 */
  {
  	trx_sig_t*	sig;
  	trx_sig_t*	next_sig;
  
  	ut_ad(mutex_own(&kernel_mutex));
  
  	trx->que_state = TRX_QUE_COMMITTING;
  
  	trx_commit_off_kernel(trx);
  
  	ut_ad(UT_LIST_GET_LEN(trx->wait_thrs) == 0);
  
  	/* Remove all TRX_SIG_COMMIT signals from the signal queue and send
  	reply messages to them */
  
  	sig = UT_LIST_GET_FIRST(trx->signals);
  
  	while (sig != NULL) {
  		next_sig = UT_LIST_GET_NEXT(signals, sig);
  
  		if (sig->type == TRX_SIG_COMMIT) {
  
  			trx_sig_reply(sig, next_thr);
  			trx_sig_remove(trx, sig);
  		}
  
  		sig = next_sig;
  	}
  
  	trx->que_state = TRX_QUE_RUNNING;
  }
  
  /***************************************************************
  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. */
  
  void
  trx_end_lock_wait(
  /*==============*/
  	trx_t*	trx)	/* in: transaction */
  {
  	que_thr_t*	thr;
  
  	ut_ad(mutex_own(&kernel_mutex));
  	ut_ad(trx->que_state == TRX_QUE_LOCK_WAIT);
  
  	thr = UT_LIST_GET_FIRST(trx->wait_thrs);
  
  	while (thr != NULL) {
  		que_thr_end_wait_no_next_thr(thr);
  
  		UT_LIST_REMOVE(trx_thrs, trx->wait_thrs, thr);
  
  		thr = UT_LIST_GET_FIRST(trx->wait_thrs);
  	}
  
  	trx->que_state = TRX_QUE_RUNNING;
  }
  
  /***************************************************************
  Moves the query threads in the lock wait list to the SUSPENDED state and puts
  the transaction to the TRX_QUE_RUNNING state. */
  static
  void
  trx_lock_wait_to_suspended(
  /*=======================*/
  	trx_t*	trx)	/* in: transaction in the TRX_QUE_LOCK_WAIT state */
  {
  	que_thr_t*	thr;
  
  	ut_ad(mutex_own(&kernel_mutex));
  	ut_ad(trx->que_state == TRX_QUE_LOCK_WAIT);
  
  	thr = UT_LIST_GET_FIRST(trx->wait_thrs);
  
  	while (thr != NULL) {
  		thr->state = QUE_THR_SUSPENDED;
  
  		UT_LIST_REMOVE(trx_thrs, trx->wait_thrs, thr);
  
  		thr = UT_LIST_GET_FIRST(trx->wait_thrs);
  	}
  
  	trx->que_state = TRX_QUE_RUNNING;
  }
  
  /***************************************************************
  Moves the query threads in the sig reply wait list of trx to the SUSPENDED
  state. */
  static
  void
  trx_sig_reply_wait_to_suspended(
  /*============================*/
  	trx_t*	trx)	/* in: transaction */
  {
  	trx_sig_t*	sig;
  	que_thr_t*	thr;
  
  	ut_ad(mutex_own(&kernel_mutex));
  
  	sig = UT_LIST_GET_FIRST(trx->reply_signals);
  
  	while (sig != NULL) {
  		thr = sig->receiver;
  
  		ut_ad(thr->state == QUE_THR_SIG_REPLY_WAIT);
  
  		thr->state = QUE_THR_SUSPENDED;
  
  		sig->receiver = NULL;
  
  		UT_LIST_REMOVE(reply_signals, trx->reply_signals, sig);
  
  		sig = UT_LIST_GET_FIRST(trx->reply_signals);
  	}
  }
  
  /*********************************************************************
  Checks the compatibility of a new signal with the other signals in the
  queue. */
  static
  ibool
  trx_sig_is_compatible(
  /*==================*/
  			/* out: TRUE if the signal can be queued */
  	trx_t*	trx,	/* in: trx handle */
  	ulint	type,	/* in: signal type */
  	ulint	sender)	/* in: TRX_SIG_SELF or TRX_SIG_OTHER_SESS */
  {
  	trx_sig_t*	sig;
  
  	ut_ad(mutex_own(&kernel_mutex));
  
  	if (UT_LIST_GET_LEN(trx->signals) == 0) {
  
  		return(TRUE);
  	}
  
  	if (sender == TRX_SIG_SELF) {
  		if (type == TRX_SIG_ERROR_OCCURRED) {
  
  			return(TRUE);
  
  		} else if (type == TRX_SIG_BREAK_EXECUTION) {
  
  			return(TRUE);
  		} else {
  			return(FALSE);
  		}
  	}
  
  	ut_ad(sender == TRX_SIG_OTHER_SESS);
  
  	sig = UT_LIST_GET_FIRST(trx->signals);
  
  	if (type == TRX_SIG_COMMIT) {
  		while (sig != NULL) {
  
  			if (sig->type == TRX_SIG_TOTAL_ROLLBACK) {
  
  				return(FALSE);
  			}
  
  			sig = UT_LIST_GET_NEXT(signals, sig);
  		}
  
  		return(TRUE);
  
  	} else if (type == TRX_SIG_TOTAL_ROLLBACK) {
  		while (sig != NULL) {
  
  			if (sig->type == TRX_SIG_COMMIT) {
  
  				return(FALSE);
  			}
  
  			sig = UT_LIST_GET_NEXT(signals, sig);
  		}
  
  		return(TRUE);
  
  	} else if (type == TRX_SIG_BREAK_EXECUTION) {
  
  		return(TRUE);
  	} else {
  		ut_error;
  
  		return(FALSE);
  	}
  }
  
  /********************************************************************
  Sends a signal to a trx object. */
  
  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 */
  {
  	trx_sig_t*	sig;
  	trx_t*		receiver_trx;
  
  	ut_ad(trx);
  	ut_ad(mutex_own(&kernel_mutex));
  
  	if (!trx_sig_is_compatible(trx, type, sender)) {
  		/* The signal is not compatible with the other signals in
  		the queue: die */
  
  		ut_error;
  	}
  
  	/* Queue the signal object */
  
  	if (UT_LIST_GET_LEN(trx->signals) == 0) {
  
  		/* The signal list is empty: the 'sig' slot must be unused
  		(we improve performance a bit by avoiding mem_alloc) */
  		sig = &(trx->sig);
  	} else {
  		/* It might be that the 'sig' slot is unused also in this
  		case, but we choose the easy way of using mem_alloc */
  
  		sig = mem_alloc(sizeof(trx_sig_t));
  	}
  
  	UT_LIST_ADD_LAST(signals, trx->signals, sig);
  
  	sig->type = type;
  	sig->sender = sender;
  	sig->receiver = receiver_thr;
  
  	if (savept) {
  		sig->savept = *savept;
  	}
  
  	if (receiver_thr) {
  		receiver_trx = thr_get_trx(receiver_thr);
  
  		UT_LIST_ADD_LAST(reply_signals, receiver_trx->reply_signals,
  				 sig);
  	}
  
  	if (trx->sess->state == SESS_ERROR) {
  
  		trx_sig_reply_wait_to_suspended(trx);
  	}
  
  	if ((sender != TRX_SIG_SELF) || (type == TRX_SIG_BREAK_EXECUTION)) {
  		ut_error;
  	}
  
  	/* If there were no other signals ahead in the queue, try to start
  	handling of the signal */
  
  	if (UT_LIST_GET_FIRST(trx->signals) == sig) {
  
  		trx_sig_start_handle(trx, next_thr);
  	}
  }
  
  /********************************************************************
  Ends signal handling. If the session is in the error state, and
  trx->graph_before_signal_handling != NULL, then returns control to the error
  handling routine of the graph (currently just returns the control to the
  graph root which then will send an error message to the client). */
  
  void
  trx_end_signal_handling(
  /*====================*/
  	trx_t*	trx)	/* in: trx */
  {
  	ut_ad(mutex_own(&kernel_mutex));
  	ut_ad(trx->handling_signals == TRUE);
  
  	trx->handling_signals = FALSE;
  
  	trx->graph = trx->graph_before_signal_handling;
  
  	if (trx->graph && (trx->sess->state == SESS_ERROR)) {
  
  		que_fork_error_handle(trx, trx->graph);
  	}
  }
  
  /********************************************************************
  Starts handling of a trx signal. */
  
  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; if the parameter
  					is NULL, it is ignored */
  {
  	trx_sig_t*	sig;
  	ulint		type;
  loop:
  	/* We loop in this function body as long as there are queued signals
  	we can process immediately */
  
  	ut_ad(trx);
  	ut_ad(mutex_own(&kernel_mutex));
  
  	if (trx->handling_signals && (UT_LIST_GET_LEN(trx->signals) == 0)) {
  
  		trx_end_signal_handling(trx);
  
  		return;
  	}
  
  	if (trx->conc_state == TRX_NOT_STARTED) {
  
  		trx_start_low(trx, ULINT_UNDEFINED);
  	}
  
  	/* If the trx is in a lock wait state, moves the waiting query threads
  	to the suspended state */
  
  	if (trx->que_state == TRX_QUE_LOCK_WAIT) {
  
  		trx_lock_wait_to_suspended(trx);
  	}
  
  	/* If the session is in the error state and this trx has threads
  	waiting for reply from signals, moves these threads to the suspended
  	state, canceling wait reservations; note that if the transaction has
  	sent a commit or rollback signal to itself, and its session is not in
  	the error state, then nothing is done here. */
  
  	if (trx->sess->state == SESS_ERROR) {
  		trx_sig_reply_wait_to_suspended(trx);
  	}
  
  	/* If there are no running query threads, we can start processing of a
  	signal, otherwise we have to wait until all query threads of this
  	transaction are aware of the arrival of the signal. */
  
  	if (trx->n_active_thrs > 0) {
  
  		return;
  	}
  
  	if (trx->handling_signals == FALSE) {
  		trx->graph_before_signal_handling = trx->graph;
  
  		trx->handling_signals = TRUE;
  	}
  
  	sig = UT_LIST_GET_FIRST(trx->signals);
  	type = sig->type;
  
  	if (type == TRX_SIG_COMMIT) {
  
  		trx_handle_commit_sig_off_kernel(trx, next_thr);
  
  	} else if ((type == TRX_SIG_TOTAL_ROLLBACK)
  		   || (type == TRX_SIG_ROLLBACK_TO_SAVEPT)) {
  
  		trx_rollback(trx, sig, next_thr);
  
  		/* No further signals can be handled until the rollback
  		completes, therefore we return */
  
  		return;
  
  	} else if (type == TRX_SIG_ERROR_OCCURRED) {
  
  		trx_rollback(trx, sig, next_thr);
  
  		/* No further signals can be handled until the rollback
  		completes, therefore we return */
  
  		return;
  
  	} else if (type == TRX_SIG_BREAK_EXECUTION) {
  
  		trx_sig_reply(sig, next_thr);
  		trx_sig_remove(trx, sig);
  	} else {
  		ut_error;
  	}
  
  	goto loop;
  }
  
  /********************************************************************
  Send the reply message when a signal in the queue of the trx has been
  handled. */
  
  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 */
  {
  	trx_t*	receiver_trx;
  
  	ut_ad(sig);
  	ut_ad(mutex_own(&kernel_mutex));
  
  	if (sig->receiver != NULL) {
  		ut_ad((sig->receiver)->state == QUE_THR_SIG_REPLY_WAIT);
  
  		receiver_trx = thr_get_trx(sig->receiver);
  
  		UT_LIST_REMOVE(reply_signals, receiver_trx->reply_signals,
  			       sig);
  		ut_ad(receiver_trx->sess->state != SESS_ERROR);
  
  		que_thr_end_wait(sig->receiver, next_thr);
  
  		sig->receiver = NULL;
  
  	}
  }
  
  /********************************************************************
  Removes a signal object from the trx signal queue. */
  
  void
  trx_sig_remove(
  /*===========*/
  	trx_t*		trx,	/* in: trx handle */
  	trx_sig_t*	sig)	/* in, own: signal */
  {
  	ut_ad(trx && sig);
  	ut_ad(mutex_own(&kernel_mutex));
  
  	ut_ad(sig->receiver == NULL);
  
  	UT_LIST_REMOVE(signals, trx->signals, sig);
  	sig->type = 0;	/* reset the field to catch possible bugs */
  
  	if (sig != &(trx->sig)) {
  		mem_free(sig);
  	}
  }
  
  /*************************************************************************
  Creates a commit command node struct. */
  
  commit_node_t*
  commit_node_create(
  /*===============*/
  				/* out, own: commit node struct */
  	mem_heap_t*	heap)	/* in: mem heap where created */
  {
  	commit_node_t*	node;
  
  	node = mem_heap_alloc(heap, sizeof(commit_node_t));
  	node->common.type  = QUE_NODE_COMMIT;
  	node->state = COMMIT_NODE_SEND;
  
  	return(node);
  }
  
  /***************************************************************
  Performs an execution step for a commit type node in a query graph. */
  
  que_thr_t*
  trx_commit_step(
  /*============*/
  				/* out: query thread to run next, or NULL */
  	que_thr_t*	thr)	/* in: query thread */
  {
  	commit_node_t*	node;
  	que_thr_t*	next_thr;
  
  	node = thr->run_node;
  
  	ut_ad(que_node_get_type(node) == QUE_NODE_COMMIT);
  
  	if (thr->prev_node == que_node_get_parent(node)) {
  		node->state = COMMIT_NODE_SEND;
  	}
  
  	if (node->state == COMMIT_NODE_SEND) {
  		mutex_enter(&kernel_mutex);
  
  		node->state = COMMIT_NODE_WAIT;
  
  		next_thr = NULL;
  
  		thr->state = QUE_THR_SIG_REPLY_WAIT;
  
  		/* Send the commit signal to the transaction */
  
  		trx_sig_send(thr_get_trx(thr), TRX_SIG_COMMIT, TRX_SIG_SELF,
  			     thr, NULL, &next_thr);
  
  		mutex_exit(&kernel_mutex);
  
  		return(next_thr);
  	}
  
  	ut_ad(node->state == COMMIT_NODE_WAIT);
  
  	node->state = COMMIT_NODE_SEND;
  
  	thr->run_node = que_node_get_parent(node);
  
  	return(thr);
  }
  
  /**************************************************************************
  Does the transaction commit for MySQL. */
  
  ulint
  trx_commit_for_mysql(
  /*=================*/
  			/* out: 0 or error number */
  	trx_t*	trx)	/* in: trx handle */
  {
  	/* Because we do not do the commit by sending an Innobase
  	sig to the transaction, we must here make sure that trx has been
  	started. */
  
  	ut_a(trx);
  
  	trx->op_info = "committing";
  
  	/* If we are doing the XA recovery of prepared transactions, then
  	the transaction object does not have an InnoDB session object, and we
  	set the dummy session that we use for all MySQL transactions. */
  
  	if (trx->sess == NULL) {
  		/* Open a dummy session */
  
  		if (!trx_dummy_sess) {
  			mutex_enter(&kernel_mutex);
  
  			if (!trx_dummy_sess) {
  				trx_dummy_sess = sess_open();
  			}
  
  			mutex_exit(&kernel_mutex);
  		}
  
  		trx->sess = trx_dummy_sess;
  	}
  
  	trx_start_if_not_started(trx);
  
  	mutex_enter(&kernel_mutex);
  
  	trx_commit_off_kernel(trx);
  
  	mutex_exit(&kernel_mutex);
  
  	trx->op_info = "";
  
  	return(0);
  }
  
  /**************************************************************************
  If required, flushes the log to disk if we called trx_commit_for_mysql()
  with trx->flush_log_later == TRUE. */
  
  ulint
  trx_commit_complete_for_mysql(
  /*==========================*/
  			/* out: 0 or error number */
  	trx_t*	trx)	/* in: trx handle */
  {
  	dulint	lsn	= trx->commit_lsn;
  
  	ut_a(trx);
  
  	trx->op_info = "flushing log";
  
  	if (!trx->must_flush_log_later) {
  		/* Do nothing */
  	} else if (srv_flush_log_at_trx_commit == 0) {
  		/* Do nothing */
  	} else if (srv_flush_log_at_trx_commit == 1) {
  		if (srv_unix_file_flush_method == SRV_UNIX_NOSYNC) {
  			/* Write the log but do not flush it to disk */
  
  			log_write_up_to(lsn, LOG_WAIT_ONE_GROUP, FALSE);
  		} else {
  			/* Write the log to the log files AND flush them to
  			disk */
  
  			log_write_up_to(lsn, LOG_WAIT_ONE_GROUP, TRUE);
  		}
  	} else if (srv_flush_log_at_trx_commit == 2) {
  
  		/* Write the log but do not flush it to disk */
  
  		log_write_up_to(lsn, LOG_WAIT_ONE_GROUP, FALSE);
  	} else {
  		ut_error;
  	}
  
  	trx->must_flush_log_later = FALSE;
  
  	trx->op_info = "";
  
  	return(0);
  }
  
  /**************************************************************************
  Marks the latest SQL statement ended. */
  
  void
  trx_mark_sql_stat_end(
  /*==================*/
  	trx_t*	trx)	/* in: trx handle */
  {
  	ut_a(trx);
  
  	if (trx->conc_state == TRX_NOT_STARTED) {
  		trx->undo_no = ut_dulint_zero;
  	}
  
  	trx->last_sql_stat_start.least_undo_no = trx->undo_no;
  }
  
  /**************************************************************************
  Prints info about a transaction to the given file. The caller must own the
  kernel mutex. */
  
  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 */
  {
  	ibool	newline;
  
  	fprintf(f, "TRANSACTION %lu %lu",
  		(ulong) ut_dulint_get_high(trx->id),
  		(ulong) ut_dulint_get_low(trx->id));
  
  	switch (trx->conc_state) {
  	case TRX_NOT_STARTED:
  		fputs(", not started", f);
  		break;
  	case TRX_ACTIVE:
  		fprintf(f, ", ACTIVE %lu sec",
  			(ulong)difftime(time(NULL), trx->start_time));
  		break;
  	case TRX_PREPARED:
  		fprintf(f, ", ACTIVE (PREPARED) %lu sec",
  			(ulong)difftime(time(NULL), trx->start_time));
  		break;
  	case TRX_COMMITTED_IN_MEMORY:
  		fputs(", COMMITTED IN MEMORY", f);
  		break;
  	default:
  		fprintf(f, " state %lu", (ulong) trx->conc_state);
  	}
  
  #ifdef UNIV_LINUX
  	fprintf(f, ", process no %lu", trx->mysql_process_no);
  #endif
  	fprintf(f, ", OS thread id %lu",
  		(ulong) os_thread_pf(trx->mysql_thread_id));
  
  	if (*trx->op_info) {
  		putc(' ', f);
  		fputs(trx->op_info, f);
  	}
  
  	if (trx->is_purge) {
  		fputs(" purge trx", f);
  	}
  
  	if (trx->declared_to_be_inside_innodb) {
  		fprintf(f, ", thread declared inside InnoDB %lu",
  			(ulong) trx->n_tickets_to_enter_innodb);
  	}
  
  	putc('\n', f);
  
  	if (trx->n_mysql_tables_in_use > 0 || trx->mysql_n_tables_locked > 0) {
  		fprintf(f, "mysql tables in use %lu, locked %lu\n",
  			(ulong) trx->n_mysql_tables_in_use,
  			(ulong) trx->mysql_n_tables_locked);
  	}
  
  	newline = TRUE;
  
  	switch (trx->que_state) {
  	case TRX_QUE_RUNNING:
  		newline = FALSE; break;
  	case TRX_QUE_LOCK_WAIT:
  		fputs("LOCK WAIT ", f); break;
  	case TRX_QUE_ROLLING_BACK:
  		fputs("ROLLING BACK ", f); break;
  	case TRX_QUE_COMMITTING:
  		fputs("COMMITTING ", f); break;
  	default:
  		fprintf(f, "que state %lu ", (ulong) trx->que_state);
  	}
  
  	if (0 < UT_LIST_GET_LEN(trx->trx_locks)
  	    || mem_heap_get_size(trx->lock_heap) > 400) {
  		newline = TRUE;
  
  		fprintf(f, "%lu lock struct(s), heap size %lu,"
  			" %lu row lock(s)",
  			(ulong) UT_LIST_GET_LEN(trx->trx_locks),
  			(ulong) mem_heap_get_size(trx->lock_heap),
  			(ulong) lock_number_of_rows_locked(trx));
  	}
  
  	if (trx->has_search_latch) {
  		newline = TRUE;
  		fputs(", holds adaptive hash latch", f);
  	}
  
  	if (ut_dulint_cmp(trx->undo_no, ut_dulint_zero) != 0) {
  		newline = TRUE;
  		fprintf(f, ", undo log entries %lu",
  			(ulong) ut_dulint_get_low(trx->undo_no));
  	}
  
  	if (newline) {
  		putc('\n', f);
  	}
  
  	if (trx->mysql_thd != NULL) {
  		innobase_mysql_print_thd(f, trx->mysql_thd, max_query_len);
  	}
  }
  
  /***********************************************************************
  Compares the "weight" (or size) of two transactions. The weight of one
  transaction is estimated as the number of altered rows + the number of
  locked rows. Transactions that have edited non-transactional tables are
  considered heavier than ones that have not. */
  
  int
  trx_weight_cmp(
  /*===========*/
  			/* out: <0, 0 or >0; similar to strcmp(3) */
  	trx_t*	a,	/* in: the first transaction to be compared */
  	trx_t*	b)	/* in: the second transaction to be compared */
  {
  	ibool	a_notrans_edit;
  	ibool	b_notrans_edit;
  
  	/* If mysql_thd is NULL for a transaction we assume that it has
  	not edited non-transactional tables. */
  
  	a_notrans_edit = a->mysql_thd != NULL
  	    && thd_has_edited_nontrans_tables(a->mysql_thd);
  
  	b_notrans_edit = b->mysql_thd != NULL
  	    && thd_has_edited_nontrans_tables(b->mysql_thd);
  
  	if (a_notrans_edit && !b_notrans_edit) {
  
  		return(1);
  	}
  
  	if (!a_notrans_edit && b_notrans_edit) {
  
  		return(-1);
  	}
  
  	/* Either both had edited non-transactional tables or both had
  	not, we fall back to comparing the number of altered/locked
  	rows. */
  
  #if 0
  	fprintf(stderr,
  		"%s TRX_WEIGHT(a): %lld+%lu, TRX_WEIGHT(b): %lld+%lu\n",
  		__func__,
  		ut_conv_dulint_to_longlong(a->undo_no),
  		UT_LIST_GET_LEN(a->trx_locks),
  		ut_conv_dulint_to_longlong(b->undo_no),
  		UT_LIST_GET_LEN(b->trx_locks));
  #endif
  
  #define TRX_WEIGHT(t)	\
  	ut_dulint_add((t)->undo_no, UT_LIST_GET_LEN((t)->trx_locks))
  
  	return(ut_dulint_cmp(TRX_WEIGHT(a), TRX_WEIGHT(b)));
  }
  
  /********************************************************************
  Prepares a transaction. */
  
  void
  trx_prepare_off_kernel(
  /*===================*/
  	trx_t*	trx)	/* in: transaction */
  {
  	trx_rseg_t*	rseg;
  	ibool		must_flush_log	= FALSE;
  	dulint		lsn;
  	mtr_t		mtr;
  
  	ut_ad(mutex_own(&kernel_mutex));
  
  	rseg = trx->rseg;
  
  	if (trx->insert_undo != NULL || trx->update_undo != NULL) {
  
  		mutex_exit(&kernel_mutex);
  
  		mtr_start(&mtr);
  
  		must_flush_log = TRUE;
  
  		/* Change the undo log segment states from TRX_UNDO_ACTIVE
  		to TRX_UNDO_PREPARED: these modifications to the file data
  		structure define the transaction as prepared in the
  		file-based world, at the serialization point of lsn. */
  
  		mutex_enter(&(rseg->mutex));
  
  		if (trx->insert_undo != NULL) {
  
  			/* It is not necessary to obtain trx->undo_mutex here
  			because only a single OS thread is allowed to do the
  			transaction prepare for this transaction. */
  
  			trx_undo_set_state_at_prepare(trx, trx->insert_undo,
  						      &mtr);
  		}
  
  		if (trx->update_undo) {
  			trx_undo_set_state_at_prepare(
  				trx, trx->update_undo, &mtr);
  		}
  
  		mutex_exit(&(rseg->mutex));
  
  		/*--------------*/
  		mtr_commit(&mtr);	/* This mtr commit makes the
  					transaction prepared in the file-based
  					world */
  		/*--------------*/
  		lsn = mtr.end_lsn;
  
  		mutex_enter(&kernel_mutex);
  	}
  
  	ut_ad(mutex_own(&kernel_mutex));
  
  	/*--------------------------------------*/
  	trx->conc_state = TRX_PREPARED;
  	trx_n_prepared++;
  	/*--------------------------------------*/
  
  	if (must_flush_log) {
  		/* Depending on the my.cnf options, we may now write the log
  		buffer to the log files, making the prepared state of the
  		transaction durable if the OS does not crash. We may also
  		flush the log files to disk, making the prepared state of the
  		transaction durable also at an OS crash or a power outage.
  
  		The idea in InnoDB's group prepare is that a group of
  		transactions gather behind a trx doing a physical disk write
  		to log files, and when that physical write has been completed,
  		one of those transactions does a write which prepares the whole
  		group. Note that this group prepare will only bring benefit if
  		there are > 2 users in the database. Then at least 2 users can
  		gather behind one doing the physical log write to disk.
  
  		TODO: find out if MySQL holds some mutex when calling this.
  		That would spoil our group prepare algorithm. */
  
  		mutex_exit(&kernel_mutex);
  
  		if (srv_flush_log_at_trx_commit == 0) {
  			/* Do nothing */
  		} else if (srv_flush_log_at_trx_commit == 1) {
  			if (srv_unix_file_flush_method == SRV_UNIX_NOSYNC) {
  				/* Write the log but do not flush it to disk */
  
  				log_write_up_to(lsn, LOG_WAIT_ONE_GROUP,
  						FALSE);
  			} else {
  				/* Write the log to the log files AND flush
  				them to disk */
  
  				log_write_up_to(lsn, LOG_WAIT_ONE_GROUP, TRUE);
  			}
  		} else if (srv_flush_log_at_trx_commit == 2) {
  
  			/* Write the log but do not flush it to disk */
  
  			log_write_up_to(lsn, LOG_WAIT_ONE_GROUP, FALSE);
  		} else {
  			ut_error;
  		}
  
  		mutex_enter(&kernel_mutex);
  	}
  }
  
  /**************************************************************************
  Does the transaction prepare for MySQL. */
  
  ulint
  trx_prepare_for_mysql(
  /*==================*/
  			/* out: 0 or error number */
  	trx_t*	trx)	/* in: trx handle */
  {
  	/* Because we do not do the prepare by sending an Innobase
  	sig to the transaction, we must here make sure that trx has been
  	started. */
  
  	ut_a(trx);
  
  	trx->op_info = "preparing";
  
  	trx_start_if_not_started(trx);
  
  	mutex_enter(&kernel_mutex);
  
  	trx_prepare_off_kernel(trx);
  
  	mutex_exit(&kernel_mutex);
  
  	trx->op_info = "";
  
  	return(0);
  }
  
  /**************************************************************************
  This function is used to find number of prepared transactions and
  their transaction objects for a recovery. */
  
  int
  trx_recover_for_mysql(
  /*==================*/
  				/* out: number of prepared transactions
  				stored in xid_list */
  	XID*	xid_list,	/* in/out: prepared transactions */
  	ulint	len)		/* in: number of slots in xid_list */
  {
  	trx_t*	trx;
  	ulint	count = 0;
  
  	ut_ad(xid_list);
  	ut_ad(len);
  
  	/* We should set those transactions which are in the prepared state
  	to the xid_list */
  
  	mutex_enter(&kernel_mutex);
  
  	trx = UT_LIST_GET_FIRST(trx_sys->trx_list);
  
  	while (trx) {
  		if (trx->conc_state == TRX_PREPARED) {
  			xid_list[count] = trx->xid;
  
  			if (count == 0) {
  				ut_print_timestamp(stderr);
  				fprintf(stderr,
  					"  InnoDB: Starting recovery for"
  					" XA transactions...\n");
  			}
  
  			ut_print_timestamp(stderr);
  			fprintf(stderr,
  				"  InnoDB: Transaction %lu %lu in"
  				" prepared state after recovery\n",
  				(ulong) ut_dulint_get_high(trx->id),
  				(ulong) ut_dulint_get_low(trx->id));
  
  			ut_print_timestamp(stderr);
  			fprintf(stderr,
  				"  InnoDB: Transaction contains changes"
  				" to %lu rows\n",
  				(ulong) ut_conv_dulint_to_longlong(
  					trx->undo_no));
  
  			count++;
  
  			if (count == len) {
  				break;
  			}
  		}
  
  		trx = UT_LIST_GET_NEXT(trx_list, trx);
  	}
  
  	mutex_exit(&kernel_mutex);
  
  	if (count > 0){
  		ut_print_timestamp(stderr);
  		fprintf(stderr,
  			"  InnoDB: %lu transactions in prepared state"
  			" after recovery\n",
  			(ulong) count);
  	}
  
  	return ((int) count);
  }
  
  /***********************************************************************
  This function is used to find one X/Open XA distributed transaction
  which is in the prepared state */
  
  trx_t*
  trx_get_trx_by_xid(
  /*===============*/
  				/* out: trx or NULL;
  				on match, the trx->xid will be invalidated */
  	const XID*	xid)	/* in: X/Open XA transaction identifier */
  {
  	trx_t*	trx;
  
  	if (xid == NULL) {
  
  		return(NULL);
  	}
  
  	mutex_enter(&kernel_mutex);
  
  	trx = UT_LIST_GET_FIRST(trx_sys->trx_list);
  
  	while (trx) {
  		/* Compare two X/Open XA transaction id's: their
  		length should be the same and binary comparison
  		of gtrid_lenght+bqual_length bytes should be
  		the same */
  
  		if (trx->conc_state == TRX_PREPARED
  		    && xid->gtrid_length == trx->xid.gtrid_length
  		    && xid->bqual_length == trx->xid.bqual_length
  		    && memcmp(xid->data, trx->xid.data,
  			      xid->gtrid_length + xid->bqual_length) == 0) {
  
  			/* Invalidate the XID, so that subsequent calls
  			will not find it. */
  			memset(&trx->xid, 0, sizeof(trx->xid));
  			trx->xid.formatID = -1;
  			break;
  		}
  
  		trx = UT_LIST_GET_NEXT(trx_list, trx);
  	}
  
  	mutex_exit(&kernel_mutex);
  
  	return(trx);
  }
  