~drizzle-trunk/drizzle/development

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

Cursor read

(c) 1997 Innobase Oy

Created 2/16/1997 Heikki Tuuri

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

#ifndef read0read_h

#define read0read_h

#include "univ.i"

#include "ut0byte.h"

#include "ut0lst.h"

#include "trx0trx.h"

#include "read0types.h"

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

Opens a read view where exactly the transactions serialized before this

point in time are seen in the view. */

read_view_t*

read_view_open_now(

/*===============*/

					/* out, own: read view struct */

	dulint		cr_trx_id,	/* in: trx_id of creating

					transaction, or (0, 0) used in

					purge */

	mem_heap_t*	heap);		/* in: memory heap from which

					allocated */

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

Makes a copy of the oldest existing read view, or opens a new. The view

must be closed with ..._close. */

read_view_t*

read_view_oldest_copy_or_open_new(

/*==============================*/

					/* out, own: read view struct */

	dulint		cr_trx_id,	/* in: trx_id of creating

					transaction, or (0, 0) used in

					purge */

	mem_heap_t*	heap);		/* in: memory heap from which

					allocated */

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

Closes a read view. */

void

read_view_close(

/*============*/

	read_view_t*	view);	/* in: read view */

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

Closes a consistent read view for MySQL. This function is called at an SQL

statement end if the trx isolation level is <= TRX_ISO_READ_COMMITTED. */

void

read_view_close_for_mysql(

/*======================*/

	trx_t*	trx);	/* in: trx which has a read view */

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

Checks if a read view sees the specified transaction. */

UNIV_INLINE

ibool

read_view_sees_trx_id(

/*==================*/

				/* out: TRUE if sees */

	read_view_t*	view,	/* in: read view */

	dulint		trx_id);/* in: trx id */

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

Prints a read view to stderr. */

void

read_view_print(

/*============*/

	read_view_t*	view);	/* in: read view */

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

Create a consistent cursor view for mysql to be used in cursors. In this

consistent read view modifications done by the creating transaction or future

transactions are not visible. */

cursor_view_t*

read_cursor_view_create_for_mysql(

/*==============================*/

	trx_t*		cr_trx);/* in: trx where cursor view is created */

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

Close a given consistent cursor view for mysql and restore global read view

back to a transaction read view. */

void

read_cursor_view_close_for_mysql(

/*=============================*/

	trx_t*		trx,		/* in: trx */

	cursor_view_t*	curview);	/* in: cursor view to be closed */

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

This function sets a given consistent cursor view to a transaction

read view if given consistent cursor view is not NULL. Otherwise, function

restores a global read view to a transaction read view. */

void

read_cursor_set_for_mysql(

/*======================*/

	trx_t*		trx,	/* in: transaction where cursor is set */

	cursor_view_t*	curview);/* in: consistent cursor view to be set */

/* Read view lists the trx ids of those transactions for which a consistent

read should not see the modifications to the database. */

struct read_view_struct{

	ulint	type;		/* VIEW_NORMAL, VIEW_HIGH_GRANULARITY */

	dulint	undo_no;	/* (0, 0) or if type is VIEW_HIGH_GRANULARITY

				transaction undo_no when this high-granularity

				consistent read view was created */

	ibool	can_be_too_old;	/* TRUE if the system has had to purge old

				versions which this read view should be able

				to access: the read view can bump into the

				DB_MISSING_HISTORY error */

	dulint	low_limit_no;	/* The view does not need to see the undo

				logs for transactions whose transaction number

				is strictly smaller (<) than this value: they

				can be removed in purge if not needed by other

				views */

	dulint	low_limit_id;	/* The read should not see any transaction

				with trx id >= this value */

	dulint	up_limit_id;	/* The read should see all trx ids which

				are strictly smaller (<) than this value */

	ulint	n_trx_ids;	/* Number of cells in the trx_ids array */

	dulint*	trx_ids;	/* Additional trx ids which the read should

				not see: typically, these are the active

				transactions at the time when the read is

				serialized, except the reading transaction

				itself; the trx ids in this array are in a

				descending order */

	dulint	creator_trx_id;	/* trx id of creating transaction, or

				(0, 0) used in purge */

	UT_LIST_NODE_T(read_view_t) view_list;

				/* List of read views in trx_sys */

};

/* Read view types */

#define VIEW_NORMAL		1	/* Normal consistent read view

					where transaction does not see changes

					made by active transactions except

					creating transaction. */

#define VIEW_HIGH_GRANULARITY	2	/* High-granularity read view where

					transaction does not see changes

					made by active transactions and own

					changes after a point in time when this

					read view was created. */

/* Implement InnoDB framework to support consistent read views in

cursors. This struct holds both heap where consistent read view

is allocated and pointer to a read view. */

struct cursor_view_struct{

	mem_heap_t*	heap;

				/* Memory heap for the cursor view */

	read_view_t*	read_view;

				/* Consistent read view of the cursor*/

	ulint		n_mysql_tables_in_use;

				/* number of Innobase tables used in the

				processing of this cursor */

};

#ifndef UNIV_NONINL

#include "read0read.ic"

#endif

#endif