~drizzle-trunk/drizzle/development

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

Row undo

(c) 1997 Innobase Oy

Created 1/8/1997 Heikki Tuuri

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

#ifndef row0undo_h

#define row0undo_h

#include "univ.i"

#include "mtr0mtr.h"

#include "trx0sys.h"

#include "btr0types.h"

#include "btr0pcur.h"

#include "dict0types.h"

#include "trx0types.h"

#include "que0types.h"

#include "row0types.h"

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

Creates a row undo node to a query graph. */

UNIV_INTERN

undo_node_t*

row_undo_node_create(

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

				/* out, own: undo node */

	trx_t*		trx,	/* in: transaction */

	que_thr_t*	parent,	/* in: parent node, i.e., a thr node */

	mem_heap_t*	heap);	/* in: memory heap where created */

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

Looks for the clustered index record when node has the row reference.

The pcur in node is used in the search. If found, stores the row to node,

and stores the position of pcur, and detaches it. The pcur must be closed

by the caller in any case. */

UNIV_INTERN

ibool

row_undo_search_clust_to_pcur(

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

				/* out: TRUE if found; NOTE the node->pcur

				must be closed by the caller, regardless of

				the return value */

	undo_node_t*	node);	/* in: row undo node */

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

Undoes a row operation in a table. This is a high-level function used

in SQL execution graphs. */

UNIV_INTERN

que_thr_t*

row_undo_step(

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

				/* out: query thread to run next or NULL */

	que_thr_t*	thr);	/* in: query thread */

/* A single query thread will try to perform the undo for all successive

versions of a clustered index record, if the transaction has modified it

several times during the execution which is rolled back. It may happen

that the task is transferred to another query thread, if the other thread

is assigned to handle an undo log record in the chain of different versions

of the record, and the other thread happens to get the x-latch to the

clustered index record at the right time.

	If a query thread notices that the clustered index record it is looking

for is missing, or the roll ptr field in the record doed not point to the

undo log record the thread was assigned to handle, then it gives up the undo

task for that undo log record, and fetches the next. This situation can occur

just in the case where the transaction modified the same record several times

and another thread is currently doing the undo for successive versions of

that index record. */

/* Undo node structure */

struct undo_node_struct{

	que_common_t	common;	/* node type: QUE_NODE_UNDO */

	ulint		state;	/* node execution state */

	trx_t*		trx;	/* trx for which undo is done */

	dulint		roll_ptr;/* roll pointer to undo log record */

	trx_undo_rec_t*	undo_rec;/* undo log record */

	dulint		undo_no;/* undo number of the record */

	ulint		rec_type;/* undo log record type: TRX_UNDO_INSERT_REC,

				... */

	dulint		new_roll_ptr; /* roll ptr to restore to clustered index

				record */

	dulint		new_trx_id; /* trx id to restore to clustered index

				record */

	btr_pcur_t	pcur;	/* persistent cursor used in searching the

				clustered index record */

	dict_table_t*	table;	/* table where undo is done */

	ulint		cmpl_info;/* compiler analysis of an update */

	upd_t*		update;	/* update vector for a clustered index

				record */

	dtuple_t*	ref;	/* row reference to the next row to handle */

	dtuple_t*	row;	/* a copy (also fields copied to heap) of the

				row to handle */

	row_ext_t*	ext;	/* NULL, or prefixes of the externally

				stored columns of the row */

	dtuple_t*	undo_row;/* NULL, or the row after undo */

	row_ext_t*	undo_ext;/* NULL, or prefixes of the externally

				stored columns of undo_row */

	dict_index_t*	index;	/* the next index whose record should be

				handled */

	mem_heap_t*	heap;	/* memory heap used as auxiliary storage for

				row; this must be emptied after undo is tried

				on a row */

};

/* Execution states for an undo node */

#define	UNDO_NODE_FETCH_NEXT	1	/* we should fetch the next undo log

					record */

#define	UNDO_NODE_PREV_VERS	2	/* the roll ptr to previous version of

					a row is stored in node, and undo

					should be done based on it */

#define UNDO_NODE_INSERT	3

#define UNDO_NODE_MODIFY	4

#ifndef UNIV_NONINL

#include "row0undo.ic"

#endif

#endif