~drizzle-trunk/drizzle/development

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

Copyright (c) 1997, 2009, 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 row/row0vers.c

Row versions

Created 2/6/1997 Heikki Tuuri

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

#include "row0vers.h"

#ifdef UNIV_NONINL

#include "row0vers.ic"

#endif

#include "dict0dict.h"

#include "dict0boot.h"

#include "btr0btr.h"

#include "mach0data.h"

#include "trx0rseg.h"

#include "trx0trx.h"

#include "trx0roll.h"

#include "trx0undo.h"

#include "trx0purge.h"

#include "trx0rec.h"

#include "que0que.h"

#include "row0row.h"

#include "row0upd.h"

#include "rem0cmp.h"

#include "read0read.h"

#include "lock0lock.h"

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

Finds out if an active transaction has inserted or modified a secondary

index record. NOTE: the kernel mutex is temporarily released in this

function!

@return NULL if committed, else the active transaction */

UNIV_INTERN

trx_t*

row_vers_impl_x_locked_off_kernel(

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

	const rec_t*	rec,	/*!< in: record in a secondary index */

	dict_index_t*	index,	/*!< in: the secondary index */

	const ulint*	offsets)/*!< in: rec_get_offsets(rec, index) */

{

	dict_index_t*	clust_index;

	rec_t*		clust_rec;

	ulint*		clust_offsets;

	rec_t*		version;

	trx_id_t	trx_id;

	mem_heap_t*	heap;

	mem_heap_t*	heap2;

	dtuple_t*	row;

	dtuple_t*	entry	= NULL; /* assignment to eliminate compiler

					warning */

	trx_t*		trx;

	ulint		rec_del;

	ulint		err;

	mtr_t		mtr;

	ulint		comp;

	ut_ad(mutex_own(&kernel_mutex));

#ifdef UNIV_SYNC_DEBUG

	ut_ad(!rw_lock_own(&(purge_sys->latch), RW_LOCK_SHARED));

#endif /* UNIV_SYNC_DEBUG */

	mutex_exit(&kernel_mutex);

	mtr_start(&mtr);

	/* Search for the clustered index record: this is a time-consuming

	operation: therefore we release the kernel mutex; also, the release

	is required by the latching order convention. The latch on the

	clustered index locks the top of the stack of versions. We also

	reserve purge_latch to lock the bottom of the version stack. */

	clust_rec = row_get_clust_rec(BTR_SEARCH_LEAF, rec, index,

				      &clust_index, &mtr);

	if (!clust_rec) {

		/* In a rare case it is possible that no clust rec is found

		for a secondary index record: if in row0umod.c

		row_undo_mod_remove_clust_low() we have already removed the

		clust rec, while purge is still cleaning and removing

		secondary index records associated with earlier versions of

		the clustered index record. In that case there cannot be

		any implicit lock on the secondary index record, because

		an active transaction which has modified the secondary index

		record has also modified the clustered index record. And in

		a rollback we always undo the modifications to secondary index

		records before the clustered index record. */

		mutex_enter(&kernel_mutex);

		mtr_commit(&mtr);

		return(NULL);

	}

	heap = mem_heap_create(1024);

	clust_offsets = rec_get_offsets(clust_rec, clust_index, NULL,

					ULINT_UNDEFINED, &heap);

	trx_id = row_get_rec_trx_id(clust_rec, clust_index, clust_offsets);

	mtr_s_lock(&(purge_sys->latch), &mtr);

	mutex_enter(&kernel_mutex);

	trx = NULL;

	if (!trx_is_active(trx_id)) {

		/* The transaction that modified or inserted clust_rec is no

		longer active: no implicit lock on rec */

		goto exit_func;

	}

	if (!lock_check_trx_id_sanity(trx_id, clust_rec, clust_index,

				      clust_offsets, TRUE)) {

		/* Corruption noticed: try to avoid a crash by returning */

		goto exit_func;

	}

	comp = page_rec_is_comp(rec);

	ut_ad(index->table == clust_index->table);

	ut_ad(!!comp == dict_table_is_comp(index->table));

	ut_ad(!comp == !page_rec_is_comp(clust_rec));

	/* We look up if some earlier version, which was modified by the trx_id

	transaction, of the clustered index record would require rec to be in

	a different state (delete marked or unmarked, or have different field

	values, or not existing). If there is such a version, then rec was

	modified by the trx_id transaction, and it has an implicit x-lock on

	rec. Note that if clust_rec itself would require rec to be in a

	different state, then the trx_id transaction has not yet had time to

	modify rec, and does not necessarily have an implicit x-lock on rec. */

	rec_del = rec_get_deleted_flag(rec, comp);

	trx = NULL;

	version = clust_rec;

	for (;;) {

		rec_t*		prev_version;

		ulint		vers_del;

		row_ext_t*	ext;

		trx_id_t	prev_trx_id;

		mutex_exit(&kernel_mutex);

		/* While we retrieve an earlier version of clust_rec, we

		release the kernel mutex, because it may take time to access

		the disk. After the release, we have to check if the trx_id

		transaction is still active. We keep the semaphore in mtr on

		the clust_rec page, so that no other transaction can update

		it and get an implicit x-lock on rec. */

		heap2 = heap;

		heap = mem_heap_create(1024);

		err = trx_undo_prev_version_build(clust_rec, &mtr, version,

						  clust_index, clust_offsets,

						  heap, &prev_version);

		mem_heap_free(heap2); /* free version and clust_offsets */

		if (prev_version == NULL) {

			mutex_enter(&kernel_mutex);

			if (!trx_is_active(trx_id)) {

				/* Transaction no longer active: no

				implicit x-lock */

				break;

			}

			/* If the transaction is still active,

			clust_rec must be a fresh insert, because no

			previous version was found. */

			ut_ad(err == DB_SUCCESS);

			/* It was a freshly inserted version: there is an

			implicit x-lock on rec */

			trx = trx_get_on_id(trx_id);

			break;

		}

		clust_offsets = rec_get_offsets(prev_version, clust_index,

						NULL, ULINT_UNDEFINED, &heap);

		vers_del = rec_get_deleted_flag(prev_version, comp);

		prev_trx_id = row_get_rec_trx_id(prev_version, clust_index,

						 clust_offsets);

		/* If the trx_id and prev_trx_id are different and if

		the prev_version is marked deleted then the

		prev_trx_id must have already committed for the trx_id

		to be able to modify the row. Therefore, prev_trx_id

		cannot hold any implicit lock. */

		if (vers_del && trx_id != prev_trx_id) {

			mutex_enter(&kernel_mutex);

			break;

		}

		/* The stack of versions is locked by mtr.  Thus, it

		is safe to fetch the prefixes for externally stored

		columns. */

		row = row_build(ROW_COPY_POINTERS, clust_index, prev_version,

				clust_offsets, NULL, &ext, heap);

		entry = row_build_index_entry(row, ext, index, heap);

		/* entry may be NULL if a record was inserted in place

		of a deleted record, and the BLOB pointers of the new

		record were not initialized yet.  But in that case,

		prev_version should be NULL. */

		ut_a(entry);

		mutex_enter(&kernel_mutex);

		if (!trx_is_active(trx_id)) {

			/* Transaction no longer active: no implicit x-lock */

			break;

		}

		/* If we get here, we know that the trx_id transaction is

		still active and it has modified prev_version. Let us check

		if prev_version would require rec to be in a different

		state. */

		/* The previous version of clust_rec must be

		accessible, because the transaction is still active

		and clust_rec was not a fresh insert. */

		ut_ad(err == DB_SUCCESS);

		/* We check if entry and rec are identified in the alphabetical

		ordering */

		if (0 == cmp_dtuple_rec(entry, rec, offsets)) {

			/* The delete marks of rec and prev_version should be

			equal for rec to be in the state required by

			prev_version */

			if (rec_del != vers_del) {

				trx = trx_get_on_id(trx_id);

				break;

			}

			/* It is possible that the row was updated so that the

			secondary index record remained the same in

			alphabetical ordering, but the field values changed

			still. For example, 'abc' -> 'ABC'. Check also that. */

			dtuple_set_types_binary(entry,

						dtuple_get_n_fields(entry));

			if (0 != cmp_dtuple_rec(entry, rec, offsets)) {

				trx = trx_get_on_id(trx_id);

				break;

			}

		} else if (!rec_del) {

			/* The delete mark should be set in rec for it to be

			in the state required by prev_version */

			trx = trx_get_on_id(trx_id);

			break;

		}

		if (trx_id != prev_trx_id) {

			/* The versions modified by the trx_id transaction end

			to prev_version: no implicit x-lock */

			break;

		}

		version = prev_version;

	}/* for (;;) */

exit_func:

	mtr_commit(&mtr);

	mem_heap_free(heap);

	return(trx);

}

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

Finds out if we must preserve a delete marked earlier version of a clustered

index record, because it is >= the purge view.

@return	TRUE if earlier version should be preserved */

UNIV_INTERN

ibool

row_vers_must_preserve_del_marked(

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

	trx_id_t	trx_id,	/*!< in: transaction id in the version */

	mtr_t*		mtr)	/*!< in: mtr holding the latch on the

				clustered index record; it will also

				hold the latch on purge_view */

{

#ifdef UNIV_SYNC_DEBUG

	ut_ad(!rw_lock_own(&(purge_sys->latch), RW_LOCK_SHARED));

#endif /* UNIV_SYNC_DEBUG */

	mtr_s_lock(&(purge_sys->latch), mtr);

	if (trx_purge_update_undo_must_exist(trx_id)) {

		/* A purge operation is not yet allowed to remove this

		delete marked record */

		return(TRUE);

	}

	return(FALSE);

}

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

Finds out if a version of the record, where the version >= the current

purge view, should have ientry as its secondary index entry. We check

if there is any not delete marked version of the record where the trx

id >= purge view, and the secondary index entry and ientry are identified in

the alphabetical ordering; exactly in this case we return TRUE.

@return	TRUE if earlier version should have */

UNIV_INTERN

ibool

row_vers_old_has_index_entry(

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

	ibool		also_curr,/*!< in: TRUE if also rec is included in the

				versions to search; otherwise only versions

				prior to it are searched */

	const rec_t*	rec,	/*!< in: record in the clustered index; the

				caller must have a latch on the page */

	mtr_t*		mtr,	/*!< in: mtr holding the latch on rec; it will

				also hold the latch on purge_view */

	dict_index_t*	index,	/*!< in: the secondary index */

	const dtuple_t*	ientry)	/*!< in: the secondary index entry */

{

	const rec_t*	version;

	rec_t*		prev_version;

	dict_index_t*	clust_index;

	ulint*		clust_offsets;

	mem_heap_t*	heap;

	mem_heap_t*	heap2;

	const dtuple_t*	row;

	const dtuple_t*	entry;

	ulint		err;

	ulint		comp;

	ut_ad(mtr_memo_contains_page(mtr, rec, MTR_MEMO_PAGE_X_FIX)

	      || mtr_memo_contains_page(mtr, rec, MTR_MEMO_PAGE_S_FIX));

#ifdef UNIV_SYNC_DEBUG

	ut_ad(!rw_lock_own(&(purge_sys->latch), RW_LOCK_SHARED));

#endif /* UNIV_SYNC_DEBUG */

	mtr_s_lock(&(purge_sys->latch), mtr);

	clust_index = dict_table_get_first_index(index->table);

	comp = page_rec_is_comp(rec);

	ut_ad(!dict_table_is_comp(index->table) == !comp);

	heap = mem_heap_create(1024);

	clust_offsets = rec_get_offsets(rec, clust_index, NULL,

					ULINT_UNDEFINED, &heap);

	if (also_curr && !rec_get_deleted_flag(rec, comp)) {

		row_ext_t*	ext;

		/* The stack of versions is locked by mtr.

		Thus, it is safe to fetch the prefixes for

		externally stored columns. */

		row = row_build(ROW_COPY_POINTERS, clust_index,

				rec, clust_offsets, NULL, &ext, heap);

		entry = row_build_index_entry(row, ext, index, heap);

		/* If entry == NULL, the record contains unset BLOB

		pointers.  This must be a freshly inserted record.  If

		this is called from

		row_purge_remove_sec_if_poss_low(), the thread will

		hold latches on the clustered index and the secondary

		index.  Because the insert works in three steps:

			(1) insert the record to clustered index

			(2) store the BLOBs and update BLOB pointers

			(3) insert records to secondary indexes

		the purge thread can safely ignore freshly inserted

		records and delete the secondary index record.  The

		thread that inserted the new record will be inserting

		the secondary index records. */

		/* NOTE that we cannot do the comparison as binary

		fields because the row is maybe being modified so that

		the clustered index record has already been updated to

		a different binary value in a char field, but the

		collation identifies the old and new value anyway! */

		if (entry && !dtuple_coll_cmp(ientry, entry)) {

			mem_heap_free(heap);

			return(TRUE);

		}

	}

	version = rec;

	for (;;) {

		heap2 = heap;

		heap = mem_heap_create(1024);

		err = trx_undo_prev_version_build(rec, mtr, version,

						  clust_index, clust_offsets,

						  heap, &prev_version);

		mem_heap_free(heap2); /* free version and clust_offsets */

		if (err != DB_SUCCESS || !prev_version) {

			/* Versions end here */

			mem_heap_free(heap);

			return(FALSE);

		}

		clust_offsets = rec_get_offsets(prev_version, clust_index,

						NULL, ULINT_UNDEFINED, &heap);

		if (!rec_get_deleted_flag(prev_version, comp)) {

			row_ext_t*	ext;

			/* The stack of versions is locked by mtr.

			Thus, it is safe to fetch the prefixes for

			externally stored columns. */

			row = row_build(ROW_COPY_POINTERS, clust_index,

					prev_version, clust_offsets,

					NULL, &ext, heap);

			entry = row_build_index_entry(row, ext, index, heap);

			/* If entry == NULL, the record contains unset

			BLOB pointers.  This must be a freshly

			inserted record that we can safely ignore.

			For the justification, see the comments after

			the previous row_build_index_entry() call. */

			/* NOTE that we cannot do the comparison as binary

			fields because maybe the secondary index record has

			already been updated to a different binary value in

			a char field, but the collation identifies the old

			and new value anyway! */

			if (entry && !dtuple_coll_cmp(ientry, entry)) {

				mem_heap_free(heap);

				return(TRUE);

			}

		}

		version = prev_version;

	}

}

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

Constructs the version of a clustered index record which a consistent

read should see. We assume that the trx id stored in rec is such that

the consistent read should not see rec in its present version.

@return	DB_SUCCESS or DB_MISSING_HISTORY */

UNIV_INTERN

ulint

row_vers_build_for_consistent_read(

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

	const rec_t*	rec,	/*!< in: record in a clustered index; the

				caller must have a latch on the page; this

				latch locks the top of the stack of versions

				of this records */

	mtr_t*		mtr,	/*!< in: mtr holding the latch on rec */

	dict_index_t*	index,	/*!< in: the clustered index */

	ulint**		offsets,/*!< in/out: offsets returned by

				rec_get_offsets(rec, index) */

	read_view_t*	view,	/*!< in: the consistent read view */

	mem_heap_t**	offset_heap,/*!< in/out: memory heap from which

				the offsets are allocated */

	mem_heap_t*	in_heap,/*!< in: memory heap from which the memory for

				*old_vers is allocated; memory for possible

				intermediate versions is allocated and freed

				locally within the function */

	rec_t**		old_vers)/*!< out, own: old version, or NULL if the

				record does not exist in the view, that is,

				it was freshly inserted afterwards */

{

	const rec_t*	version;

	rec_t*		prev_version;

	trx_id_t	trx_id;

	mem_heap_t*	heap		= NULL;

	byte*		buf;

	ulint		err;

	ut_ad(dict_index_is_clust(index));

	ut_ad(mtr_memo_contains_page(mtr, rec, MTR_MEMO_PAGE_X_FIX)

	      || mtr_memo_contains_page(mtr, rec, MTR_MEMO_PAGE_S_FIX));

#ifdef UNIV_SYNC_DEBUG

	ut_ad(!rw_lock_own(&(purge_sys->latch), RW_LOCK_SHARED));

#endif /* UNIV_SYNC_DEBUG */

	ut_ad(rec_offs_validate(rec, index, *offsets));

	trx_id = row_get_rec_trx_id(rec, index, *offsets);

	ut_ad(!read_view_sees_trx_id(view, trx_id));

	rw_lock_s_lock(&(purge_sys->latch));

	version = rec;

	for (;;) {

		mem_heap_t*	heap2	= heap;

		trx_undo_rec_t* undo_rec;

		roll_ptr_t	roll_ptr;

		undo_no_t	undo_no;

		heap = mem_heap_create(1024);

		/* If we have high-granularity consistent read view and

		creating transaction of the view is the same as trx_id in

		the record we see this record only in the case when

		undo_no of the record is < undo_no in the view. */

		if (view->type == VIEW_HIGH_GRANULARITY

		    && view->creator_trx_id == trx_id) {

			roll_ptr = row_get_rec_roll_ptr(version, index,

							*offsets);

			undo_rec = trx_undo_get_undo_rec_low(roll_ptr, heap);

			undo_no = trx_undo_rec_get_undo_no(undo_rec);

			mem_heap_empty(heap);

			if (view->undo_no > undo_no) {

				/* The view already sees this version: we can

				copy it to in_heap and return */

				buf = mem_heap_alloc(in_heap,

						     rec_offs_size(*offsets));

				*old_vers = rec_copy(buf, version, *offsets);

				rec_offs_make_valid(*old_vers, index,

						    *offsets);

				err = DB_SUCCESS;

				break;

			}

		}

		err = trx_undo_prev_version_build(rec, mtr, version, index,

						  *offsets, heap,

						  &prev_version);

		if (heap2) {

			mem_heap_free(heap2); /* free version */

		}

		if (err != DB_SUCCESS) {

			break;

		}

		if (prev_version == NULL) {

			/* It was a freshly inserted version */

			*old_vers = NULL;

			err = DB_SUCCESS;

			break;

		}

		*offsets = rec_get_offsets(prev_version, index, *offsets,

					   ULINT_UNDEFINED, offset_heap);

		trx_id = row_get_rec_trx_id(prev_version, index, *offsets);

		if (read_view_sees_trx_id(view, trx_id)) {

			/* The view already sees this version: we can copy

			it to in_heap and return */

			buf = mem_heap_alloc(in_heap, rec_offs_size(*offsets));

			*old_vers = rec_copy(buf, prev_version, *offsets);

			rec_offs_make_valid(*old_vers, index, *offsets);

			err = DB_SUCCESS;

			break;

		}

		version = prev_version;

	}/* for (;;) */

	mem_heap_free(heap);

	rw_lock_s_unlock(&(purge_sys->latch));

	return(err);

}

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

Constructs the last committed version of a clustered index record,

which should be seen by a semi-consistent read.

@return	DB_SUCCESS or DB_MISSING_HISTORY */

UNIV_INTERN

ulint

row_vers_build_for_semi_consistent_read(

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

	const rec_t*	rec,	/*!< in: record in a clustered index; the

				caller must have a latch on the page; this

				latch locks the top of the stack of versions

				of this records */

	mtr_t*		mtr,	/*!< in: mtr holding the latch on rec */

	dict_index_t*	index,	/*!< in: the clustered index */

	ulint**		offsets,/*!< in/out: offsets returned by

				rec_get_offsets(rec, index) */

	mem_heap_t**	offset_heap,/*!< in/out: memory heap from which

				the offsets are allocated */

	mem_heap_t*	in_heap,/*!< in: memory heap from which the memory for

				*old_vers is allocated; memory for possible

				intermediate versions is allocated and freed

				locally within the function */

	const rec_t**	old_vers)/*!< out: rec, old version, or NULL if the

				record does not exist in the view, that is,

				it was freshly inserted afterwards */

{

	const rec_t*	version;

	mem_heap_t*	heap		= NULL;

	byte*		buf;

	ulint		err;

	trx_id_t	rec_trx_id	= 0;

	ut_ad(dict_index_is_clust(index));

	ut_ad(mtr_memo_contains_page(mtr, rec, MTR_MEMO_PAGE_X_FIX)

	      || mtr_memo_contains_page(mtr, rec, MTR_MEMO_PAGE_S_FIX));

#ifdef UNIV_SYNC_DEBUG

	ut_ad(!rw_lock_own(&(purge_sys->latch), RW_LOCK_SHARED));

#endif /* UNIV_SYNC_DEBUG */

	ut_ad(rec_offs_validate(rec, index, *offsets));

	rw_lock_s_lock(&(purge_sys->latch));

	/* The S-latch on purge_sys prevents the purge view from

	changing.  Thus, if we have an uncommitted transaction at

	this point, then purge cannot remove its undo log even if

	the transaction could commit now. */

	version = rec;

	for (;;) {

		trx_t*		version_trx;

		mem_heap_t*	heap2;

		rec_t*		prev_version;

		trx_id_t	version_trx_id;

		version_trx_id = row_get_rec_trx_id(version, index, *offsets);

		if (rec == version) {

			rec_trx_id = version_trx_id;

		}

		mutex_enter(&kernel_mutex);

		version_trx = trx_get_on_id(version_trx_id);

		mutex_exit(&kernel_mutex);

		if (!version_trx

		    || version_trx->conc_state == TRX_NOT_STARTED

		    || version_trx->conc_state == TRX_COMMITTED_IN_MEMORY) {

			/* We found a version that belongs to a

			committed transaction: return it. */

			if (rec == version) {

				*old_vers = rec;

				err = DB_SUCCESS;

				break;

			}

			/* We assume that a rolled-back transaction stays in

			TRX_ACTIVE state until all the changes have been

			rolled back and the transaction is removed from

			the global list of transactions. */

			if (rec_trx_id == version_trx_id) {

				/* The transaction was committed while

				we searched for earlier versions.

				Return the current version as a

				semi-consistent read. */

				version = rec;

				*offsets = rec_get_offsets(version,

							   index, *offsets,

							   ULINT_UNDEFINED,

							   offset_heap);

			}

			buf = mem_heap_alloc(in_heap, rec_offs_size(*offsets));

			*old_vers = rec_copy(buf, version, *offsets);

			rec_offs_make_valid(*old_vers, index, *offsets);

			err = DB_SUCCESS;

			break;

		}

		heap2 = heap;

		heap = mem_heap_create(1024);

		err = trx_undo_prev_version_build(rec, mtr, version, index,

						  *offsets, heap,

						  &prev_version);

		if (heap2) {

			mem_heap_free(heap2); /* free version */

		}

		if (UNIV_UNLIKELY(err != DB_SUCCESS)) {

			break;

		}

		if (prev_version == NULL) {

			/* It was a freshly inserted version */

			*old_vers = NULL;

			err = DB_SUCCESS;

			break;

		}

		version = prev_version;

		*offsets = rec_get_offsets(version, index, *offsets,

					   ULINT_UNDEFINED, offset_heap);

	}/* for (;;) */

	if (heap) {

		mem_heap_free(heap);

	}

	rw_lock_s_unlock(&(purge_sys->latch));

	return(err);

}