btr0pcur.c

这是linux下运行的mysql软件包,可用于linux 下安装 php + mysql + apach 的网络配置

/******************************************************
The index tree persistent cursor

(c) 1996 Innobase Oy

Created 2/23/1996 Heikki Tuuri
*******************************************************/

#include "btr0pcur.h"

#ifdef UNIV_NONINL
#include "btr0pcur.ic"
#endif

#include "ut0byte.h"
#include "rem0cmp.h"
#include "trx0trx.h"

/******************************************************************
Allocates memory for a persistent cursor object and initializes the cursor. */

btr_pcur_t*
btr_pcur_create_for_mysql(void)
/*============================*/
				/* out, own: persistent cursor */
{
	btr_pcur_t*	pcur;

	pcur = mem_alloc(sizeof(btr_pcur_t));

	pcur->btr_cur.index = NULL;
	btr_pcur_init(pcur);
	
	return(pcur);
}

/******************************************************************
Frees the memory for a persistent cursor object. */

void
btr_pcur_free_for_mysql(
/*====================*/
	btr_pcur_t*	cursor)	/* in, own: persistent cursor */
{
	if (cursor->old_rec_buf != NULL) {

		mem_free(cursor->old_rec_buf);

		cursor->old_rec_buf = NULL;
	}

	cursor->btr_cur.page_cur.rec = NULL;
	cursor->old_rec = NULL;
	cursor->old_n_fields = 0;
	cursor->old_stored = BTR_PCUR_OLD_NOT_STORED;
	
	cursor->latch_mode = BTR_NO_LATCHES;
	cursor->pos_state = BTR_PCUR_NOT_POSITIONED;

	mem_free(cursor);
}

/******************************************************************
The position of the cursor is stored by taking an initial segment of the
record the cursor is positioned on, before, or after, and copying it to the
cursor data structure, or just setting a flag if the cursor id before the
first in an EMPTY tree, or after the last in an EMPTY tree. NOTE that the
page where the cursor is positioned must not be empty if the index tree is
not totally empty! */

void
btr_pcur_store_position(
/*====================*/
	btr_pcur_t*	cursor, /* in: persistent cursor */
	mtr_t*		mtr)	/* in: mtr */
{
	page_cur_t*	page_cursor;
	rec_t*		rec;
	dict_tree_t*	tree;
	page_t*		page;
	ulint		offs;
	
	ut_a(cursor->pos_state == BTR_PCUR_IS_POSITIONED);
	ut_ad(cursor->latch_mode != BTR_NO_LATCHES);

	tree = btr_cur_get_tree(btr_pcur_get_btr_cur(cursor));

	page_cursor = btr_pcur_get_page_cur(cursor);

	rec = page_cur_get_rec(page_cursor);
	page = ut_align_down(rec, UNIV_PAGE_SIZE);
	offs = ut_align_offset(rec, UNIV_PAGE_SIZE);

	ut_ad(mtr_memo_contains(mtr, buf_block_align(page),
							MTR_MEMO_PAGE_S_FIX)
	      || mtr_memo_contains(mtr, buf_block_align(page),
							MTR_MEMO_PAGE_X_FIX));
	ut_a(cursor->latch_mode != BTR_NO_LATCHES);

	if (UNIV_UNLIKELY(page_get_n_recs(page) == 0)) {
		/* It must be an empty index tree; NOTE that in this case
		we do not store the modify_clock, but always do a search
		if we restore the cursor position */

		ut_a(btr_page_get_next(page, mtr) == FIL_NULL);
		ut_a(btr_page_get_prev(page, mtr) == FIL_NULL);

		cursor->old_stored = BTR_PCUR_OLD_STORED;

		if (page_rec_is_supremum_low(offs)) {

			cursor->rel_pos = BTR_PCUR_AFTER_LAST_IN_TREE;
		} else {
			cursor->rel_pos = BTR_PCUR_BEFORE_FIRST_IN_TREE;
		}

		return;
	} 

	if (page_rec_is_supremum_low(offs)) {

		rec = page_rec_get_prev(rec);

		cursor->rel_pos = BTR_PCUR_AFTER;

	} else if (page_rec_is_infimum_low(offs)) {

		rec = page_rec_get_next(rec);

		cursor->rel_pos = BTR_PCUR_BEFORE;
	} else {
		cursor->rel_pos = BTR_PCUR_ON;
	}

	cursor->old_stored = BTR_PCUR_OLD_STORED;
	cursor->old_rec = dict_tree_copy_rec_order_prefix(tree, rec,
						&cursor->old_n_fields,
						&cursor->old_rec_buf,
						&cursor->buf_size);

	cursor->block_when_stored = buf_block_align(page);	
	cursor->modify_clock = buf_block_get_modify_clock(
				cursor->block_when_stored);
}

/******************************************************************
Copies the stored position of a pcur to another pcur. */

void
btr_pcur_copy_stored_position(
/*==========================*/
	btr_pcur_t*	pcur_receive,	/* in: pcur which will receive the
					position info */
	btr_pcur_t*	pcur_donate)	/* in: pcur from which the info is
					copied */
{
	if (pcur_receive->old_rec_buf) {
		mem_free(pcur_receive->old_rec_buf);
	}

	ut_memcpy((byte*)pcur_receive, (byte*)pcur_donate, sizeof(btr_pcur_t));

	if (pcur_donate->old_rec_buf) {

		pcur_receive->old_rec_buf = mem_alloc(pcur_donate->buf_size);
	
		ut_memcpy(pcur_receive->old_rec_buf, pcur_donate->old_rec_buf,
						pcur_donate->buf_size);
		pcur_receive->old_rec = pcur_receive->old_rec_buf
			+ (pcur_donate->old_rec - pcur_donate->old_rec_buf);
	}	

	pcur_receive->old_n_fields = pcur_donate->old_n_fields;
}

/******************************************************************
Restores the stored position of a persistent cursor bufferfixing the page and
obtaining the specified latches. If the cursor position was saved when the
(1) cursor was positioned on a user record: this function restores the position
to the last record LESS OR EQUAL to the stored record;
(2) cursor was positioned on a page infimum record: restores the position to
the last record LESS than the user record which was the successor of the page
infimum;
(3) cursor was positioned on the page supremum: restores to the first record
GREATER than the user record which was the predecessor of the supremum.
(4) cursor was positioned before the first or after the last in an empty tree:
restores to before first or after the last in the tree. */

ibool
btr_pcur_restore_position(
/*======================*/
					/* out: TRUE if the cursor position
					was stored when it was on a user record
					and it can be restored on a user record
					whose ordering fields are identical to
					the ones of the original user record */
	ulint		latch_mode,	/* in: BTR_SEARCH_LEAF, ... */
	btr_pcur_t*	cursor, 	/* in: detached persistent cursor */
	mtr_t*		mtr)		/* in: mtr */
{
	dict_tree_t*	tree;
	page_t*		page;
	dtuple_t*	tuple;
	ulint		mode;
	ulint		old_mode;
	mem_heap_t*	heap;

	if (UNIV_UNLIKELY(cursor->old_stored != BTR_PCUR_OLD_STORED)
	    || UNIV_UNLIKELY(cursor->pos_state != BTR_PCUR_WAS_POSITIONED
			     && cursor->pos_state != BTR_PCUR_IS_POSITIONED)) {
		ut_print_buf(stderr, (const byte*)cursor, sizeof(btr_pcur_t));
		if (cursor->trx_if_known) {
			trx_print(stderr, cursor->trx_if_known, 0);
		}
		
		ut_error;
	}

	if (UNIV_UNLIKELY(cursor->rel_pos == BTR_PCUR_AFTER_LAST_IN_TREE
			|| cursor->rel_pos == BTR_PCUR_BEFORE_FIRST_IN_TREE)) {

	    	/* In these cases we do not try an optimistic restoration,
	    	but always do a search */

		btr_cur_open_at_index_side(
			cursor->rel_pos == BTR_PCUR_BEFORE_FIRST_IN_TREE,
			btr_pcur_get_btr_cur(cursor)->index, latch_mode,
					btr_pcur_get_btr_cur(cursor), mtr);

		cursor->block_when_stored =
				buf_block_align(btr_pcur_get_page(cursor));

		return(FALSE);
	}
	
	ut_a(cursor->old_rec);
	ut_a(cursor->old_n_fields);

	page = btr_cur_get_page(btr_pcur_get_btr_cur(cursor));

	if (UNIV_LIKELY(latch_mode == BTR_SEARCH_LEAF)
			|| UNIV_LIKELY(latch_mode == BTR_MODIFY_LEAF)) {
		/* Try optimistic restoration */
	    
		if (UNIV_LIKELY(buf_page_optimistic_get(latch_mode,
					    cursor->block_when_stored, page,
					    cursor->modify_clock, mtr))) {
			cursor->pos_state = BTR_PCUR_IS_POSITIONED;
#ifdef UNIV_SYNC_DEBUG
			buf_page_dbg_add_level(page, SYNC_TREE_NODE);
#endif /* UNIV_SYNC_DEBUG */
			if (cursor->rel_pos == BTR_PCUR_ON) {
#ifdef UNIV_DEBUG
				rec_t*		rec;
				ulint*		offsets1;
				ulint*		offsets2;
				dict_index_t*	index;
#endif /* UNIV_DEBUG */
				cursor->latch_mode = latch_mode;
#ifdef UNIV_DEBUG
				rec = btr_pcur_get_rec(cursor);
				index = dict_tree_find_index(
					btr_cur_get_tree(
						btr_pcur_get_btr_cur(cursor)),
					rec);

				heap = mem_heap_create(256);
				offsets1 = rec_get_offsets(cursor->old_rec,
						index, NULL,
						cursor->old_n_fields, &heap);
				offsets2 = rec_get_offsets(rec, index, NULL,
						cursor->old_n_fields, &heap);

				ut_ad(cmp_rec_rec(cursor->old_rec,
					rec, offsets1, offsets2, index) == 0);
				mem_heap_free(heap);
#endif /* UNIV_DEBUG */
				return(TRUE);
			}

			return(FALSE);
		}
	}