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

Copyright (c) 1994, 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., 59 Temple
Place, Suite 330, Boston, MA 02111-1307 USA

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

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

Created 10/16/1994 Heikki Tuuri
*******************************************************/

#include "btr0btr.h"

#ifdef UNIV_DEBUG
/*************************************************************
Returns the page cursor component of a tree cursor. */
UNIV_INLINE
page_cur_t*
btr_cur_get_page_cur(
/*=================*/
					/* out: pointer to page cursor
					component */
	const btr_cur_t*	cursor)	/* in: tree cursor */
{
	return(&((btr_cur_t*) cursor)->page_cur);
}
#endif /* UNIV_DEBUG */
/*************************************************************
Returns the buffer block on which the tree cursor is positioned. */
UNIV_INLINE
buf_block_t*
btr_cur_get_block(
/*==============*/
				/* out: pointer to buffer block */
	btr_cur_t*	cursor)	/* in: tree cursor */
{
	return(page_cur_get_block(btr_cur_get_page_cur(cursor)));
}

/*************************************************************
Returns the record pointer of a tree cursor. */
UNIV_INLINE
rec_t*
btr_cur_get_rec(
/*============*/
				/* out: pointer to record */
	btr_cur_t*	cursor)	/* in: tree cursor */
{
	return(page_cur_get_rec(&(cursor->page_cur)));
}

/*************************************************************
Returns the compressed page on which the tree cursor is positioned. */
UNIV_INLINE
page_zip_des_t*
btr_cur_get_page_zip(
/*=================*/
				/* out: pointer to compressed page,
				or NULL if the page is not compressed */
	btr_cur_t*	cursor)	/* in: tree cursor */
{
	return(buf_block_get_page_zip(btr_cur_get_block(cursor)));
}

/*************************************************************
Invalidates a tree cursor by setting record pointer to NULL. */
UNIV_INLINE
void
btr_cur_invalidate(
/*===============*/
	btr_cur_t*	cursor)	/* in: tree cursor */
{
	page_cur_invalidate(&(cursor->page_cur));
}

/*************************************************************
Returns the page of a tree cursor. */
UNIV_INLINE
page_t*
btr_cur_get_page(
/*=============*/
				/* out: pointer to page */
	btr_cur_t*	cursor)	/* in: tree cursor */
{
	return(page_align(page_cur_get_rec(&(cursor->page_cur))));
}

/*************************************************************
Returns the index of a cursor. */
UNIV_INLINE
dict_index_t*
btr_cur_get_index(
/*==============*/
				/* out: index */
	btr_cur_t*	cursor)	/* in: B-tree cursor */
{
	return(cursor->index);
}

/*************************************************************
Positions a tree cursor at a given record. */
UNIV_INLINE
void
btr_cur_position(
/*=============*/
	dict_index_t*	index,	/* in: index */
	rec_t*		rec,	/* in: record in tree */
	buf_block_t*	block,	/* in: buffer block of rec */
	btr_cur_t*	cursor)	/* out: cursor */
{
	ut_ad(page_align(rec) == block->frame);

	page_cur_position(rec, block, btr_cur_get_page_cur(cursor));

	cursor->index = index;
}

/*************************************************************************
Checks if compressing an index page where a btr cursor is placed makes
sense. */
UNIV_INLINE
ibool
btr_cur_compress_recommendation(
/*============================*/
				/* out: TRUE if compression is recommended */
	btr_cur_t*	cursor,	/* in: btr cursor */
	mtr_t*		mtr)	/* in: mtr */
{
	page_t*		page;

	ut_ad(mtr_memo_contains(mtr, btr_cur_get_block(cursor),
				MTR_MEMO_PAGE_X_FIX));

	page = btr_cur_get_page(cursor);

	if ((page_get_data_size(page) < BTR_CUR_PAGE_COMPRESS_LIMIT)
	    || ((btr_page_get_next(page, mtr) == FIL_NULL)
		&& (btr_page_get_prev(page, mtr) == FIL_NULL))) {

		/* The page fillfactor has dropped below a predefined
		minimum value OR the level in the B-tree contains just
		one page: we recommend compression if this is not the
		root page. */

		return(dict_index_get_page(cursor->index)
		       != page_get_page_no(page));
	}

	return(FALSE);
}

/*************************************************************************
Checks if the record on which the cursor is placed can be deleted without
making tree compression necessary (or, recommended). */
UNIV_INLINE
ibool
btr_cur_can_delete_without_compress(
/*================================*/
				/* out: TRUE if can be deleted without
				recommended compression */
	btr_cur_t*	cursor,	/* in: btr cursor */
	ulint		rec_size,/* in: rec_get_size(btr_cur_get_rec(cursor))*/
	mtr_t*		mtr)	/* in: mtr */
{
	page_t*		page;

	ut_ad(mtr_memo_contains(mtr, btr_cur_get_block(cursor),
				MTR_MEMO_PAGE_X_FIX));

	page = btr_cur_get_page(cursor);

	if ((page_get_data_size(page) - rec_size < BTR_CUR_PAGE_COMPRESS_LIMIT)
	    || ((btr_page_get_next(page, mtr) == FIL_NULL)
		&& (btr_page_get_prev(page, mtr) == FIL_NULL))
	    || (page_get_n_recs(page) < 2)) {

		/* The page fillfactor will drop below a predefined
		minimum value, OR the level in the B-tree contains just
		one page, OR the page will become empty: we recommend
		compression if this is not the root page. */

		return(dict_index_get_page(cursor->index)
		       == page_get_page_no(page));
	}

	return(TRUE);
}