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/******************************************************
The index tree cursor
(c) 1994-1996 Innobase Oy
Created 10/16/1994 Heikki Tuuri
*******************************************************/
#include "btr0btr.h"
/*************************************************************
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 */
btr_cur_t* cursor) /* in: tree cursor */
{
return(&(cursor->page_cur));
}
/*************************************************************
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)));
}
/*************************************************************
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(buf_frame_align(page_cur_get_rec(&(cursor->page_cur))));
}
/*************************************************************
Returns the tree of a cursor. */
UNIV_INLINE
dict_tree_t*
btr_cur_get_tree(
/*=============*/
/* out: tree */
btr_cur_t* cursor) /* in: tree cursor */
{
return((cursor->index)->tree);
}
/*************************************************************
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 */
btr_cur_t* cursor) /* in: cursor */
{
page_cur_position(rec, 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, buf_block_align(
btr_cur_get_page(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. */
if (dict_tree_get_page((cursor->index)->tree)
== buf_frame_get_page_no(page)) {
/* It is the root page */
return(FALSE);
}
return(TRUE);
}
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 */
mtr_t* mtr) /* in: mtr */
{
ulint rec_size;
page_t* page;
ut_ad(mtr_memo_contains(mtr, buf_block_align(
btr_cur_get_page(cursor)),
MTR_MEMO_PAGE_X_FIX));
rec_size = rec_get_size(btr_cur_get_rec(cursor));
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. */
if (dict_tree_get_page((cursor->index)->tree)
== buf_frame_get_page_no(page)) {
/* It is the root page */
return(TRUE);
}
return(FALSE);
}
return(TRUE);
}
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