path: root/storage/innobase/include/btr0pcur.h

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

/**************************************************//**
@file include/btr0pcur.h
The index tree persistent cursor

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

#ifndef btr0pcur_h
#define btr0pcur_h

#include "dict0dict.h"
#include "btr0cur.h"
#include "buf0block_hint.h"
#include "btr0btr.h"
#include "gis0rtree.h"

/* Relative positions for a stored cursor position */
enum btr_pcur_pos_t {
	BTR_PCUR_ON		= 1,
	BTR_PCUR_BEFORE		= 2,
	BTR_PCUR_AFTER		= 3,
/* Note that if the tree is not empty, btr_pcur_store_position does not
use the following, but only uses the above three alternatives, where the
position is stored relative to a specific record: this makes implementation
of a scroll cursor easier */
	BTR_PCUR_BEFORE_FIRST_IN_TREE	= 4,	/* in an empty tree */
	BTR_PCUR_AFTER_LAST_IN_TREE	= 5	/* in an empty tree */
};

/**************************************************************//**
Allocates memory for a persistent cursor object and initializes the cursor.
@return own: persistent cursor */
btr_pcur_t*
btr_pcur_create_for_mysql(void);
/*============================*/

/**************************************************************//**
Resets a persistent cursor object, freeing ::old_rec_buf if it is
allocated and resetting the other members to their initial values. */
void
btr_pcur_reset(
/*===========*/
	btr_pcur_t*	cursor);/*!< in, out: persistent cursor */

/**************************************************************//**
Frees the memory for a persistent cursor object. */
void
btr_pcur_free_for_mysql(
/*====================*/
	btr_pcur_t*	cursor);	/*!< in, own: persistent cursor */
/**************************************************************//**
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 */
/**************************************************************//**
Sets the old_rec_buf field to NULL. */
UNIV_INLINE
void
btr_pcur_init(
/*==========*/
	btr_pcur_t*	pcur);	/*!< in: persistent cursor */

/** Free old_rec_buf.
@param[in]	pcur	Persistent cursor holding old_rec to be freed. */
UNIV_INLINE
void
btr_pcur_free(
	btr_pcur_t*	pcur);

/**************************************************************//**
Initializes and opens a persistent cursor to an index tree. It should be
closed with btr_pcur_close. */
UNIV_INLINE
dberr_t
btr_pcur_open_low(
/*==============*/
	dict_index_t*	index,	/*!< in: index */
	ulint		level,	/*!< in: level in the btree */
	const dtuple_t*	tuple,	/*!< in: tuple on which search done */
	page_cur_mode_t	mode,	/*!< in: PAGE_CUR_L, ...;
				NOTE that if the search is made using a unique
				prefix of a record, mode should be
				PAGE_CUR_LE, not PAGE_CUR_GE, as the latter
				may end up on the previous page from the
				record! */
	ulint		latch_mode,/*!< in: BTR_SEARCH_LEAF, ... */
	btr_pcur_t*	cursor, /*!< in: memory buffer for persistent cursor */
	ib_uint64_t	autoinc,/*!< in: PAGE_ROOT_AUTO_INC to be written
				(0 if none) */
	mtr_t*		mtr);	/*!< in: mtr */
#define btr_pcur_open(i,t,md,l,c,m)				\
	btr_pcur_open_low(i,0,t,md,l,c,0,m)
/**************************************************************//**
Opens an persistent cursor to an index tree without initializing the
cursor. */
UNIV_INLINE
dberr_t
btr_pcur_open_with_no_init_func(
/*============================*/
	dict_index_t*	index,	/*!< in: index */
	const dtuple_t*	tuple,	/*!< in: tuple on which search done */
	page_cur_mode_t	mode,	/*!< in: PAGE_CUR_L, ...;
				NOTE that if the search is made using a unique
				prefix of a record, mode should be
				PAGE_CUR_LE, not PAGE_CUR_GE, as the latter
				may end up on the previous page of the
				record! */
	ulint		latch_mode,/*!< in: BTR_SEARCH_LEAF, ...;
				NOTE that if ahi_latch then we might not
				acquire a cursor page latch, but assume
				that the ahi_latch protects the record! */
	btr_pcur_t*	cursor, /*!< in: memory buffer for persistent cursor */
#ifdef BTR_CUR_HASH_ADAPT
	srw_spin_lock*	ahi_latch,
				/*!< in: currently held AHI rdlock, or NULL */
#endif /* BTR_CUR_HASH_ADAPT */
	mtr_t*		mtr);	/*!< in: mtr */
#ifdef BTR_CUR_HASH_ADAPT
# define btr_pcur_open_with_no_init(ix,t,md,l,cur,ahi,m)		\
	btr_pcur_open_with_no_init_func(ix,t,md,l,cur,ahi,m)
#else /* BTR_CUR_HASH_ADAPT */
# define btr_pcur_open_with_no_init(ix,t,md,l,cur,ahi,m)		\
	btr_pcur_open_with_no_init_func(ix,t,md,l,cur,m)
#endif /* BTR_CUR_HASH_ADAPT */

/*****************************************************************//**
Opens a persistent cursor at either end of an index. */
UNIV_INLINE
dberr_t
btr_pcur_open_at_index_side(
/*========================*/
	bool		from_left,	/*!< in: true if open to the low end,
					false if to the high end */
	dict_index_t*	index,		/*!< in: index */
	ulint		latch_mode,	/*!< in: latch mode */
	btr_pcur_t*	pcur,		/*!< in/out: cursor */
	bool		init_pcur,	/*!< in: whether to initialize pcur */
	ulint		level,		/*!< in: level to search for
					(0=leaf) */
	mtr_t*		mtr)		/*!< in/out: mini-transaction */
	MY_ATTRIBUTE((nonnull));
/**************************************************************//**
Gets the up_match value for a pcur after a search.
@return number of matched fields at the cursor or to the right if
search mode was PAGE_CUR_GE, otherwise undefined */
UNIV_INLINE
ulint
btr_pcur_get_up_match(
/*==================*/
	const btr_pcur_t*	cursor); /*!< in: persistent cursor */
/**************************************************************//**
Gets the low_match value for a pcur after a search.
@return number of matched fields at the cursor or to the right if
search mode was PAGE_CUR_LE, otherwise undefined */
UNIV_INLINE
ulint
btr_pcur_get_low_match(
/*===================*/
	const btr_pcur_t*	cursor); /*!< in: persistent cursor */
/**************************************************************//**
If mode is PAGE_CUR_G or PAGE_CUR_GE, opens a persistent cursor on the first
user record satisfying the search condition, in the case PAGE_CUR_L or
PAGE_CUR_LE, on the last user record. If no such user record exists, then
in the first case sets the cursor after last in tree, and in the latter case
before first in tree. The latching mode must be BTR_SEARCH_LEAF or
BTR_MODIFY_LEAF. */
void
btr_pcur_open_on_user_rec(
	dict_index_t*	index,		/*!< in: index */
	const dtuple_t*	tuple,		/*!< in: tuple on which search done */
	page_cur_mode_t	mode,		/*!< in: PAGE_CUR_L, ... */
	ulint		latch_mode,	/*!< in: BTR_SEARCH_LEAF or
					BTR_MODIFY_LEAF */
	btr_pcur_t*	cursor,		/*!< in: memory buffer for persistent
					cursor */
	mtr_t*		mtr);		/*!< in: mtr */
/**********************************************************************//**
Positions a cursor at a randomly chosen position within a B-tree.
@return true if the index is available and we have put the cursor, false
if the index is unavailable */
UNIV_INLINE
bool
btr_pcur_open_at_rnd_pos(
	dict_index_t*	index,		/*!< in: index */
	ulint		latch_mode,	/*!< in: BTR_SEARCH_LEAF, ... */
	btr_pcur_t*	cursor,		/*!< in/out: B-tree pcur */
	mtr_t*		mtr);		/*!< in: mtr */
/**************************************************************//**
Frees the possible memory heap of a persistent cursor and sets the latch
mode of the persistent cursor to BTR_NO_LATCHES.
WARNING: this function does not release the latch on the page where the
cursor is currently positioned. The latch is acquired by the
"move to next/previous" family of functions. Since recursive shared locks
are not allowed, you must take care (if using the cursor in S-mode) to
manually release the latch by either calling
btr_leaf_page_release(btr_pcur_get_block(&pcur), pcur.latch_mode, mtr)
or by committing the mini-transaction right after btr_pcur_close().
A subsequent attempt to crawl the same page in the same mtr would cause
an assertion failure. */
UNIV_INLINE
void
btr_pcur_close(
/*===========*/
	btr_pcur_t*	cursor);	/*!< in: persistent 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 */
/*********************************************************//**
Gets the rel_pos field for a cursor whose position has been stored.
@return BTR_PCUR_ON, ... */
UNIV_INLINE
ulint
btr_pcur_get_rel_pos(
/*=================*/
	const btr_pcur_t*	cursor);/*!< in: persistent cursor */
/**************************************************************//**
Commits the mtr and sets the pcur latch mode to BTR_NO_LATCHES,
that is, the cursor becomes detached.
Function btr_pcur_store_position should be used before calling this,
if restoration of cursor is wanted later. */
UNIV_INLINE
void
btr_pcur_commit_specify_mtr(
/*========================*/
	btr_pcur_t*	pcur,	/*!< in: persistent cursor */
	mtr_t*		mtr);	/*!< in: mtr to commit */

/** Commits the mtr and sets the clustered index pcur and secondary index
pcur latch mode to BTR_NO_LATCHES, that is, the cursor becomes detached.
Function btr_pcur_store_position should be used for both cursor before
calling this, if restoration of cursor is wanted later.
@param[in]	pcur		persistent cursor
@param[in]	sec_pcur	secondary index persistent cursor
@param[in]	mtr		mtr to commit */
UNIV_INLINE
void
btr_pcurs_commit_specify_mtr(
	btr_pcur_t*	pcur,
	btr_pcur_t*	sec_pcur,
	mtr_t*		mtr);

/*********************************************************//**
Moves the persistent cursor to the next record in the tree. If no records are
left, the cursor stays 'after last in tree'.
@return TRUE if the cursor was not after last in tree */
UNIV_INLINE
ibool
btr_pcur_move_to_next(
/*==================*/
	btr_pcur_t*	cursor,	/*!< in: persistent cursor; NOTE that the
				function may release the page latch */
	mtr_t*		mtr);	/*!< in: mtr */
/*********************************************************//**
Moves the persistent cursor to the previous record in the tree. If no records
are left, the cursor stays 'before first in tree'.
@return TRUE if the cursor was not before first in tree */
ibool
btr_pcur_move_to_prev(
/*==================*/
	btr_pcur_t*	cursor,	/*!< in: persistent cursor; NOTE that the
				function may release the page latch */
	mtr_t*		mtr);	/*!< in: mtr */
/*********************************************************//**
Moves the persistent cursor to the next user record in the tree. If no user
records are left, the cursor ends up 'after last in tree'.
@return TRUE if the cursor moved forward, ending on a user record */
UNIV_INLINE
ibool
btr_pcur_move_to_next_user_rec(
/*===========================*/
	btr_pcur_t*	cursor,	/*!< in: persistent cursor; NOTE that the
				function may release the page latch */
	mtr_t*		mtr);	/*!< in: mtr */
/*********************************************************//**
Moves the persistent cursor to the first record on the next page.
Releases the latch on the current page, and bufferunfixes it.
Note that there must not be modifications on the current page,
as then the x-latch can be released only in mtr_commit. */
void
btr_pcur_move_to_next_page(
/*=======================*/
	btr_pcur_t*	cursor,	/*!< in: persistent cursor; must be on the
				last record of the current page */
	mtr_t*		mtr);	/*!< in: mtr */

#define btr_pcur_get_btr_cur(cursor) (&(cursor)->btr_cur)
#define btr_pcur_get_page_cur(cursor) (&(cursor)->btr_cur.page_cur)
#define btr_pcur_get_page(cursor) btr_pcur_get_block(cursor)->page.frame

/*********************************************************//**
Checks if the persistent cursor is on a user record. */
UNIV_INLINE
ibool
btr_pcur_is_on_user_rec(
/*====================*/
	const btr_pcur_t*	cursor);/*!< in: persistent cursor */
/*********************************************************//**
Checks if the persistent cursor is after the last user record on
a page. */
UNIV_INLINE
ibool
btr_pcur_is_after_last_on_page(
/*===========================*/
	const btr_pcur_t*	cursor);/*!< in: persistent cursor */
/*********************************************************//**
Checks if the persistent cursor is before the first user record on
a page. */
UNIV_INLINE
ibool
btr_pcur_is_before_first_on_page(
/*=============================*/
	const btr_pcur_t*	cursor);/*!< in: persistent cursor */
/*********************************************************//**
Checks if the persistent cursor is before the first user record in
the index tree. */
static inline bool btr_pcur_is_before_first_in_tree(btr_pcur_t* cursor);
/*********************************************************//**
Checks if the persistent cursor is after the last user record in
the index tree. */
static inline bool btr_pcur_is_after_last_in_tree(btr_pcur_t* cursor);
/*********************************************************//**
Moves the persistent cursor to the next record on the same page. */
UNIV_INLINE
void
btr_pcur_move_to_next_on_page(
/*==========================*/
	btr_pcur_t*	cursor);/*!< in/out: persistent cursor */
/*********************************************************//**
Moves the persistent cursor to the previous record on the same page. */
UNIV_INLINE
void
btr_pcur_move_to_prev_on_page(
/*==========================*/
	btr_pcur_t*	cursor);/*!< in/out: persistent cursor */
/*********************************************************//**
Moves the persistent cursor to the infimum record on the same page. */
UNIV_INLINE
void
btr_pcur_move_before_first_on_page(
/*===============================*/
	btr_pcur_t*	cursor); /*!< in/out: persistent cursor */

/** Position state of persistent B-tree cursor. */
enum pcur_pos_t {
	/** The persistent cursor is not positioned. */
	BTR_PCUR_NOT_POSITIONED = 0,
	/** The persistent cursor was previously positioned.
	TODO: currently, the state can be BTR_PCUR_IS_POSITIONED,
	though it really should be BTR_PCUR_WAS_POSITIONED,
	because we have no obligation to commit the cursor with
	mtr; similarly latch_mode may be out of date. This can
	lead to problems if btr_pcur is not used the right way;
	all current code should be ok. */
	BTR_PCUR_WAS_POSITIONED,
	/** The persistent cursor is positioned by optimistic get to the same
	record as it was positioned at. Not used for rel_pos == BTR_PCUR_ON.
	It may need adjustment depending on previous/current search direction
	and rel_pos. */
	BTR_PCUR_IS_POSITIONED_OPTIMISTIC,
	/** The persistent cursor is positioned by index search.
	Or optimistic get for rel_pos == BTR_PCUR_ON. */
	BTR_PCUR_IS_POSITIONED
};

/* The persistent B-tree cursor structure. This is used mainly for SQL
selects, updates, and deletes. */

struct btr_pcur_t{
	/** Return value of restore_position() */
	enum restore_status {
		/** cursor position on user rec and points on the record with
		the same field values as in the stored record */
		SAME_ALL,
		/** cursor position is on user rec and points on the record with
		the same unique field values as in the stored record */
		SAME_UNIQ,
		/** cursor position is not on user rec or points on the record
		with not the same uniq field values as in the stored record */
		NOT_SAME
	};
	/** a B-tree cursor */
	btr_cur_t	btr_cur;
	/** see TODO note below!
	BTR_SEARCH_LEAF, BTR_MODIFY_LEAF, BTR_MODIFY_TREE or BTR_NO_LATCHES,
	depending on the latching state of the page and tree where the cursor
	is positioned; BTR_NO_LATCHES means that the cursor is not currently
	positioned:
	we say then that the cursor is detached; it can be restored to
	attached if the old position was stored in old_rec */
	ulint		latch_mode;
	/** true if old_rec is stored */
	bool		old_stored;
	/** if cursor position is stored, contains an initial segment of the
	latest record cursor was positioned either on, before or after */
	rec_t*		old_rec;
	/** btr_cur.index->n_core_fields when old_rec was copied */
	uint16		old_n_core_fields;
	/** number of fields in old_rec */
	uint16		old_n_fields;
	/** BTR_PCUR_ON, BTR_PCUR_BEFORE, or BTR_PCUR_AFTER, depending on
	whether cursor was on, before, or after the old_rec record */
	enum btr_pcur_pos_t	rel_pos;
	/** buffer block when the position was stored */
	buf::Block_hint		block_when_stored;
	/** the modify clock value of the buffer block when the cursor position
	was stored */
	ib_uint64_t	modify_clock;
	/** btr_pcur_store_position() and btr_pcur_restore_position() state. */
	enum pcur_pos_t	pos_state;
	/** PAGE_CUR_G, ... */
	page_cur_mode_t	search_mode;
	/** the transaction, if we know it; otherwise this field is not defined;
	can ONLY BE USED in error prints in fatal assertion failures! */
	trx_t*		trx_if_known;
	/*-----------------------------*/
	/* NOTE that the following fields may possess dynamically allocated
	memory which should be freed if not needed anymore! */

	/** NULL, or a dynamically allocated buffer for old_rec */
	byte*		old_rec_buf;
	/** old_rec_buf size if old_rec_buf is not NULL */
	ulint		buf_size;

	btr_pcur_t() :
		btr_cur(), latch_mode(RW_NO_LATCH),
		old_stored(false), old_rec(NULL),
		old_n_fields(0), rel_pos(btr_pcur_pos_t(0)),
		block_when_stored(),
		modify_clock(0), pos_state(BTR_PCUR_NOT_POSITIONED),
		search_mode(PAGE_CUR_UNSUPP), trx_if_known(NULL),
		old_rec_buf(NULL), buf_size(0)
	{
		btr_cur.init();
	}

	/** Return the index of this persistent cursor */
	dict_index_t*	index() const { return(btr_cur.index); }
	/** 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.
	@param restore_latch_mode BTR_SEARCH_LEAF, ...
	@param mtr mtr
	@return btr_pcur_t::SAME_ALL cursor position on user rec and points on
	the record with the same field values as in the stored record,
	btr_pcur_t::SAME_UNIQ cursor position is on user rec and points on the
	record with the same unique field values as in the stored record,
	btr_pcur_t::NOT_SAME cursor position is not on user rec or points on
	the record with not the samebuniq field values as in the stored */
	restore_status restore_position(ulint latch_mode, mtr_t *mtr);
};

inline buf_block_t *btr_pcur_get_block(btr_pcur_t *cursor)
{
  ut_ad(cursor->pos_state == BTR_PCUR_IS_POSITIONED);
  return cursor->btr_cur.page_cur.block;
}

inline const buf_block_t *btr_pcur_get_block(const btr_pcur_t *cursor)
{
  ut_ad(cursor->pos_state == BTR_PCUR_IS_POSITIONED);
  return cursor->btr_cur.page_cur.block;
}

inline rec_t *btr_pcur_get_rec(const btr_pcur_t *cursor)
{
  ut_ad(cursor->pos_state == BTR_PCUR_IS_POSITIONED);
  ut_ad(cursor->latch_mode != BTR_NO_LATCHES);
  return cursor->btr_cur.page_cur.rec;
}

#include "btr0pcur.inl"

#endif