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

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

/********************************************************************//**
@file include/btr0sea.h
The index tree adaptive search

Created 2/17/1996 Heikki Tuuri
*************************************************************************/

#ifndef btr0sea_h
#define btr0sea_h

#include "univ.i"

#include "rem0rec.h"
#include "dict0dict.h"
#include "btr0types.h"
#include "mtr0mtr.h"
#include "ha0ha.h"

/** Creates and initializes the adaptive search system at a database start.
@param[in]	hash_size	hash table size. */
void
btr_search_sys_create(ulint hash_size);

/** Resize hash index hash table.
@param[in]	hash_size	hash index hash table size */
void
btr_search_sys_resize(ulint hash_size);

/** Frees the adaptive search system at a database shutdown. */
void
btr_search_sys_free();

/** Disable the adaptive hash search system and empty the index.
@param  need_mutex      need to acquire dict_sys->mutex */
void
btr_search_disable(
	bool	need_mutex);
/** Enable the adaptive hash search system. */
void
btr_search_enable();

/********************************************************************//**
Returns search info for an index.
@return search info; search mutex reserved */
UNIV_INLINE
btr_search_t*
btr_search_get_info(
/*================*/
	dict_index_t*	index)	/*!< in: index */
	MY_ATTRIBUTE((nonnull));

/** Creates and initializes a search info struct.
@param[in]	heap		heap where created.
@return own: search info struct */
btr_search_t*
btr_search_info_create(mem_heap_t* heap);

/** Returns the value of ref_count. The value is protected by latch.
@param[in]	info		search info
@param[in]	index		index identifier
@return ref_count value. */
ulint
btr_search_info_get_ref_count(
	btr_search_t*	info,
	dict_index_t*	index);

/*********************************************************************//**
Updates the search info. */
UNIV_INLINE
void
btr_search_info_update(
/*===================*/
	dict_index_t*	index,	/*!< in: index of the cursor */
	btr_cur_t*	cursor);/*!< in: cursor which was just positioned */

/** Tries to guess the right search position based on the hash search info
of the index. Note that if mode is PAGE_CUR_LE, which is used in inserts,
and the function returns TRUE, then cursor->up_match and cursor->low_match
both have sensible values.
@param[in,out]	index		index
@param[in,out]	info		index search info
@param[in]	tuple		logical record
@param[in]	mode		PAGE_CUR_L, ....
@param[in]	latch_mode	BTR_SEARCH_LEAF, ...;
				NOTE that only if has_search_latch is 0, we will
				have a latch set on the cursor page, otherwise
				we assume the caller uses his search latch
				to protect the record!
@param[out]	cursor		tree cursor
@param[in]	has_search_latch
				latch mode the caller currently has on
				search system: RW_S/X_LATCH or 0
@param[in]	mtr		mini transaction
@return TRUE if succeeded */
ibool
btr_search_guess_on_hash(
	dict_index_t*	index,
	btr_search_t*	info,
	const dtuple_t*	tuple,
	ulint		mode,
	ulint		latch_mode,
	btr_cur_t*	cursor,
	ulint		has_search_latch,
	mtr_t*		mtr);

/** Moves or deletes hash entries for moved records. If new_page is already
hashed, then the hash index for page, if any, is dropped. If new_page is not
hashed, and page is hashed, then a new hash index is built to new_page with the
same parameters as page (this often happens when a page is split).
@param[in,out]	new_block	records are copied to this page.
@param[in,out]	block		index page from which record are copied, and the
				copied records will be deleted from this page.
@param[in,out]	index		record descriptor */
void
btr_search_move_or_delete_hash_entries(
	buf_block_t*	new_block,
	buf_block_t*	block,
	dict_index_t*	index);

/** Drop any adaptive hash index entries that point to an index page.
@param[in,out]	block	block containing index page, s- or x-latched, or an
			index page for which we know that
			block->buf_fix_count == 0 or it is an index page which
			has already been removed from the buf_pool->page_hash
			i.e.: it is in state BUF_BLOCK_REMOVE_HASH */
void
btr_search_drop_page_hash_index(buf_block_t* block);

/** Drop any adaptive hash index entries that may point to an index
page that may be in the buffer pool, when a page is evicted from the
buffer pool or freed in a file segment.
@param[in]	page_id		page id
@param[in]	page_size	page size */
void
btr_search_drop_page_hash_when_freed(
	const page_id_t&	page_id,
	const page_size_t&	page_size);

/** Updates the page hash index when a single record is inserted on a page.
@param[in]	cursor	cursor which was positioned to the place to insert
			using btr_cur_search_, and the new record has been
			inserted next to the cursor. */
void
btr_search_update_hash_node_on_insert(btr_cur_t* cursor);

/** Updates the page hash index when a single record is inserted on a page.
@param[in]	cursor		cursor which was positioned to the
				place to insert using btr_cur_search_...,
				and the new record has been inserted next
				to the cursor */
void
btr_search_update_hash_on_insert(btr_cur_t* cursor);

/** Updates the page hash index when a single record is deleted from a page.
@param[in]	cursor	cursor which was positioned on the record to delete
			using btr_cur_search_, the record is not yet deleted.*/
void
btr_search_update_hash_on_delete(btr_cur_t* cursor);

/** Validates the search system.
@return true if ok */
bool
btr_search_validate();

/** X-Lock the search latch (corresponding to given index)
@param[in]	index	index handler */
UNIV_INLINE
void
btr_search_x_lock(const dict_index_t* index);

/** X-Unlock the search latch (corresponding to given index)
@param[in]	index	index handler */
UNIV_INLINE
void
btr_search_x_unlock(const dict_index_t* index);

/** Lock all search latches in exclusive mode. */
UNIV_INLINE
void
btr_search_x_lock_all();

/** Unlock all search latches from exclusive mode. */
UNIV_INLINE
void
btr_search_x_unlock_all();

/** S-Lock the search latch (corresponding to given index)
@param[in]	index	index handler */
UNIV_INLINE
void
btr_search_s_lock(const dict_index_t* index);

/** S-Unlock the search latch (corresponding to given index)
@param[in]	index	index handler */
UNIV_INLINE
void
btr_search_s_unlock(const dict_index_t* index);

/** Lock all search latches in shared mode. */
UNIV_INLINE
void
btr_search_s_lock_all();

#ifdef UNIV_DEBUG
/** Check if thread owns all the search latches.
@param[in]	mode	lock mode check
@retval true if owns all of them
@retval false if does not own some of them */
UNIV_INLINE
bool
btr_search_own_all(ulint mode);

/** Check if thread owns any of the search latches.
@param[in]	mode	lock mode check
@retval true if owns any of them
@retval false if owns no search latch */
UNIV_INLINE
bool
btr_search_own_any(ulint mode);
#endif /* UNIV_DEBUG */

/** Unlock all search latches from shared mode. */
UNIV_INLINE
void
btr_search_s_unlock_all();

/** Get the latch based on index attributes.
A latch is selected from an array of latches using pair of index-id, space-id.
@param[in]	index	index handler
@return latch */
UNIV_INLINE
rw_lock_t*
btr_get_search_latch(const dict_index_t* index);

/** Get the hash-table based on index attributes.
A table is selected from an array of tables using pair of index-id, space-id.
@param[in]	index	index handler
@return hash table */
UNIV_INLINE
hash_table_t*
btr_get_search_table(const dict_index_t* index);

/** The search info struct in an index */
struct btr_search_t{
	ulint	ref_count;	/*!< Number of blocks in this index tree
				that have search index built
				i.e. block->index points to this index.
				Protected by search latch except
				when during initialization in
				btr_search_info_create(). */

	/* @{ The following fields are not protected by any latch.
	Unfortunately, this means that they must be aligned to
	the machine word, i.e., they cannot be turned into bit-fields. */
	buf_block_t* root_guess;/*!< the root page frame when it was last time
				fetched, or NULL */
	ulint	withdraw_clock;	/*!< the withdraw clock value of the buffer
				pool when root_guess was stored */
	ulint	hash_analysis;	/*!< when this exceeds
				BTR_SEARCH_HASH_ANALYSIS, the hash
				analysis starts; this is reset if no
				success noticed */
	ibool	last_hash_succ;	/*!< TRUE if the last search would have
				succeeded, or did succeed, using the hash
				index; NOTE that the value here is not exact:
				it is not calculated for every search, and the
				calculation itself is not always accurate! */
	ulint	n_hash_potential;
				/*!< number of consecutive searches
				which would have succeeded, or did succeed,
				using the hash index;
				the range is 0 .. BTR_SEARCH_BUILD_LIMIT + 5 */
	/* @} */
	/*---------------------- @{ */
	ulint	n_fields;	/*!< recommended prefix length for hash search:
				number of full fields */
	ulint	n_bytes;	/*!< recommended prefix: number of bytes in
				an incomplete field
				@see BTR_PAGE_MAX_REC_SIZE */
	ibool	left_side;	/*!< TRUE or FALSE, depending on whether
				the leftmost record of several records with
				the same prefix should be indexed in the
				hash index */
	/*---------------------- @} */
#ifdef UNIV_SEARCH_PERF_STAT
	ulint	n_hash_succ;	/*!< number of successful hash searches thus
				far */
	ulint	n_hash_fail;	/*!< number of failed hash searches */
	ulint	n_patt_succ;	/*!< number of successful pattern searches thus
				far */
	ulint	n_searches;	/*!< number of searches */
#endif /* UNIV_SEARCH_PERF_STAT */
#ifdef UNIV_DEBUG
	ulint	magic_n;	/*!< magic number @see BTR_SEARCH_MAGIC_N */
/** value of btr_search_t::magic_n, used in assertions */
# define BTR_SEARCH_MAGIC_N	1112765
#endif /* UNIV_DEBUG */
};

/** The hash index system */
struct btr_search_sys_t{
	hash_table_t**	hash_tables;	/*!< the adaptive hash tables,
					mapping dtuple_fold values
					to rec_t pointers on index pages */
};

/** Latches protecting access to adaptive hash index. */
extern rw_lock_t**		btr_search_latches;

/** The adaptive hash index */
extern btr_search_sys_t*	btr_search_sys;

#ifdef UNIV_SEARCH_PERF_STAT
/** Number of successful adaptive hash index lookups */
extern ulint	btr_search_n_succ;
/** Number of failed adaptive hash index lookups */
extern ulint	btr_search_n_hash_fail;
#endif /* UNIV_SEARCH_PERF_STAT */

/** After change in n_fields or n_bytes in info, this many rounds are waited
before starting the hash analysis again: this is to save CPU time when there
is no hope in building a hash index. */
#define BTR_SEARCH_HASH_ANALYSIS	17

/** Limit of consecutive searches for trying a search shortcut on the search
pattern */
#define BTR_SEARCH_ON_PATTERN_LIMIT	3

/** Limit of consecutive searches for trying a search shortcut using
the hash index */
#define BTR_SEARCH_ON_HASH_LIMIT	3

/** We do this many searches before trying to keep the search latch
over calls from MySQL. If we notice someone waiting for the latch, we
again set this much timeout. This is to reduce contention. */
#define BTR_SEA_TIMEOUT			10000

#ifndef UNIV_NONINL
#include "btr0sea.ic"
#endif

#endif
