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Backported from 10.520e9e804c1and5948d7602e. sel_restore_position_for_mysql() moves forward persistent cursor position after btr_pcur_restore_position() call if cursor relative position is BTR_PCUR_ON and the cursor points to the record with NOT the same field values as in a stored record(and some other not important for this case conditions). It was done because btr_pcur_restore_position() sets page_cur_mode_t mode to PAGE_CUR_LE for cursor->rel_pos == BTR_PCUR_ON before opening cursor. So we are searching for the record less or equal to stored one. And if the found record is not equal to stored one, then it is less and we need to move cursor forward. But there can be a situation when the stored record was purged, but the new one with the same key but different value was inserted while row_search_mvcc() was suspended. In this case, when the thread is awaken, it will invoke sel_restore_position_for_mysql(), which, in turns, invoke btr_pcur_restore_position(), which will return false because found record don't match stored record, and sel_restore_position_for_mysql() will move forward cursor position. The above can lead to the case when awaken row_search_mvcc() do not see records inserted by other transactions while it slept. The mtr test case shows the example how it can be. The fix is to return special value from persistent cursor restoring function which would notify its caller that uniq fields of restored record and stored record are the same, and in this case sel_restore_position_for_mysql() don't move cursor forward. Delete-marked records are correctly processed in row_search_mvcc(). Non-unique secondary indexes are "uniquified" by adding the PK, the index->n_uniq should then be index->n_fields. So there is no need in additional checks in the fix. If transaction's readview can't see the changes made in secondary index record, it requests clustered index record in row_search_mvcc() to check its transaction id and get the correspondent record version. After this row_search_mvcc() commits mtr to preserve clustered index latching order, and starts mtr. Between those mtr commit and start secondary index pages are unlatched, and purge has the ability to remove stored in the cursor record, what causes rows duplication in result set for non-locking reads, as cursor position is restored to the previously visited record. To solve this the changes are just switched off for non-locking reads, it's quite simple solution, besides the changes don't make sense for non-locking reads. The more complex and effective from performance perspective solution is to create mtr savepoint before clustered record requesting and rolling back to that savepoint after that. See MDEV-27557. One more solution is to have per-record transaction id for secondary indexes. See MDEV-17598. If any of those is implemented, just remove select_lock_type argument in sel_restore_position_for_mysql().
560 lines
22 KiB
C
560 lines
22 KiB
C
/*****************************************************************************
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Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
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Copyright (c) 2017, 2021, MariaDB Corporation.
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This program is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free Software
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Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along with
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this program; if not, write to the Free Software Foundation, Inc.,
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51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA
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*****************************************************************************/
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/**************************************************//**
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@file include/btr0pcur.h
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The index tree persistent cursor
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Created 2/23/1996 Heikki Tuuri
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*******************************************************/
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#ifndef btr0pcur_h
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#define btr0pcur_h
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#include "dict0dict.h"
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#include "btr0cur.h"
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#include "buf0block_hint.h"
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#include "btr0btr.h"
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#include "gis0rtree.h"
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/* Relative positions for a stored cursor position */
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enum btr_pcur_pos_t {
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BTR_PCUR_ON = 1,
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BTR_PCUR_BEFORE = 2,
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BTR_PCUR_AFTER = 3,
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/* Note that if the tree is not empty, btr_pcur_store_position does not
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use the following, but only uses the above three alternatives, where the
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position is stored relative to a specific record: this makes implementation
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of a scroll cursor easier */
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BTR_PCUR_BEFORE_FIRST_IN_TREE = 4, /* in an empty tree */
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BTR_PCUR_AFTER_LAST_IN_TREE = 5 /* in an empty tree */
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};
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/**************************************************************//**
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Allocates memory for a persistent cursor object and initializes the cursor.
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@return own: persistent cursor */
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btr_pcur_t*
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btr_pcur_create_for_mysql(void);
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/*============================*/
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/**************************************************************//**
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Resets a persistent cursor object, freeing ::old_rec_buf if it is
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allocated and resetting the other members to their initial values. */
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void
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btr_pcur_reset(
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/*===========*/
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btr_pcur_t* cursor);/*!< in, out: persistent cursor */
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/**************************************************************//**
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Frees the memory for a persistent cursor object. */
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void
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btr_pcur_free_for_mysql(
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/*====================*/
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btr_pcur_t* cursor); /*!< in, own: persistent cursor */
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/**************************************************************//**
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Copies the stored position of a pcur to another pcur. */
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void
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btr_pcur_copy_stored_position(
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/*==========================*/
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btr_pcur_t* pcur_receive, /*!< in: pcur which will receive the
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position info */
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btr_pcur_t* pcur_donate); /*!< in: pcur from which the info is
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copied */
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/**************************************************************//**
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Sets the old_rec_buf field to NULL. */
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UNIV_INLINE
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void
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btr_pcur_init(
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/*==========*/
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btr_pcur_t* pcur); /*!< in: persistent cursor */
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/** Free old_rec_buf.
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@param[in] pcur Persistent cursor holding old_rec to be freed. */
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UNIV_INLINE
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void
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btr_pcur_free(
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btr_pcur_t* pcur);
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/**************************************************************//**
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Initializes and opens a persistent cursor to an index tree. It should be
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closed with btr_pcur_close. */
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UNIV_INLINE
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dberr_t
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btr_pcur_open_low(
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/*==============*/
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dict_index_t* index, /*!< in: index */
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ulint level, /*!< in: level in the btree */
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const dtuple_t* tuple, /*!< in: tuple on which search done */
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page_cur_mode_t mode, /*!< in: PAGE_CUR_L, ...;
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NOTE that if the search is made using a unique
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prefix of a record, mode should be
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PAGE_CUR_LE, not PAGE_CUR_GE, as the latter
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may end up on the previous page from the
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record! */
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ulint latch_mode,/*!< in: BTR_SEARCH_LEAF, ... */
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btr_pcur_t* cursor, /*!< in: memory buffer for persistent cursor */
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const char* file, /*!< in: file name */
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unsigned line, /*!< in: line where called */
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ib_uint64_t autoinc,/*!< in: PAGE_ROOT_AUTO_INC to be written
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(0 if none) */
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mtr_t* mtr); /*!< in: mtr */
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#define btr_pcur_open(i,t,md,l,c,m) \
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btr_pcur_open_low(i,0,t,md,l,c,__FILE__,__LINE__,0,m)
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/**************************************************************//**
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Opens an persistent cursor to an index tree without initializing the
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cursor. */
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UNIV_INLINE
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dberr_t
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btr_pcur_open_with_no_init_func(
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/*============================*/
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dict_index_t* index, /*!< in: index */
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const dtuple_t* tuple, /*!< in: tuple on which search done */
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page_cur_mode_t mode, /*!< in: PAGE_CUR_L, ...;
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NOTE that if the search is made using a unique
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prefix of a record, mode should be
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PAGE_CUR_LE, not PAGE_CUR_GE, as the latter
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may end up on the previous page of the
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record! */
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ulint latch_mode,/*!< in: BTR_SEARCH_LEAF, ...;
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NOTE that if ahi_latch then we might not
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acquire a cursor page latch, but assume
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that the ahi_latch protects the record! */
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btr_pcur_t* cursor, /*!< in: memory buffer for persistent cursor */
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#ifdef BTR_CUR_HASH_ADAPT
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rw_lock_t* ahi_latch,
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/*!< in: adaptive hash index latch held
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by the caller, or NULL if none */
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#endif /* BTR_CUR_HASH_ADAPT */
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const char* file, /*!< in: file name */
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unsigned line, /*!< in: line where called */
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mtr_t* mtr); /*!< in: mtr */
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#ifdef BTR_CUR_HASH_ADAPT
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# define btr_pcur_open_with_no_init(ix,t,md,l,cur,ahi,m) \
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btr_pcur_open_with_no_init_func(ix,t,md,l,cur,ahi,__FILE__,__LINE__,m)
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#else /* BTR_CUR_HASH_ADAPT */
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# define btr_pcur_open_with_no_init(ix,t,md,l,cur,ahi,m) \
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btr_pcur_open_with_no_init_func(ix,t,md,l,cur,__FILE__,__LINE__,m)
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#endif /* BTR_CUR_HASH_ADAPT */
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/*****************************************************************//**
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Opens a persistent cursor at either end of an index. */
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UNIV_INLINE
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dberr_t
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btr_pcur_open_at_index_side(
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/*========================*/
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bool from_left, /*!< in: true if open to the low end,
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false if to the high end */
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dict_index_t* index, /*!< in: index */
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ulint latch_mode, /*!< in: latch mode */
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btr_pcur_t* pcur, /*!< in/out: cursor */
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bool init_pcur, /*!< in: whether to initialize pcur */
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ulint level, /*!< in: level to search for
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(0=leaf) */
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mtr_t* mtr) /*!< in/out: mini-transaction */
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MY_ATTRIBUTE((nonnull));
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/**************************************************************//**
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Gets the up_match value for a pcur after a search.
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@return number of matched fields at the cursor or to the right if
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search mode was PAGE_CUR_GE, otherwise undefined */
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UNIV_INLINE
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ulint
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btr_pcur_get_up_match(
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/*==================*/
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const btr_pcur_t* cursor); /*!< in: persistent cursor */
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/**************************************************************//**
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Gets the low_match value for a pcur after a search.
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@return number of matched fields at the cursor or to the right if
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search mode was PAGE_CUR_LE, otherwise undefined */
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UNIV_INLINE
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ulint
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btr_pcur_get_low_match(
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/*===================*/
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const btr_pcur_t* cursor); /*!< in: persistent cursor */
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/**************************************************************//**
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If mode is PAGE_CUR_G or PAGE_CUR_GE, opens a persistent cursor on the first
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user record satisfying the search condition, in the case PAGE_CUR_L or
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PAGE_CUR_LE, on the last user record. If no such user record exists, then
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in the first case sets the cursor after last in tree, and in the latter case
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before first in tree. The latching mode must be BTR_SEARCH_LEAF or
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BTR_MODIFY_LEAF. */
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void
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btr_pcur_open_on_user_rec_func(
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/*===========================*/
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dict_index_t* index, /*!< in: index */
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const dtuple_t* tuple, /*!< in: tuple on which search done */
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page_cur_mode_t mode, /*!< in: PAGE_CUR_L, ... */
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ulint latch_mode, /*!< in: BTR_SEARCH_LEAF or
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BTR_MODIFY_LEAF */
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btr_pcur_t* cursor, /*!< in: memory buffer for persistent
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cursor */
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const char* file, /*!< in: file name */
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unsigned line, /*!< in: line where called */
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mtr_t* mtr); /*!< in: mtr */
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#define btr_pcur_open_on_user_rec(i,t,md,l,c,m) \
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btr_pcur_open_on_user_rec_func(i,t,md,l,c,__FILE__,__LINE__,m)
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/**********************************************************************//**
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Positions a cursor at a randomly chosen position within a B-tree.
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@return true if the index is available and we have put the cursor, false
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if the index is unavailable */
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UNIV_INLINE
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bool
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btr_pcur_open_at_rnd_pos_func(
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/*==========================*/
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dict_index_t* index, /*!< in: index */
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ulint latch_mode, /*!< in: BTR_SEARCH_LEAF, ... */
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btr_pcur_t* cursor, /*!< in/out: B-tree pcur */
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const char* file, /*!< in: file name */
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unsigned line, /*!< in: line where called */
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mtr_t* mtr); /*!< in: mtr */
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#define btr_pcur_open_at_rnd_pos(i,l,c,m) \
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btr_pcur_open_at_rnd_pos_func(i,l,c,__FILE__,__LINE__,m)
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/**************************************************************//**
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Frees the possible memory heap of a persistent cursor and sets the latch
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mode of the persistent cursor to BTR_NO_LATCHES.
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WARNING: this function does not release the latch on the page where the
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cursor is currently positioned. The latch is acquired by the
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"move to next/previous" family of functions. Since recursive shared locks
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are not allowed, you must take care (if using the cursor in S-mode) to
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manually release the latch by either calling
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btr_leaf_page_release(btr_pcur_get_block(&pcur), pcur.latch_mode, mtr)
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or by committing the mini-transaction right after btr_pcur_close().
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A subsequent attempt to crawl the same page in the same mtr would cause
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an assertion failure. */
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UNIV_INLINE
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void
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btr_pcur_close(
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/*===========*/
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btr_pcur_t* cursor); /*!< in: persistent cursor */
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/**************************************************************//**
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The position of the cursor is stored by taking an initial segment of the
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record the cursor is positioned on, before, or after, and copying it to the
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cursor data structure, or just setting a flag if the cursor id before the
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first in an EMPTY tree, or after the last in an EMPTY tree. NOTE that the
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page where the cursor is positioned must not be empty if the index tree is
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not totally empty! */
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void
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btr_pcur_store_position(
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/*====================*/
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btr_pcur_t* cursor, /*!< in: persistent cursor */
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mtr_t* mtr); /*!< in: mtr */
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#define btr_pcur_restore_position(l,cur,mtr) \
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(cur)->restore_position(l,__FILE__,__LINE__,mtr)
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/*********************************************************//**
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Gets the rel_pos field for a cursor whose position has been stored.
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@return BTR_PCUR_ON, ... */
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UNIV_INLINE
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ulint
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btr_pcur_get_rel_pos(
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/*=================*/
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const btr_pcur_t* cursor);/*!< in: persistent cursor */
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/**************************************************************//**
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Commits the mtr and sets the pcur latch mode to BTR_NO_LATCHES,
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that is, the cursor becomes detached.
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Function btr_pcur_store_position should be used before calling this,
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if restoration of cursor is wanted later. */
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UNIV_INLINE
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void
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btr_pcur_commit_specify_mtr(
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/*========================*/
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btr_pcur_t* pcur, /*!< in: persistent cursor */
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mtr_t* mtr); /*!< in: mtr to commit */
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/** Commits the mtr and sets the clustered index pcur and secondary index
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pcur latch mode to BTR_NO_LATCHES, that is, the cursor becomes detached.
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Function btr_pcur_store_position should be used for both cursor before
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calling this, if restoration of cursor is wanted later.
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@param[in] pcur persistent cursor
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@param[in] sec_pcur secondary index persistent cursor
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@param[in] mtr mtr to commit */
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UNIV_INLINE
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void
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btr_pcurs_commit_specify_mtr(
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btr_pcur_t* pcur,
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btr_pcur_t* sec_pcur,
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mtr_t* mtr);
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/*********************************************************//**
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Moves the persistent cursor to the next record in the tree. If no records are
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left, the cursor stays 'after last in tree'.
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@return TRUE if the cursor was not after last in tree */
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UNIV_INLINE
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ibool
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btr_pcur_move_to_next(
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/*==================*/
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btr_pcur_t* cursor, /*!< in: persistent cursor; NOTE that the
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function may release the page latch */
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mtr_t* mtr); /*!< in: mtr */
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/*********************************************************//**
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Moves the persistent cursor to the previous record in the tree. If no records
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are left, the cursor stays 'before first in tree'.
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@return TRUE if the cursor was not before first in tree */
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ibool
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btr_pcur_move_to_prev(
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/*==================*/
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btr_pcur_t* cursor, /*!< in: persistent cursor; NOTE that the
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function may release the page latch */
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mtr_t* mtr); /*!< in: mtr */
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/*********************************************************//**
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Moves the persistent cursor to the next user record in the tree. If no user
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records are left, the cursor ends up 'after last in tree'.
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@return TRUE if the cursor moved forward, ending on a user record */
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UNIV_INLINE
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ibool
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btr_pcur_move_to_next_user_rec(
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/*===========================*/
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btr_pcur_t* cursor, /*!< in: persistent cursor; NOTE that the
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function may release the page latch */
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mtr_t* mtr); /*!< in: mtr */
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/*********************************************************//**
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Moves the persistent cursor to the first record on the next page.
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Releases the latch on the current page, and bufferunfixes it.
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Note that there must not be modifications on the current page,
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as then the x-latch can be released only in mtr_commit. */
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void
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btr_pcur_move_to_next_page(
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/*=======================*/
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btr_pcur_t* cursor, /*!< in: persistent cursor; must be on the
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last record of the current page */
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mtr_t* mtr); /*!< in: mtr */
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#ifdef UNIV_DEBUG
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/*********************************************************//**
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Returns the btr cursor component of a persistent cursor.
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@return pointer to btr cursor component */
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UNIV_INLINE
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btr_cur_t*
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btr_pcur_get_btr_cur(
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/*=================*/
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const btr_pcur_t* cursor); /*!< in: persistent cursor */
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/*********************************************************//**
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Returns the page cursor component of a persistent cursor.
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@return pointer to page cursor component */
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UNIV_INLINE
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page_cur_t*
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btr_pcur_get_page_cur(
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/*==================*/
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const btr_pcur_t* cursor); /*!< in: persistent cursor */
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/*********************************************************//**
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Returns the page of a persistent cursor.
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@return pointer to the page */
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UNIV_INLINE
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page_t*
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btr_pcur_get_page(
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/*==============*/
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const btr_pcur_t* cursor);/*!< in: persistent cursor */
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/*********************************************************//**
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Returns the buffer block of a persistent cursor.
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@return pointer to the block */
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UNIV_INLINE
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buf_block_t*
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btr_pcur_get_block(
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/*===============*/
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const btr_pcur_t* cursor);/*!< in: persistent cursor */
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/*********************************************************//**
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Returns the record of a persistent cursor.
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@return pointer to the record */
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UNIV_INLINE
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rec_t*
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btr_pcur_get_rec(
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/*=============*/
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const btr_pcur_t* cursor);/*!< in: persistent cursor */
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#else /* UNIV_DEBUG */
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# define btr_pcur_get_btr_cur(cursor) (&(cursor)->btr_cur)
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# define btr_pcur_get_page_cur(cursor) (&(cursor)->btr_cur.page_cur)
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# define btr_pcur_get_page(cursor) ((cursor)->btr_cur.page_cur.block->frame)
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# define btr_pcur_get_block(cursor) ((cursor)->btr_cur.page_cur.block)
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# define btr_pcur_get_rec(cursor) ((cursor)->btr_cur.page_cur.rec)
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#endif /* UNIV_DEBUG */
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/*********************************************************//**
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Checks if the persistent cursor is on a user record. */
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UNIV_INLINE
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ibool
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btr_pcur_is_on_user_rec(
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/*====================*/
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const btr_pcur_t* cursor);/*!< in: persistent cursor */
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/*********************************************************//**
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Checks if the persistent cursor is after the last user record on
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a page. */
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UNIV_INLINE
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ibool
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btr_pcur_is_after_last_on_page(
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/*===========================*/
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const btr_pcur_t* cursor);/*!< in: persistent cursor */
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/*********************************************************//**
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Checks if the persistent cursor is before the first user record on
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a page. */
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UNIV_INLINE
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|
ibool
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btr_pcur_is_before_first_on_page(
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/*=============================*/
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const btr_pcur_t* cursor);/*!< in: persistent cursor */
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/*********************************************************//**
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|
Checks if the persistent cursor is before the first user record in
|
|
the index tree. */
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static inline bool btr_pcur_is_before_first_in_tree(btr_pcur_t* cursor);
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|
/*********************************************************//**
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|
Checks if the persistent cursor is after the last user record in
|
|
the index tree. */
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|
static inline bool btr_pcur_is_after_last_in_tree(btr_pcur_t* cursor);
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|
/*********************************************************//**
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|
Moves the persistent cursor to the next record on the same page. */
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|
UNIV_INLINE
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|
void
|
|
btr_pcur_move_to_next_on_page(
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|
/*==========================*/
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|
btr_pcur_t* cursor);/*!< in/out: persistent cursor */
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|
/*********************************************************//**
|
|
Moves the persistent cursor to the previous record on the same page. */
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|
UNIV_INLINE
|
|
void
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|
btr_pcur_move_to_prev_on_page(
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|
/*==========================*/
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|
btr_pcur_t* cursor);/*!< in/out: persistent cursor */
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|
/*********************************************************//**
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|
Moves the persistent cursor to the infimum record on the same page. */
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|
UNIV_INLINE
|
|
void
|
|
btr_pcur_move_before_first_on_page(
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|
/*===============================*/
|
|
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. */
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|
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(0), 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 latch_mode BTR_SEARCH_LEAF, ...
|
|
@param file file name
|
|
@param line line where called
|
|
@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, const char *file,
|
|
unsigned line, mtr_t *mtr);
|
|
};
|
|
|
|
#include "btr0pcur.inl"
|
|
|
|
#endif
|