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b7b9f3ce82
In a Sysbench oltp_update_index workload that involves 1 table,
a serious contention between the workload and the purge of history
was observed. This was the worst when the table contained only 1 record.
This turned out to be fixed by setting innodb_purge_batch_size=128,
which corresponds to the number of usable persistent rollback segments.
When we go above that, there would be contention between row_purge_poss_sec()
and the workload, typically on the clustered index page latch, sometimes
also on a secondary index page latch. It might be that with smaller
batches, trx_sys.history_size() will end up pausing all concurrent
transaction start/commit frequently enough so that purge will be able
to make some progress, so that there would be less contention on the
index page latches between purge and SQL execution.
In commit aa719b5010 (part of MDEV-32050)
the interpretation of the parameter innodb_purge_batch_size was slightly
changed. It would correspond to the maximum desired size of the
purge_sys.pages cache. Before that change, the parameter was referring to
a number of undo log pages, but the accounting might have been inaccurate.
To avoid a regression, we will reduce the default value to
innodb_purge_batch_size=127, which will also be compatible with
innodb_undo_tablespaces>1 (which will disable rollback segment 0).
Additionally, some logic in the purge and MVCC checks is simplified.
The purge tasks will make use of purge_sys.pages when accessing undo
log pages to find out if a secondary index record can be removed.
If an undo page needs to be looked up in buf_pool.page_hash, we will
merely buffer-fix it. This is correct, because the undo pages are
append-only in nature. Holding purge_sys.latch or purge_sys.end_latch
or the fact that the current thread is executing as a part of an
in-progress purge batch will prevent the contents of the undo page from
being freed and subsequently reused. The buffer-fix will prevent the
page from being evicted form the buffer pool. Thanks to this logic,
we can refer to the undo log record directly in the buffer pool page
and avoid copying the record.
buf_pool_t::page_fix(): Look up and buffer-fix a page. This is useful
for accessing undo log pages, which are append-only by nature.
There will be no need to deal with change buffer or ROW_FORMAT=COMPRESSED
in that case.
purge_sys_t::view_guard::view_guard(): Allow the type of guard to be
acquired: end_latch, latch, or no latch (in case we are a purge thread).
purge_sys_t::view_guard::get(): Read-only accessor to purge_sys.pages.
purge_sys_t::get_page(): Invoke buf_pool_t::page_fix().
row_vers_old_has_index_entry(): Replaced with row_purge_is_unsafe()
and row_undo_mod_sec_unsafe().
trx_undo_get_undo_rec(): Merged to trx_undo_prev_version_build().
row_purge_poss_sec(): Add the parameter mtr and remove redundant
or unused parameters sec_pcur, sec_mtr, is_tree. We will use the
caller's mtr object but release any acquired page latches before
returning.
btr_cur_get_page(), page_cur_get_page(): Do not invoke page_align().
row_purge_remove_sec_if_poss_leaf(): Return the value of PAGE_MAX_TRX_ID
to be checked against the page in row_purge_remove_sec_if_poss_tree().
If the secondary index page was not changed meanwhile, it will be
unnecessary to invoke row_purge_poss_sec() again.
trx_undo_prev_version_build(): Access any undo log pages using
the caller's mini-transaction object.
row_purge_vc_matches_cluster(): Moved to the only compilation unit that
needs it.
Reviewed by: Debarun Banerjee
295 lines
12 KiB
C
295 lines
12 KiB
C
/*****************************************************************************
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Copyright (c) 1994, 2016, Oracle and/or its affiliates. All Rights Reserved.
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Copyright (c) 2018, 2022, 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/page0cur.h
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The page cursor
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Created 10/4/1994 Heikki Tuuri
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*************************************************************************/
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#ifndef page0cur_h
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#define page0cur_h
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#include "page0page.h"
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#ifdef UNIV_DEBUG
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/*********************************************************//**
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Gets pointer to the buffer block where the cursor is positioned.
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@return page */
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UNIV_INLINE
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buf_block_t*
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page_cur_get_block(
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/*===============*/
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page_cur_t* cur); /*!< in: page cursor */
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/*********************************************************//**
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Gets pointer to the page frame where the cursor is positioned.
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@return page */
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UNIV_INLINE
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page_zip_des_t*
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page_cur_get_page_zip(
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/*==================*/
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page_cur_t* cur); /*!< in: page cursor */
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/* Gets the record where the cursor is positioned.
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@param cur page cursor
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@return record */
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UNIV_INLINE
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rec_t *page_cur_get_rec(const page_cur_t *cur);
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#else /* UNIV_DEBUG */
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# define page_cur_get_block(cur) (cur)->block
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# define page_cur_get_page_zip(cur) buf_block_get_page_zip((cur)->block)
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# define page_cur_get_rec(cur) (cur)->rec
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#endif /* UNIV_DEBUG */
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#define page_cur_get_page(cur) page_cur_get_block(cur)->page.frame
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#define is_page_cur_get_page_zip(cur) is_buf_block_get_page_zip((cur)->block)
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/*********************************************************//**
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Sets the cursor object to point before the first user record
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on the page. */
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UNIV_INLINE
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void
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page_cur_set_before_first(
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/*======================*/
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const buf_block_t* block, /*!< in: index page */
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page_cur_t* cur); /*!< in: cursor */
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/*********************************************************//**
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Sets the cursor object to point after the last user record on
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the page. */
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UNIV_INLINE
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void
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page_cur_set_after_last(
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/*====================*/
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const buf_block_t* block, /*!< in: index page */
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page_cur_t* cur); /*!< in: cursor */
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/*********************************************************//**
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Returns TRUE if the cursor is before first user record on page.
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@return TRUE if at start */
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UNIV_INLINE
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ibool
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page_cur_is_before_first(
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/*=====================*/
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const page_cur_t* cur); /*!< in: cursor */
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/*********************************************************//**
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Returns TRUE if the cursor is after last user record.
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@return TRUE if at end */
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UNIV_INLINE
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ibool
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page_cur_is_after_last(
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/*===================*/
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const page_cur_t* cur); /*!< in: cursor */
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/**********************************************************//**
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Positions the cursor on the given record. */
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UNIV_INLINE
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void
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page_cur_position(
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/*==============*/
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const rec_t* rec, /*!< in: record on a page */
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const buf_block_t* block, /*!< in: buffer block containing
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the record */
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page_cur_t* cur); /*!< out: page cursor */
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/***********************************************************//**
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Inserts a record next to page cursor. Returns pointer to inserted record if
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succeed, i.e., enough space available, NULL otherwise. The cursor stays at
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the same logical position, but the physical position may change if it is
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pointing to a compressed page that was reorganized.
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IMPORTANT: The caller will have to update IBUF_BITMAP_FREE
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if this is a compressed leaf page in a secondary index.
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This has to be done either within the same mini-transaction,
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or by invoking ibuf_reset_free_bits() before mtr_commit().
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@return pointer to record if succeed, NULL otherwise */
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UNIV_INLINE
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rec_t*
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page_cur_tuple_insert(
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/*==================*/
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page_cur_t* cursor, /*!< in/out: a page cursor */
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const dtuple_t* tuple, /*!< in: pointer to a data tuple */
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rec_offs** offsets,/*!< out: offsets on *rec */
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mem_heap_t** heap, /*!< in/out: pointer to memory heap, or NULL */
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ulint n_ext, /*!< in: number of externally stored columns */
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mtr_t* mtr) /*!< in/out: mini-transaction */
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MY_ATTRIBUTE((nonnull, warn_unused_result));
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/***********************************************************//**
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Inserts a record next to page cursor on an uncompressed page.
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@return pointer to record
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@retval nullptr if not enough space was available */
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rec_t*
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page_cur_insert_rec_low(
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/*====================*/
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const page_cur_t*cur, /*!< in: page cursor */
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const rec_t* rec, /*!< in: record to insert after cur */
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rec_offs* offsets,/*!< in/out: rec_get_offsets(rec, index) */
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mtr_t* mtr) /*!< in/out: mini-transaction */
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MY_ATTRIBUTE((nonnull, warn_unused_result));
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/***********************************************************//**
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Inserts a record next to page cursor on a compressed and uncompressed
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page.
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IMPORTANT: The caller will have to update IBUF_BITMAP_FREE
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if this is a compressed leaf page in a secondary index.
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This has to be done either within the same mini-transaction,
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or by invoking ibuf_reset_free_bits() before mtr_commit().
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@return pointer to inserted record
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@return nullptr on failure */
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rec_t*
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page_cur_insert_rec_zip(
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/*====================*/
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page_cur_t* cursor, /*!< in/out: page cursor,
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logical position unchanged */
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const rec_t* rec, /*!< in: pointer to a physical record */
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rec_offs* offsets,/*!< in/out: rec_get_offsets(rec, index) */
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mtr_t* mtr) /*!< in/out: mini-transaction */
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MY_ATTRIBUTE((nonnull, warn_unused_result));
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/***********************************************************//**
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Deletes a record at the page cursor. The cursor is moved to the
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next record after the deleted one. */
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void
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page_cur_delete_rec(
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/*================*/
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page_cur_t* cursor, /*!< in/out: a page cursor */
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const rec_offs* offsets,/*!< in: rec_get_offsets(
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cursor->rec, index) */
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mtr_t* mtr) /*!< in/out: mini-transaction */
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MY_ATTRIBUTE((nonnull));
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/** Apply a INSERT_HEAP_REDUNDANT or INSERT_REUSE_REDUNDANT record that was
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written by page_cur_insert_rec_low() for a ROW_FORMAT=REDUNDANT page.
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@param block B-tree or R-tree page in ROW_FORMAT=COMPACT or DYNAMIC
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@param reuse false=allocate from PAGE_HEAP_TOP; true=reuse PAGE_FREE
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@param prev byte offset of the predecessor, relative to PAGE_OLD_INFIMUM
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@param enc_hdr encoded fixed-size header bits
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@param hdr_c number of common record header bytes with prev
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@param data_c number of common data bytes with prev
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@param data literal header and data bytes
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@param data_len length of the literal data, in bytes
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@return whether the operation failed (inconcistency was noticed) */
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bool page_apply_insert_redundant(const buf_block_t &block, bool reuse,
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ulint prev, ulint enc_hdr,
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size_t hdr_c, size_t data_c,
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const void *data, size_t data_len);
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/** Apply a INSERT_HEAP_DYNAMIC or INSERT_REUSE_DYNAMIC record that was
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written by page_cur_insert_rec_low() for a ROW_FORMAT=COMPACT or DYNAMIC page.
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@param block B-tree or R-tree page in ROW_FORMAT=COMPACT or DYNAMIC
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@param reuse false=allocate from PAGE_HEAP_TOP; true=reuse PAGE_FREE
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@param prev byte offset of the predecessor, relative to PAGE_NEW_INFIMUM
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@param shift unless !reuse: number of bytes the PAGE_FREE is moving
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@param enc_hdr_l number of copied record header bytes, plus record type bits
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@param hdr_c number of common record header bytes with prev
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@param data_c number of common data bytes with prev
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@param data literal header and data bytes
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@param data_len length of the literal data, in bytes
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@return whether the operation failed (inconcistency was noticed) */
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bool page_apply_insert_dynamic(const buf_block_t &block, bool reuse,
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ulint prev, ulint shift, ulint enc_hdr_l,
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size_t hdr_c, size_t data_c,
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const void *data, size_t data_len);
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/** Apply a DELETE_ROW_FORMAT_REDUNDANT record that was written by
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page_cur_delete_rec() for a ROW_FORMAT=REDUNDANT page.
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@param block B-tree or R-tree page in ROW_FORMAT=REDUNDANT
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@param prev byte offset of the predecessor, relative to PAGE_OLD_INFIMUM
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@return whether the operation failed (inconcistency was noticed) */
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bool page_apply_delete_redundant(const buf_block_t &block, ulint prev);
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/** Apply a DELETE_ROW_FORMAT_DYNAMIC record that was written by
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page_cur_delete_rec() for a ROW_FORMAT=COMPACT or DYNAMIC page.
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@param block B-tree or R-tree page in ROW_FORMAT=COMPACT or DYNAMIC
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@param prev byte offset of the predecessor, relative to PAGE_NEW_INFIMUM
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@param hdr_size record header size, excluding REC_N_NEW_EXTRA_BYTES
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@param data_size data payload size, in bytes
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@return whether the operation failed (inconcistency was noticed) */
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bool page_apply_delete_dynamic(const buf_block_t &block, ulint prev,
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size_t hdr_size, size_t data_size);
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MY_ATTRIBUTE((warn_unused_result))
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/****************************************************************//**
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Searches the right position for a page cursor. */
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bool
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page_cur_search_with_match(
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/*=======================*/
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const dtuple_t* tuple, /*!< in: data tuple */
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page_cur_mode_t mode, /*!< in: PAGE_CUR_L,
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PAGE_CUR_LE, PAGE_CUR_G, or
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PAGE_CUR_GE */
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ulint* iup_matched_fields,
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/*!< in/out: already matched
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fields in upper limit record */
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ulint* ilow_matched_fields,
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/*!< in/out: already matched
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fields in lower limit record */
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page_cur_t* cursor, /*!< in/out: page cursor */
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rtr_info_t* rtr_info);/*!< in/out: rtree search stack */
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#ifdef BTR_CUR_HASH_ADAPT
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MY_ATTRIBUTE((warn_unused_result))
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/** Search the right position for a page cursor.
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@param[in] tuple key to be searched for
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@param[in] mode search mode
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@param[in,out] iup_matched_fields already matched fields in the
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upper limit record
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@param[in,out] iup_matched_bytes already matched bytes in the
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first partially matched field in the upper limit record
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@param[in,out] ilow_matched_fields already matched fields in the
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lower limit record
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@param[in,out] ilow_matched_bytes already matched bytes in the
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first partially matched field in the lower limit record
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@param[in,out] cursor page cursor */
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bool
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page_cur_search_with_match_bytes(
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const dtuple_t* tuple,
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page_cur_mode_t mode,
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ulint* iup_matched_fields,
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ulint* iup_matched_bytes,
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ulint* ilow_matched_fields,
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ulint* ilow_matched_bytes,
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page_cur_t* cursor);
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#endif /* BTR_CUR_HASH_ADAPT */
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/***********************************************************//**
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Positions a page cursor on a randomly chosen user record on a page. If there
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are no user records, sets the cursor on the infimum record. */
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void page_cur_open_on_rnd_user_rec(page_cur_t *cursor);
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/** Index page cursor */
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struct page_cur_t{
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dict_index_t* index;
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rec_t* rec; /*!< pointer to a record on page */
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rec_offs* offsets;
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buf_block_t* block; /*!< pointer to the block containing rec */
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};
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MY_ATTRIBUTE((nonnull, warn_unused_result))
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inline rec_t *page_cur_move_to_next(page_cur_t *cur)
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{
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return cur->rec= page_rec_get_next(cur->rec);
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}
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MY_ATTRIBUTE((nonnull, warn_unused_result))
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inline rec_t *page_cur_move_to_prev(page_cur_t *cur)
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{
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return cur->rec= page_rec_get_prev(cur->rec);
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}
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#include "page0cur.inl"
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#endif
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