diff options
Diffstat (limited to 'storage/innobase/include/lock0lock.h')
| -rw-r--r-- | storage/innobase/include/lock0lock.h | 38 |
1 files changed, 36 insertions, 2 deletions
diff --git a/storage/innobase/include/lock0lock.h b/storage/innobase/include/lock0lock.h index a107359ccf1..40bb557a5b2 100644 --- a/storage/innobase/include/lock0lock.h +++ b/storage/innobase/include/lock0lock.h @@ -1,7 +1,7 @@ /***************************************************************************** -Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved. -Copyright (c) 2017, 2021, MariaDB Corporation. +Copyright (c) 1996, 2022, Oracle and/or its affiliates. +Copyright (c) 2017, 2022, MariaDB Corporation. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software @@ -151,6 +151,40 @@ lock_update_copy_and_discard( which copied */ const buf_block_t* block); /*!< in: index page; NOT the root! */ +/** Update gap locks between the last record of the left_block and the +first record of the right_block when a record is about to be inserted +at the start of the right_block, even though it should "naturally" be +inserted as the last record of the left_block according to the +current node pointer in the parent page. + +That is, we assume that the lowest common ancestor of the left_block +and right_block routes the key of the new record to the left_block, +but a heuristic which tries to avoid overflowing left_block has chosen +to insert the record into right_block instead. Said ancestor performs +this routing by comparing the key of the record to a "split point" - +all records greater or equal to than the split point (node pointer) +are in right_block, and smaller ones in left_block. +The split point may be smaller than the smallest key in right_block. + +The gap between the last record on the left_block and the first record +on the right_block is represented as a gap lock attached to the supremum +pseudo-record of left_block, and a gap lock attached to the new first +record of right_block. + +Thus, inserting the new record, and subsequently adjusting the node +pointers in parent pages to values smaller or equal to the new +records' key, will mean that gap will be sliced at a different place +("moved to the left"): fragment of the 1st gap will now become treated +as 2nd. Therefore, we must copy any GRANTED locks from 1st gap to the +2nd gap. Any WAITING locks must be of INSERT_INTENTION type (as no +other GAP locks ever wait for anything) and can stay at 1st gap, as +their only purpose is to notify the requester they can retry +insertion, and there's no correctness requirement to avoid waking them +up too soon. +@param left_block left page +@param right_block right page */ +void lock_update_node_pointer(const buf_block_t *left_block, + const buf_block_t *right_block); /*************************************************************//** Updates the lock table when a page is split to the left. */ void |