spider_db_mbase_util::open_item_func() is a monster function.
It is difficult to maintain while it is expected that we need to
modify it when a new SQL function or a new func_type is added.
We split the function into two distinct functions: one handles the
case of str != NULL and the other handles the case of str == NULL.
This refactoring was done in a conservative way because we do not
have comprehensive tests on the function.
It also fixes MDEV-29447 and MDEV-31338 where field items that are
arguments of a func item may be used before created / initialised.
Note this commit is adapted from a patch by Nayuta for MDEV-26285.
MDEV-31487: Recovery or backup failure after innodb_undo_log_truncate=ON
recv_sys_t::parse(): For undo tablespace truncation mini-transactions,
remember the start_lsn instead of the end LSN. This is what we expect
after commit 461402a56432fa5cd0f6d53118ccce23081fca18 (MDEV-30479).
MDEV-31479: Inconsistency between MRR and SQL layer costs can cause poor query plan
(Same as
TODO-3938: best_access_path shows negative costs for mrr=on)
best_access_path() assumes that quick select cost includes
(quick->rows/TIME_FOR_COMPARE) as a cost of checking the attached
part of the WHERE condition.
It calls adjust_quick_cost() to subtract addition from quick's cost.
The problem was that DS-MRR cost formula didn't include this cost.
For very large tables, adjust_quick_cost() would produce a negative
cost which would cause assert in debug build or bad query plan choice
in release builds.
MDEV-31442 page_cleaner thread aborts while releasing the tablespace
After further I/O on a tablespace has been stopped
(for example due to DROP TABLE or an operation that
rebuilds a table), page cleaner thread tries to
flush the pending writes for the tablespace and
releases the tablespace reference even though it was not
acquired.
fil_space_t::flush(): Don't release the tablespace when it is
being stopped and closed
