MDEV-35000 dict_table_close() is a performance hog

[dr-m]

• The Jira issue number for this PR is: MDEV-35000

Description

Every time dict_table_close() is decrementing the table reference count to 0, it is performing some expensive logic that aims to ensure that during FLUSH TABLES, the InnoDB persistent statistics will be deinitialized, so that during a subsequent ha_innobase::open() the statistics will be reloaded. The purpose of this is to ensure that FLUSH TABLES will make any changes to mysql.innodb_table_stats and mysql.innodb_index_stats accessible. This is an overkill, because FLUSH TABLES is executed very rarely.

There is a better way to do this: Keep track of FLUSH TABLES only, by overloading Handler_share::~Handler_share().

This also includes some preparation to simplify the initialization and clearing of the statistics:

innodb_stats_transient_sample_pages, innodb_stats_persistent_sample_pages: Change the type to UNSIGNED, because the number of pages in a table is limited to 32 bits by the InnoDB file formats.

btr_get_size_and_reserved(), fseg_get_n_frag_pages(), fseg_n_reserved_pages_low(), fseg_n_reserved_pages(): Return uint32_t. The file format limits page numbers to 32 bits.

dict_table_t::stat: An Atomic_relaxed<uint32_t> that combines a number of metadata fields.

innodb_copy_stat_flags(): Copy the statistics flags from TABLE_SHARE or HA_CREATE_INFO.

dict_table_t::stats_initialized(), dict_table_t::stats_is_persistent(): Accessors to dict_table_t::stat.

Release Notes

innodb_stats_transient_sample_pages, innodb_stats_persistent_sample_pages: Change the type to BIGINT UNSIGNED to UNSIGNED, because the number of pages in a table is limited to 32 bits by the InnoDB file formats.

How can this PR be tested?

This code is rather well covered by the regression test suite.

The FLUSH TABLES functionality with respect to InnoDB persistent staitistics is covered by the following tests:

• innodb.innodb_stats_auto_recalc_on_nonexistent
• innodb.innodb_stats_fetch

Basing the PR against the correct MariaDB version

• This is a new feature or a refactoring, and the PR is based against the main branch.
• This is a bug fix, and the PR is based against the earliest maintained branch in which the bug can be reproduced.

This is a performance bug fix. The way how the statistics are initialized and updated have been largely rewritten in MariaDB Server 10.6. It is not trivial to apply these changes to 10.5, which is fairly close to its End Of Life anyway.

PR quality check

• I checked the CODING_STANDARDS.md file and my PR conforms to this where appropriate.
• For any trivial modifications to the PR, I am ok with the reviewer making the changes themselves.

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