MDEV-36122 Assertion failure ctx0->old_table->get_ref_count() == 1 in ha_innobase::commit_inplace_alter_table()

[dr-m]

• The Jira issue number for this PR is: MDEV-36122

Description

trx_purge_close_tables(): Before releasing any metadata locks (MDL), release all table references, in case an ALTER TABLE…ALGORITHM=COPY operation has confused our logic.

trx_purge_table_acquire(), trx_purge_table_open(): Do not acquire any table reference before successfully acquiring a necessary metadata lock. In this way, if purge is waiting for MDL, a concurrent ha_innobase::commit_inplace_alter_table(commit=true) that is holding a conflicting MDL_EXCLUSIVE will only observe its own reference on the table that it may need to replace.

dict_table_open_on_id(): Simplify the logic.

dict_stats: A helper for acquiring MDL and opening the tables mysql.innodb_table_stats and mysql.innodb_index_stats.

innodb_ft_aux_table_validate(): Contiguously hold dict_sys.latch while accessing the table that we open with dict_table_open_on_name().

lock_table_children(): Do not hold a table reference while invoking dict_acquire_mdl_shared<false>(), which may temporarily release and reacquire the shared dict_sys.latch that we are holding.

prepare_inplace_alter_table_dict(): If an unexpected reference to the table exists, wait for the purge subsystem to release its table handle, similar to how we would do in case FULLTEXT INDEX existed. This function is supposed to be protected by MDL_EXCLUSIVE on the table name. If purge is going to access the table again later during is ALTER TABLE operation, it will have access to an MDL compatible name for it and therefore should conflict with any MDL_EXCLUSIVE that would cover ha_innobase::commit_inplace_alter_table(commit=true).

ha_innobase::rename_table(): Before locking the data dictionary, ensure that the purge subsystem is not holding a reference to the table due to the lack of metadata locking, related to FULLTEXT INDEX or the row-level undo logging of ALTER IGNORE TABLE.

With these changes, no caller of dict_acquire_mdl_shared<false> should be holding a table reference.

All remaining calls to dict_table_open_on_name(dict_locked=false) except the one in fts_lock_table() and possibly in the DDL recovery predicate innodb_check_version() should be protected by MDL, but there currently is no assertion that would enforce this.

Release Notes

Some race conditions between InnoDB internal table access and DDL were fixed.

How can this PR be tested?

Stress test by the RQG grammar that reproduced the assertion failures.

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 10.11 version of #3856.

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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