Remove one of the major sources of race condiitons in mariadb-test.
Normally, mariadb_close() sends COM_QUIT to the server and immediately
disconnects. In mariadb-test it means the test can switch to another
connection and sends queries to the server before the server even
started parsing the COM_QUIT packet and these queries can see the
connection as fully active, as it didn't reach dispatch_command yet.
This is a major source of instability in tests and many - but not all,
still less than a half - tests employ workarounds. The correct one
is a pair count_sessions.inc/wait_until_count_sessions.inc.
Also very popular was wait_until_disconnected.inc, which was completely
useless, because it verifies that the connection is closed, and after
disconnect it always is, it didn't verify whether the server processed
COM_QUIT. Sadly the placebo was as widely used as the real thing.
Let's fix this by making mariadb-test `disconnect` command _to wait_ for
the server to confirm. This makes almost all workarounds redundant.
In some cases count_sessions.inc/wait_until_count_sessions.inc is still
needed, though, as only `disconnect` command is changed:
* after external tools, like `exec $MYSQL`
* after failed `connect` command
* replication, after `STOP SLAVE`
* Federated/CONNECT/SPIDER/etc after `DROP TABLE`
and also in some XA tests, because an XA transaction is dissociated from
the THD very late, after the server has closed the client connection.
Collateral cleanups: fix comments, remove some redundant statements:
* DROP IF EXISTS if nothing is known to exist
* DROP table/view before DROP DATABASE
* REVOKE privileges before DROP USER
etc
row_purge_remove_sec_if_poss_leaf(): If there is an active transaction
that is not newer than PAGE_MAX_TRX_ID, return the bogus value 1
so that row_purge_remove_sec_if_poss_tree() is guaranteed to recheck if
the record needs to be purged. It could be the case that an active
transaction would insert this record between the time this check
completed and row_purge_remove_sec_if_poss_tree() acquired a latch
on the secondary index leaf page again.
row_purge_del_mark_error(), row_purge_check(): Some unlikely code
refactored into separate non-inline functions.
trx_sys_t::find_same_or_older_low(): Move the unlikely and bulky
part of trx_sys_t::find_same_or_older() to a non-inline function.
trx_sys_t::find_same_or_older_in_purge(): A variant of
trx_sys_t::find_same_or_older() for use in the purge subsystem,
with potential concurrent access of the same trx_t object from
multiple threads.
trx_t::max_inactive_id_atomic: An Atomic_relaxed alias of the
regular data field trx_t::max_inactive_id, which we
use on systems that have native 64-bit loads or stores.
On any 64-bit system that seems to be supported by GCC, Clang or MSVC,
relaxed atomic loads and stores use the regular load and store
instructions. On -march=i686 the 64-bit atomic loads and stores
would use an XMM register.
This fixes a regression that had been introduced in
commit b7b9f3ce82 (MDEV-34515).
There would be messages
[ERROR] InnoDB: tried to purge non-delete-marked record in index
in the server error log, and an assertion ut_ad(0) would cause a
crash of debug instrumented builds. This could also cause incorrect
results for MVCC reads and corrupted secondary indexes.
The debug instrumented test case was written by Debarun Banerjee.
Reviewed by: Debarun Banerjee
