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
The test that was added in commit e05650e686
would break a subsequent run of a test encryption.innodb-bad-key-change
because some pages in the system tablespace would be encrypted with
a different key.
The failure was repeatable with the following invocation:
./mtr --no-reorder \
encryption.create_or_replace,cbc \
encryption.innodb-bad-key-change,cbc
Because the crash was unrelated to the code changes that we reverted
in commit eb38b1f703
we can safely re-apply those fixes.
Let us shrink the test encryption.create_or_replace so that it can
run on the CI system, also on the embedded server.
encryption.create_or_replace_big: Renamed from the original test,
with the subset of encryption.create_or_replace omitted.
Analysis: There is race between drop table and encryption threads that
could cause encryption thread to enter mutex that has been already
released.
Fix: When destroying crypt_data first enter the mutex and set crypt data
unavailable, then release the memory and clean up the data. This should
make the race more unprobable. Additionally, added big_test for
create_or_replace as it could fail testcase timeout
if you have slow I/O (tested that testcase passes with --mem).
Test create_or_replace should make sure that background decrypt
operation is finished and flush all dirty pages using restart
to clean up the database before ending.
* support statically compiled file_key_management when possible
* rename encryption.encryption_create_or_replace -> encryption.create_or_replace
* delete unnecessary *.opt file (including
have_key_management_plugin.inc is enough)
* remove unnecessary LOWER() for strings that are compared
case insensitively anyway
