Fix spider init bugs (MDEV-22979, MDEV-27233, MDEV-28218) while
preventing regression on old ones (MDEV-30370, MDEV-29904)
Two things are changed:
First, Spider initialisation is made fully synchronous, i.e. it no
longer happens in a background thread. Adapted from the original fix
by nayuta for MDEV-27233. This change itself would cause failure when
spider is initialised early, by plugin-load-add, due to dependency on
Aria and udf function creation, which are fixed in the second and
third parts below. Requires SQL Service, thus porting earlier versions
requires MDEV-27595
Second, if spider is initialised before udf_init(), create udf by
inserting into `mysql.func`, otherwise do it by `CREATE FUNCTION` as
usual. This change may be generalised in MDEV-31401.
Also factor out some clean-up queries from deinit_spider.inc for use
of spider init tests.
A minor caveat is that early spider initialisation will fail if the
server is bootstrapped for the first time, due to missing `mysql`
database which needs to be created by the bootstrap script.
Removing procedures that were created and dropped during init.
This also fixes a race condition where mtr test with
plugin-load-add=ha_spider.so causes post test check to fail as it
expects the procedures to still be there.
MDEV-27095 installing one spider plugin should not trigger others
There are several plugins in ha_spider: spider, spider_alloc_mem,
spider_wrapper_protocols, spider_rewrite etc.
INSTALL PLUGIN foo SONAME ha_spider causes all the other ones to be
installed by the init queries where foo is any of the plugins.
This introduces unnecessary complexiy. For example it reads
mysql.plugins to find all other plugins, causing the hack of moving
spider plugin init to a separate thread.
To install all spider related plugins, install soname ha_spider should
be used instead.
This also fixes spurious rows in mysql.plugin when installing say only
the spider plugin with `plugin-load-add=SPIDER=ha_spider.so`:
select * from mysql.plugin;
name dl
spider_alloc_mem ha_spider.so # should not be here
spider_wrapper_protocols ha_spider.so # should not be here
Adapted from part of the reverted commit
c160a115b8b6dcd54bb3daf1a751ee9c68b7ee47.
We introduce simple plugin dependency. A plugin init function may
return HA_ERR_RETRY_INIT. If this happens during server startup when
the server is trying to initialise all plugins, the failed plugins
will be retried, until no more plugins succeed in initialisation or
want to be retried.
This will fix spider init bugs which is caused in part by its
dependency on Aria for initialisation.
The reason we need a new return code, instead of treating every
failure as a request for retry, is that it may be impossible to clean
up after a failed plugin initialisation. Take InnoDB for example, it
has a global variable `buf_page_cleaner_is_active`, which may not
satisfy an assertion during a second initialisation try, probably
because InnoDB does not expect the initialisation to be called
twice. A test that may fail because of this is
`encryption.corrupted_during_recovery`, see for example[1], which is
tested at 73835f64b7fc245d38812380685aca03bef72bb5, a previous commit
where we retry every failed plugin.
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.
