This is important since Sys_var_typelib and its descendants return
pointers to constant symbols from *_value_ptr, which are situated in
write-protected-memory.
* functions const-qualified:
- value_ptr
- session_value_ptr
- global_value_ptr
- default_value_ptr
- Sys_var_vers_asof::value_ptr
- other minor private ones
* remove C-style typecasts when it discards qualifiers
MDEV-16026: Forbid global system_versioning_asof in non-default time zone
* store `system_versioning_asof` in unix time;
* both session and global vars are processed in session timezone;
* setting `default` does not copy global variable anymore. Instead, it sets
system_time to SYSTEM_TIME_UNSPECIFIED, which means that no 'AS OF' time
is applied and `now()` can be assumed
As a regression, we cannot assign values below 1970 (UTC) anymore
MDEV-16481: set global system_versioning_asof=sf() crashes in specific case
* sys_vars.h: add `MYSQL_TIME` field to `set_var::save_result`
* sys_vars.ic: get rid of calling `var->value->get_date()` from
`Sys_var_vers_asof::update()`
* versioning.sysvars: add test; remove double warning
refactor Sys_var_vers_asof
* inherit from sys_var rather than Sys_var_enum
* remove junk "DEFAULT" keyword. There is DEFAULT in SQL grammar for it.
* make all conversions in check() to avoid possible errors
* avoid double var->value evaluation, which could
consequence in undefined behavior
The code in vers_select_conds_t::init_from_sysvar() assumed that
the value of the system_versioning_asof is DATETIME.
But it also could be DATE after a query like this:
SET system_versioning_asof = DATE(NOW());
Fixing Sys_var_vers_asof::update() to convert the value
of the assignment source to DATETIME if it returned DATE.
Now vers_select_conds_t::init_from_sysvar() always gets a DATETIME value.
Simplifying definitions on Sys_var_charptr*:
- Removing sys_var::is_os_charset
- Adding a new class Sys_var_charptr_fscs, to handle system
variables with character_set_filesystem.
For release builds, do not declare unused variables.
unpack_row(): Omit a debug-only variable from WSREP diagnostic message.
create_wsrep_THD(): Fix -Wmaybe-uninitialized for the PSI_thread_key.
When enabling system variables tracker, make a copy of
global_system_variables.session_track_system_variables
under LOCK_global_system_variables. This protects from concurrent variable
updates and potential freed memory access, as well as from variable
reconstruction (which was previously protected by LOCK_plugin).
We can also use this copy as a session variable pointer, so that we don't
have to allocate memory and reconstruct it every time it is referenced.
For this very reason we don't need buffer_length stuff anymore.
As well as don't we need to take LOCK_plugin early in ::enable().
Unified ::parse_var_list() to acquire LOCK_plugin unconditionally.
For no apparent reason it wasn't previously acquired for global
variable update.
Part of MDEV-14984 - regression in connect performance
One less new/delete per connection.
Removed m_mem_flag since most allocs are thread specific. The only
exception are allocs performed during initialization.
Removed State_tracker and Session_tracker constructors as they don't make
sense anymore.
No reason to access session_sysvars_tracker via get_tracker(), so access
it directly instead.
Part of MDEV-14984 - regression in connect performance
